Manchester Ship Canal - Strategic Review of Fish Populations

UNITED UTILITIES

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MANCHESTER SHIP CANAL STRATEGIC REVIEW OF FISH POPULATIONS

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FINAL REPORT

September 2007

APEM REF:

410039

CLIENT:

United Utilities

ADDRESS:

Haweswater House, Lingley Mere Business Park, Lingley Green Avenue, Great Sankey, Warrington, WA5 3LP

PROJECT No:

410039

DATE OF ISSUE:

September 2007

PROJECT DIRECTOR:

Dr. Keith Hendry

PROJECT MANAGER:

David Campbell, M.Sc.

SENIOR SCIENTIST:

Adrian Pinder Dr. Keith Hendry

Riverview, Embankment Business Park, Heaton Mersey, Stockport, SK4 3GN Tel: 0161 442 8938 Fax: 0161 432 6083 Website: www.apemltd.co.uk Registered in England No. 2530851

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EXECUTIVE SUMMARY Since the onset of the industrial revolution, the River Mersey has been subject to intense ecological stress from a number of sources. Hence, until the mid 1980s the Mersey and its estuary were infamous as being one of the most grossly polluted waterways in Europe. With the primary pollutants being derived from domestic and industrial effluents, the physical alteration to the natural hydraulics of the system imposed when building the Manchester Ship Canal have also been responsible for amplifying the issues associated with poor water quality. Over the last 20 years, enormous improvements in water quality have been achieved throughout the basin, which has driven a concomitant increase in general ecological health and the partial recovery of fish populations. Although these improvements are very much tangible, the future recovery and long-term development of fish populations is still heavily constrained by ongoing water quality issues and a legacy of historical pollution and physical engineering. Since its opening in 1894, the Manchester Ship Canal (MSC) has played a central role in governing the ecological functioning of the Mersey Basin and due to the morphological characteristics of this water-body, will continue to impact on the recovery of fish populations for the foreseeable future. Water quality in many of the peripheral rivers flowing into the Canal now meets the standards set out by the EC Freshwater Fish Directive, to support either a cyprinid or salmonid fishery. Despite a general improving trend, the MSC and the lower reaches of the Rivers Irwell and Mersey, continue to fail to meet the required criteria to support cyprinid fisheries. This is largely due to the deep slow flowing nature of these water-bodies exacerbating the effect of consented sewage effluent and storm sewage discharges. Such conditions are responsible for promoting the accumulation of organically enriched sediments, stratification, hypoxia and high ammonia concentrations. The observed recovery of fish populations has been affected through a combination of artificial stocking programmes and natural recolonisation. The artificial stocking of coarse fish has been extensive, with over half a million fish being stocked throughout the catchment within the last two decades. Analysis of these records in conjunction with fisheries surveys, suggest that such operations are limited in their success, with frequent observations of little or no natural recruitment evident from the initial input. Poor recruitment of rheophilic species (gravel spawners) such as dace and barbel is particularly evident. Investigation into the factors (i.e. water quality or habitat degradation) limiting the success of fishes within this ecological guild will require further investigation. Although diverse habitats exist within the peripheral rivers of the catchment, access to these habitats is often denied by impassable in-stream structures, such as weirs. Spawning substrates such as gravel and macrophytes (water plants) are absent from the upper MSC and therefore the presence of fish in these areas is likely to either originate from artificial stocking or from an influx of in-drifting larvae from immediate upstream habitats. Should such habitats be made available or simulated

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where currently unavailable, notwithstanding water quality, fish production is likely to be enhanced. The return of Atlantic salmon after a 200-year absence is an excellent biological indication of the improvements in water quality over recent years. The subsequent discovery of their successful reproduction in the River Goyt in 2005 provides the first evidence that under certain environmental conditions, successful navigation of the MSC is possible for the adults of this species. Further investigation into the timing of migrations, spawning success and the survival of parr and smolts will be required in order to assess the long-term viability of a self-sustaining population of salmon in the Mersey Basin. Growth appears to be excellent for most species of coarse fish, many exceeding the expected national growth averages. Condition factors are also favourable, further indicating that food supply and the habitat requirements of the adult life stages of many species are at least adequate throughout the catchment. Conversely, the ecological requirements of dace do not appear to be fully accommodated under current environmental conditions. Despite extensive stocking efforts throughout the catchment, dace have shown little evidence of successful reproduction, with growth rates also falling below the expected national average. Sex reversal has been highlighted as a factor with potential for impacting on the health of fish populations nationally. Very high frequency of feminisation was evident in roach and perch from the upper MSC. At present these data are limited to a series of primary observations. Greater attention will need to be dedicated towards these mechanisms in order to understand the ecological significance of the process of feminisation. In general there is currently a paucity of data regarding the spawning success and recruitment of coarse fish. This is a key area for investigation, which would provide the essential data required for the effective future management of fish populations in the Mersey. The early life history of fish is a particularly vulnerable period for all species. Eggs and larval fish have greatly reduced tolerance to unfavourable environmental conditions, such as sewage fungus and low levels of dissolved oxygen. Water quality, appropriate habitat and food availability also have critical implications for the production future generations. Comprehensive surveys of spawning sites, larval fish and their diets are therefore essential, in order to identify habitat and water quality bottlenecks. Although historically abundant, the eel Anguilla anguilla and migratory (sea and river) lamprey species have failed to capitalise on the improvements in water quality and remain absent from the upper catchment. The presence of high densities of eels in the Rivers Weaver and Gowy confirm that the Mersey Estuary receives a healthy influx of elvers. Despite this, it would appear that the MSC is currently acting as a barrier to migration. Physical, physiochemical and ecological factors may all play a role in preventing recolonisation but suggest excellent potential for the experimental reintroduction of these species to the upper catchment.

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Episodic events of poor water quality have been identified as a cause and continual threat of fish kills. Storm Sewage Overflows pose a significant risk throughout the catchment, but can be particularly problematic in the lower River Irwell and MSC, where river discharge is rarely sufficient to dilute such inputs. Although stratification and hypoxic conditions prevail throughout the MSC, the largely lacustrine nature of this nutrient-rich channel also promotes the generation of algal blooms. Although not directly toxic to fish, the chemical processes driven by such blooms include extreme diel ranges in dissolved oxygen, increased alkalinity and increased toxicity of ammonia. Such conditions are believed to exist periodically during favourable conditions throughout the canal, with strong evidence of occasional fish kills. In the presence of almost limitless nutrient supplies, algal growth in the MSC can only be expected to get worse. Over 500 physical barriers, such as weirs, have been identified throughout the Mersey catchment. Not only do these restrict, or in many cases deny the passage of migratory species to spawning and rearing habitats, they also prevent the genetic mixing of coarse fish stocks and have serious implications for natural recolonisation, following localised fish kills. Weirs and lock gates have also been identified as effectively trapping fish within confined pounds of the MSC, which can have catastrophic consequences to fish, should water quality suddenly deteriorate. Recent examples of this occurred in 2006, and would be anticipated to be repeated regularly during still, hot conditions or following storm sewage discharges. In summary, despite the considerable improvements to water quality in the Mersey Basin over the past 20 years, the Manchester Ship Canal presents a major strategic barrier to the recovery and further development of coarse and salmonid fish populations within the catchment. Periodic deteriorations in water quality can be expected to cause regular fish kills, particularly with improving water clarity, as algal blooms become more frequent. These conditions, together with the physical barriers to movement and migration will also significantly constrain the development of fish populations throughout catchment and not just within the MSC itself. To conclude, substantial water quality and physical habitat challenges remain ahead. Aerial surveys conducted by APEM identified few ‘off-river’ sanctuaries, offering localise areas of oxygen rich water, within each pound of the MSC. As a consequence under the above circumstance, fish that are unable to relocate to areas of acceptable water quality will die, resulting in large-scale mortalities. Ironically, such scenarios are likely to become more common, as a general improvement in water quality is now encouraging more fish (including salmon and sea trout) to unwittingly enter these pounded zones of the canal.

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CONTENTS EXECUTIVE SUMMARY ............................................................................................i CONTENTS..................................................................................................................iv 1.0 INTRODUCTION ...................................................................................................1 2.0 OBJECTIVES OF THIS STUDY............................................................................3 3.0 A HISTORY OF FISH POPULATIONS OF THE MERSEY CATCHMENT AND THE MANCHESTER SHIP CANAL..................................................................4 4.0 RECOVERY AND OVERVIEW OF THE CURRENT STATUS OF THE FISHERY.......................................................................................................................6 4.1 Upper MSC and River Irwell Catchment.............................................................6 4.1.1 Salford Quays................................................................................................6 4.1.2 Upper Manchester Ship Canal......................................................................7 4.1.3 River Irwell ...................................................................................................9 4.2 Upper Mersey System........................................................................................14 4.2.1 River Goyt ...................................................................................................14 4.2.2 River Tame ..................................................................................................14 4.2.3 River Bollin .................................................................................................14 4.3 The Rivers Weaver and Gowy...........................................................................15 4.4 Present distribution of Species within the system..............................................16 5.0 ENVIRONMENTAL REQUIREMENTS OF FISH .............................................18 5.1 Water Quality.....................................................................................................18 5.1.1 The Freshwater Fish Directive ...................................................................18 5.1.2 Key water quality issues..............................................................................20 5.1.3 Dissolved oxygen (DO) and Biochemical oxygen demand (BOD) .............20 5.1.4 Ammonia .....................................................................................................22 5.1.5 pH................................................................................................................23 5.1.6 Eutrophication ............................................................................................23 5.1.7 Direct effects of sewage input .....................................................................23 5.1.8 Catchment summary...................................................................................24 5.1.8.1 River Irk ...............................................................................................24 5.1.8.2 River Medlock ......................................................................................24 5.1.8.3 River Irwell ..........................................................................................24 5.1.8.4 Manchester Ship Canal, Turning Basin...............................................25 5.1.8.5 Salford Quays.......................................................................................25 5.1.8.6 Manchester Ship Canal at Irlam..........................................................25 5.1.8.7 Manchester Ship Canal at Barton........................................................26 5.1.8.8 River Mersey at Flixton .......................................................................27 5.1.8.9 River Goyt ............................................................................................28 5.1.8.10 River Bollin at Heatley.......................................................................28 5.2 Habitat Requirements.........................................................................................28 5.2.1 Riverine coarse fishes .................................................................................28 (a) Early Life History.......................................................................................28

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(b) Adults..........................................................................................................29 5.2.2 Salmonids....................................................................................................32 (a) Migratory salmonids ..................................................................................32 (b) Non migratory salmonids ...........................................................................33 6.0 FISH POPULATIONS, STOCKING ACTIVITY AND EVIDENCE OF NATURAL RECRUITMENT .....................................................................................35 6.1 Lower River Irwell and upper Manchester Ship Canal .....................................35 6.2 River Irwell Upstream of Bury ..........................................................................35 6.3 River Irk .............................................................................................................37 6.4 River Medlock ...................................................................................................37 6.5 Lower River Irwell and upper MSC Fish Survey data ......................................39 6.5.1 Surveys, 1998-2000.....................................................................................39 6.5.2 Surveys, 2004-2006.....................................................................................43 6.6 Salford Quays.....................................................................................................45 6.7 Upper River Mersey...........................................................................................47 6.8 River Goyt..........................................................................................................49 6.9 River Tame.........................................................................................................50 6.10 River Bollin......................................................................................................51 6.11 Rivers Weaver and Gowy ................................................................................53 7.0 FISH HEALTH......................................................................................................54 7.1 Growth Rates .....................................................................................................54 7.2 Condition............................................................................................................55 7.2.1 Fulton’s Condition Factor .........................................................................57 7.3 Food availability ................................................................................................58 7.4 Endocrine disruption..........................................................................................60 7.4.1 Occurrence of intersex in the MSC.............................................................60 (a) Roach..........................................................................................................61 (b) Perch ..........................................................................................................61 8.0 THE RETURN OF SALMON TO THE MERSEY ..............................................64 8.1 The potential for a future salmon fishery...........................................................66 8.1.1 River Bollin .................................................................................................68 8.1.2 The River Goyt ............................................................................................71 9.0 FACTORS CURRENTLY AFFECTING THE SUCCESS OF COARSE FISH SPECIES ......................................................................................................................73 9.1 Limnophilic species ...........................................................................................73 9.1.1Oxygenated areas.........................................................................................74 9.2 Salford Quays.....................................................................................................75 9.3 Rheophilic species .............................................................................................76 10.0 FACTORS CURRENTLY AFFECTING THE SUCCESS OF MIGRATORY SPECIES ......................................................................................................................78 10.1 Catadromous species........................................................................................78 10.1.1 Eel (Anguilla Anguilla) .............................................................................78 10.1.2 Flounder (Platichthys flesus)....................................................................79 10.2 Anadromous species ........................................................................................80

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10.2.1 Atlantic salmon (Salmo salar) ..................................................................80 10.2.3 River and sea lamprey (Lampetra fluviatilis and Petromyzon marinus)..81 11.0 THE INFLUENCE OF THE MSC ON THE RECOVERY OF FISH POPULATIONS THROUGHOUT THE MERSEY BASIN ......................................83 11.1 Physical Nature of the MSC ............................................................................83 11.2 Water Quality Issues ........................................................................................83 11.3 Eutrophication..................................................................................................84 11.4 Endocrine Disruption .......................................................................................84 11.5 Physical barriers and impoundment of stocks .................................................85 11.6 Additional impacts on migration and consequences........................................85 12.0 ANALYSIS OF POTENTIAL FISH REFUGE AREAS DURING POLLUTION EVENTS USING AERIAL PHOTOGRAPHY...........................................................86 12.1 Introduction......................................................................................................86 12.2 Mode Wheel locks to Barton locks..................................................................87 12.3 Barton Locks to Irlam Locks ...........................................................................87 12.4 Irlam Locks to Latchford Locks ......................................................................89 13.0 RECOMMENDATIONS AND CURRENT KNOWLEDGE GAPS..................97 13.1 Monitoring and scientific investigation ...........................................................97 13.2 Catchment Management Recommendations..................................................100 REFERENCES ..........................................................................................................101 APPENDIX I – Water Quality Data ..........................................................................108

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1.0 INTRODUCTION The River Mersey basin has undergone dramatic change throughout the last two centuries, in terms of hydraulic structuring, ecological functioning and most significantly, water quality. This exemplifies how anthropogenic pressures have impacted negatively on our waterways, their flora and fauna and their ability to provide a sustainable resource for both abstraction and effluent demands of a growing population. Although under growing pressure from urbanisation, degraded water/habitat quality and the construction of weirs for powering industrial mills etc., it was not until the early nineteenth century that the once thriving salmon population had disappeared completely from the Mersey (Hynes, 1971). Despite the ringing of alarm bells at this time, the boom in manufacturing and associated rapid increase in population, during the onset of the industrial revolution resulted in the Mersey becoming one of the most grossly polluted river systems globally. The ecological disaster inflicted upon the Mersey was mirrored in other industrial areas of Great Britain, with parts of the Rivers Trent, Aire and Thames also classified as devoid of any fish life by the midnineteenth century (Corbett, 1907; Edwards et al., 1984; Holland & Harding, 1984). Following a series of acts of parliament to address these matters, unsuccessful attempts were made to keep pace with the growing population and associated sewage treatment demands. The failure to improve water quality resulted in many rivers still being classed as ‘fishless’ until as recently as the mid-twentieth century (Pentelow, 1955). Perhaps the most significant turning point in the history of the Mersey’s pollution took place in 1981, when the then ‘Secretary of State for the Environment’, Michael Heseltine paid visit to the Mersey Estuary (Jones, 2006). This was in response to the estuary being highlighted as one of the major detrimental factors affecting the area, following the political attention that had been drawn to Merseyside following the social unrest and outbreak of rioting in Liverpool. Indeed in a consultation paper on tackling the pollution of the Mersey catchment, published by the Department of the Environment in 1982, Lord Heseltine wrote: Today the river is an affront to the standards a civilised society should demand of its environment. Untreated sewage, pollutants, noxious discharges all contribute to water conditions and environmental standards that are perhaps the single most deplorable feature of this critical part of England. This kick-started the beginning of a concerted effort to clean up the catchment and in 1985 the ‘Mersey Basin Campaign’ was launched. This campaign was set to run over the following 25-years and established a framework for both encouragement and pressure, to ensure that the substantial financial investment for the necessary improvements to treatment of sewage and industrial effluents was obtained. These efforts, in combination with the significant decline in local chemical and heavy industry over the last two decades, have led to considerable improvements in water quality in the Mersey and its tributaries and improvements continue, with ongoing efforts to clean up discharges. As a result the Mersey system is once again capable of

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supporting fish populations, effected through a combination of gradual, natural recolonisation and periodic artificial stocking of various coarse fish species. A major highlight of the recovery process was the return of salmon to the estuary in the mid 1990s and the subsequent discovery of their successful navigation of parts of the MSC and reproduction in the River Goyt in 2005. However, despite these significant improvements, the natural sustainability of fish populations is still heavily compromised by a combination of poor water quality, habitat degradation and issues arising from the physical manipulation of the River Mersey catchment. Without doubt the biggest challenge facing the future of migratory fish populations is the 8 Km of the Manchester Ship Canal, which since its opening in 1894, has severed the link between the lower Mersey at Rixton Junction and the upper Mersey at Irlam. The canal between Irlam and the lower Irwell also poses enormous challenges to fish due to the lack of flow and the accumulation of organic pollutants and other toxins within the sediment. This combination of factors, along with the physical characteristics of the channel are responsible for the frequent anoxic nature of this stretch of water, a common cause of periodic fish kills and clearly the most significant hurdle for the continued improvement of the fishery. Nevertheless, a major development has been the establishment of a thriving coarse fish community within the enclosed area of Salford Quays, where physical mixing via “Helixor” mixers has alleviated the problems associated with stratification and the associated oxygen starvation of the lower water layers. This has improved water quality to ‘blue flag’ status and has facilitated the redevelopment of this area of previously derelict dockland with the construction of new homes, office buildings and retail and leisure facilities. Today, coarse fish communities extend from the River Irwell into the upper Ship Canal, although these populations are subject to what must be considered borderline habitat for a naturally sustainable fishery. The main aim of this review is to report the current status of fish populations within the Mersey basin, while identifying factors responsible for restricting the current and future health of both the coarse and salmonid fisheries. In particular the key aim is to identify the strategic importance of the Manchester Ship Canal in influencing the future recovery of fish populations within the Mersey Basin.

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2.0 OBJECTIVES OF THIS STUDY •

Assess the past and present status of fish stocks throughout the system, in order to understand the potential functioning of both freshwater and migratory fish populations within the Mersey catchment.

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Identify the water quality factors limiting fish populations, while summarising temporal improvements.

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Assess the factors affecting recruitment and self-sustainability of fish populations based on survey results and stocking records.

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Assess the degree of physical habitat degradation currently limiting fish populations.

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Assess the impacts of water quality on fish production, health and growth.

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Look at each of the major rivers in turn, taking into account all of the above and discuss future fish community potential.

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Assess the role of the Manchester Ship Canal in influencing the future recovery of fish stocks within the Mersey Basin.

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3.0 A HISTORY OF FISH POPULATIONS OF THE MERSEY CATCHMENT AND THE MANCHESTER SHIP CANAL Historical evidence of the biodiversity of the Mersey system prior to industrialisation is sparse, suggesting that the catchment was never relied upon to provide food on the same scale as the Rivers Great Ouse, Thames or Severn, to which many references are recorded in the literature (Jenkins, 1988; Miller & Skertchly, 1878; Wheeler, 1979). If it were not for a book concerning the history of the River Irwell published in the early part of the last century (Corbett, 1907), knowledge of the historical fish fauna of this system would be of little worth. Mr Corbett’s earliest reference to the fishery was from “The Anglers Vade Museum” published in 1680. This stated the abundance and ‘deliciousness’ of the eels in the River Irk. Corbett goes on to describe a healthy fishery within the city of Manchester, prior to the pollution of the river from ‘gas-tar’ used in the production of black paint. This was observed to completely cover the surface of the river to such an extent that the surface of the water could not be seen. Before this, coarse fish, salmon and trout were numerous and often angled for, but due to various noxious inputs, these fish along with an annual run of smelt, which used to be caught at Warrington disappeared from the river. Following the demise of the offending industry in 1824-1826 the fishery was reported to improve again, particularly above the city with chub, dace and grayling the prominent species. By the mid 1800s fishing was no longer considered worthwhile in the Irwell and, with the exception of a single salmon caught nearly dead at Warrington in 1840 it would be nearly 200 years before salmon would return to the Mersey. Although occasional small fish were observed in the upper Irwell during the late 19th century, it was thought that these must have been washed from reservoirs and would meet their certain death in river. Prior to the Irwell being regarded as ‘devoid of life’ the last fish to be recorded came from Mode Wheel Locks, when the emptying of a dry dock, in June 1907, revealed a single pike of 15 inches long and the frequent occurrence of eels (Corbett, 1907). Other records of fish in the Mersey are sparse but worthy of comment. Maitland and Campbell (1992) mention the presence of dace in the Mersey system during the 19th Century, although, within this region and at this time, the dace was regarded as a separate species and referred to as the graining Leuciscus lancastriensi. This is due to subtle differences in morphology between this population and other stocks. Also, recorded in the journal Fishing (15th May 1964), a Mr P Dumbill of Warrington reported a 38cm burbot lodged in a local museum. This fish was labelled as being taken from the River Tame by a Mr G. S. Norris in 1880 and represents the only known record of burbot from the North West (Malborough, 1970). Although unusual, this is a highly significant record as burbot are thought to have suffered extinction from the British Isles in the early 1970s as a result of a combination of both poor water quality and habitat degradation, with the last specimen being caught in the Great Ouse system in 1972. From these records we know that the Mersey once supported a healthy population of salmon and eels, demonstrating that the river was once clean and without physical constraints to the passage of fish between the estuary and the upper tributaries. It is therefore a fair assumption that the rivers of the Mersey catchment, historically would

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have supported a fishery with a typical longitudinal zonation of species diversity in accordance with the model of Huet (1959). This is summarised as:

1. Trout (Salmo trutta) Zone. Cool, steep, fast flowing, well oxygenated brooks and streams. The substrate will mainly consist of rocks, boulders and pebbles, with some gravel and sand. (Likely common species also include: salmon Salmo salar, bullhead Cottus gobio and stone loach Barbatula barbatula) 2. Grayling (Thymallus thymallus) Zone. Associated with larger rivers and streams. Flow is still fast and the water well oxygenated. Pools are interspersed between riffles. The substrate will be mixed but mainly comprise gravel. (Likely common species also include: trout Salmo trutta, salmon Salmo salar, bullhead Cottus gobio and stone loach Barbatula barbatula, dace Leuciscus leuciscus and minnow Phoxinus phoxinus) 3. Barbel (Barbus barbus) Zone. Moderate current with increasing depth and areas of slack flow. Banks may be alternately erosional and depositional. (Likely common species also include: trout Salmo trutta, salmon Salmo salar, bullhead Cottus gobio, stone loach Barbatula barbatula, dace Leuciscus leuciscus, minnow Phoxinus phoxinus, gudgeon Gobio gobio, chub Leuciscus cephalus and grayling Thymallus thymallus) 4. Bream (Abramis brama) Zone. Quiet lowland waters, including canals. Flow is slow and summer temperatures will be high and DO levels low. Waters will be turbid and deep. The substrate will be dominated by fine silt sediment. (Likely common species also include: chub Leuciscus cephalus, roach Rutilus rutilus, rudd Scardinius erythrophthalmus, carp Cyprinus carpio, silver bream Abramis bjoerkna, tench Tinca tinca, perch Perca fluviatilis, three-spined stickleback Gasterosteus aculeatus and pike Esox lucius). Based on both historical and present day records of the fishes of the Mersey Estuary (Wilson et al., 1988), prior to the catchment being polluted, the species listed above are known to have been complimented with migratory species such as eels Anguilla anguilla, river lamprey Petromyzon fluviatilis, smelt Osmerus eperlanus and flounder Platichthys flesus.

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4.0 RECOVERY AND OVERVIEW OF THE CURRENT STATUS OF THE FISHERY 4.1 Upper MSC and River Irwell Catchment 4.1.1 Salford Quays Following the isolation of two basins (7 & 8) of Salford Quays in 1986 with a third basin (9) being enclosed from connection with the MSC in 1989, water quality was closely monitored prior to the activation of “Helixor” mixers in August 1987 and October 1989 respectively (Bellinger et al., 1993) (Figure 4.1.1). Dramatic changes in water quality were quickly realised with significant reductions in Ammonia and turbidity and increases in DO and Chlorophyll a. An initial fish survey revealed that small wild populations of roach and sticklebacks were already present (Hendry et al., 1988), and were believed to have originated from either the upper Irwell or the Bridgewater Canal prior to their entrapment within the Quays. Back-calculated lengths and historical growth analysis of the roach revealed that these fish originated from a stunted population, where their growth had previously been suppressed by environmental stressors. However, their growth rate had since rapidly increased in consequence of the observed improvements in water quality within the enclosed basins (Hendry et al., 1997).

Figure 4.1.1: Basins of Salford Quays In response to these encouraging observations, a research programme was initiated to investigate the recreational fishery potential of the Quays. The following analysis of water quality demonstrated that, with the exception of levels of lead, zinc and unionised ammonia (NH3) the Quays were able to meet all other criteria for supporting a

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coarse fishery as defined in the ‘European Freshwater Fish Directive’, with many criteria relating to salmonid species also being met. Following careful consideration regarding a balanced community structure and stocking density, an initial introduction of fish took place in August 1988 (APEM, 1989. The species included roach, beam, carp and rudd and a total of 631 individuals were introduced to a confined yet representative area of the Quays (basin 7c) as the basis for an experimental monitoring programme, investigating fish growth, health, survival and feeding over an entire growing season. In addition, the unstocked areas provided a control that allowed monitoring of the effects of fish-stocking on various water quality parameters. Despite occasional deteriorations, water quality has remained within recommended guidelines most of the time, with no water quality deteriorations being attributable to the presence of fish. Most species performed well in terms of growth and condition. Bream were the only exception, with some individuals showing symptoms of stress and ulceration as well as a degree of mortality, although as a whole the population showed growth in both length and weight. Following the success of the initial stocking experiment, water quality had improved to such an extent by 1989 that 12,000 coarse fish were introduced into the 20 acres of enclosed waters (APEM, 1991). Growth rates observed since stocking have indicated that the Quays have supported some of the fastest growing coarse fish in the UK (Hendry et al., 1997). Over the last two decades, Salford Quays have supported a healthy mixed fishery and, despite a lack of natural habitat heterogenity, the provision of artificial structures have facilitated natural reproduction and subsequent recruitment of some species (Hendry et al., 1994). The dramatic ecological improvements made in this area offer encouragement for further improvements to be made within the upper reaches of the MSC. 4.1.2 Upper Manchester Ship Canal As recently as the early 1990’s only roach and stickleback were to be found in the upper MSC (Hendry, 1991) (location of the upper MSC shown in Figure 4.1.2). At this time, the water was only capable of supporting fish life during the colder months as anoxic conditions often prevailed during summer, causing the generation of sediment mats, excessive bubbling from gas production and associated foul odours.

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Figure 4.1.2: Location of the Upper MSC Following the improvements to water quality within the enclosed Quays, efforts were made to improve the aesthetic problems of the adjacent canal. Following a detailed research and experimented program, an oxygen injection programme was initiated in 2001. This achieved the desired objective of preventing dissolved oxygen at the bed level from falling below 4 mg/L, thus greatly reducing the problems previously experienced (Wilson et al., 2000). In addition to the aesthetic benefits of this project (i.e. the prevention of excessive bubbling and odours), dramatic ecological improvements have also been observed. There has been a highly significant increase in the number of macroinvertebrate species being recorded in the oxygenated area of the Turning Basin. Thirty nine species in total have now been recorded from this area which compares to only four (pollution tolerant) species recorded from the Pomona Dock area, which, only a little further upstream, acts as a useful control site, lacking oxygen supplementation (Site locations are displayed in Figure 4.1.2b).

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Figure 4.1.2b: Location of invertebrate monitoring sites and oxygenation units Fish populations are also now able to colonise the Turning Basin throughout the year, capitalising on the increased abundance of invertebrates and maintaining higher than average growth rates and condition factor. Previously during the summer months, these fish would have had to undertake upstream migrations towards the lower River Irwell in order to avoid asphyxia. With gradual improvements in the water quality of rivers feeding the upper MSC over the last few years, encouraging natural colonisation from the upstream tributaries and the Environment Agency’s restocking programme of the River Irwell, 6 species (Table 4.1) are now present in the upper reaches of the Ship Canal. However, despite recent improvements in water quality over the last few years, the MSC remains a borderline habitat for fish populations. Episodic pollution and major habitat limitations (such as spawning habitat, nursery areas and food resources for the early stages in particular) still restrict the potential of populations to be self-sustaining in the longer term. 4.1.3 River Irwell Rising from Rossendale Fell in the Northwest Pennines the River Irwell flows south towards Bury before being joined by the River Roche and winding its course through the cities of Salford and Manchester (Figure 4.1.3). Historically the River would have continued to meander westward towards its confluence with the natural course of the River Mersey allowing the passage of salmon, which once graced the river. Today the river terminates its natural course at Blackfriars Bridge on entering the upper MSC (Figure 4.1.3b).

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Figure 4.1.3: Map of Irwell catchment Today the River Irwell’s banks are modified throughout much of its length for flood control, with flows also extensively modified by historically constructed weirs. On entering Manchester the river becomes canalised, approximately 3 km upstream of the first lock on the MSC at Mode Wheel (Figure 4.1.3c).

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Figure 4.1.3b: Map of the River Irwell entering the MSC

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Figure 4.1.3c: Images of a canalised section of the River Irwell as it enters the MSC close to Blackfriars Bridge A study of the lower River Irwell in 1990 (Adelphi Weir to Blackfriars Bridge) showed that the river was still grossly polluted at the time. However, the last 25 years have seen dramatic improvements (APEM, 2007). The canalised sub section of the lower Irwell (Victoria Station to Blackfiars Bridge) is still subject to the effects of a wide range of historical pollutants which lie within the bed substrate. In particular, high organic loads in the sediment have led to elevated BOD levels and consequently, the lower river is often subjected to depleted DO concentrations. However, as a result of a general decline in industry, improvements in sewage treatment and investment in combined sewer overflows (Harper, 2000), long term water quality improvements are now evident. An increase in macroinvertebrate biodiversity and decreasing overall BOD levels are good indications of such improvements. Never the less, the River Irwell is still subjected to frequent episodic pollution events from storm sewage overflows and in 1997 this stretch of water was still classified under the Chemical General Assessment scheme, as ‘poor’ (Environment Agency, 1997). Habitat degradation is also a major feature, particularly in the lower reaches of the Irwell, with little macrophyte growth throughout the majority of this section, seriously limiting the scope for successful spawning in this area. The Wilburn Street Basin area offers some of the only macrophytes for spawning and is the only remaining ‘off river’ habitat, where larval and juvenile fish can seek sanctuary from floods, thus providing a unique and essential nursery habitat (Figure 4.1.3d). Further upstream, greater heterogeneity in terms of habitat increases opportunities for natural recruitment, although successful incubation of eggs and subsequent survival of larvae is seriously compromised by both physical habitat and water quality parameters. The 12 Final Report – September 2007

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upstream passage of coarse fish beyond Adelphi Weir is not possible and therefore limits the spawning habitat available to rheophilic species such as dace and chub.

Figure 4.1.3d: Location and image of Wilburn Street Basin Although natural populations of brown trout are present in the upper reaches of the Irwell, the diversity of the fishery in the lower river relies heavily on artificial stocking and like the MSC, should still be considered as a borderline habitat for fish populations. Species known to be present in the lower Irwell, include roach, chub, dace, tench, bream, carp, rudd, gudgeon, bullhead, stickleback, trout, pike and perch. Another major consideration for the future development of fish populations in the Irwell (both upper and lower) is the heavily modified channel structure of the lower Irwell and MSC. The morphology of the water body changes dramatically as water passes from the lower Irwell towards the Turning Basin, with deep water and reduced water velocities resulting in substantial water quality problems, which are likely to remain in this section. However, perhaps of greater significance is the influence of the MSC downstream of the Turning Basin. The many locks along this stretch of the Canal present barriers which seriously compromise the passage of migratory fish. This represents a substantial impediment to the future development/recovery of fish populations in the Irwell, as the river remains isolated from its estuary.

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4.2 Upper Mersey System 4.2.1 River Goyt The River Goyt begins its course on the Derbyshire moors between Buxton and Macclesfield and feeds Errwood and Fernilee reservoirs before making its way to Stockport where it meets the River Tame and becomes the Mersey. In the upper reaches the Goyt supports a thriving brown trout fishery, with good quality spawning habitat available in the many tributary streams. Below the reservoirs the Goyt benefits from compensation discharge from Fernilee reservoir, which maintains a healthy flow, supporting a mixed salmonid and coarse fishery. In the lower reaches, between Marple and Stockport the river is regarded as a good quality coarse fishery, with an abundance of large chub and barbel. Other species known to be present from EA fish surveys include perch, pike, roach gudgeon and grayling. Despite the occurrence of some juvenile fish it appears that there may be factors limiting natural recruitment, with the fisheries reputation relying heavily on stocking practices. Undoubtedly the most significant discovery on the River Goyt and indeed the entire system, was the capture of four 0+ salmon parr near Stockport during 2005. For the first time since the industrial revolution, this proves the potential of the Mersey system to support migratory fish stocks once again. Major factors affecting the natural recruitment fish stocks on the River Goyt include obstructions to the migration of coarse and salmonid fish. Many in-stream structures have been identified as being impassable under low flow conditions, 15 of which were regarded as totally impassable barriers (APEM, 2006). The siltation of spawning gravels used by salmonids, grayling and rheophilic cyprinids, such as barbel and chub, has also been highlighted as a limiting variable, with much potential spawning habitat regarded as being unsuitable due to high ‘fines’ content and/or a covering of algae. 4.2.2 River Tame The Tame is fed from a combination of reservoirs situated in the Pennines near Denshaw, before making its way south to the confluence with the River Goyt where the two rivers join to become the River Mersey. Like the River Goyt, the Tame supports a healthy, self-sustaining population of brown trout in the upper reaches, with the species composition becoming dominated by coarse fish as the river flows south towards Stockport and the confluence with the River Goyt. Barriers to migration are also present on the River Tame, with the substantial Weir at Etherow Country Park presenting a major obstruction to the passage of fish. In addition to brown trout, the Tame is known to support chub, gudgeon, minnow, stone loach, dace pike roach, perch and bullhead. 4.2.3 River Bollin Rising within Macclesfield Forest the River Bollin flows west, passing through Trentabank, Ridgegate and Bottoms Reservoirs towards Macclesfield. From there it follows a northwesterly course passing through the towns of Prestbury and Wilmslow to Bollin Point, a distance of approximately 52km. At Bollin Point the river would

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have historically joined the River Mersey, but today its course is briefly interrupted, as it first has to flow across the MSC. The River Bollin supports a mixed coarse fishery and has been identified as being capable of supporting Atlantic salmon, which have been observed attempting to access the lower River by jumping Heatley Weir. Unfortunately, the river upstream of Heatley Mill presents a further eleven barriers to migration, which currently prevent the passage of salmon to the mid and upper Bollin as well as the River Dean. This is a tributary of the River Bollin, which has been highlighted as providing both a high quality and quantity of spawning and rearing habitat for salmon. The River Dean is therefore considered to have been historically an important spawning tributary and indeed may be so again in the future. Hence the tributaries may be significant not just for the Bollin sub-catchment but also from a whole Mersey catchment perspective.

4.3 The Rivers Weaver and Gowy The Rivers Weaver and Gowy have been incorporated into this review for comparative purposes. Because of their more direct connectivity with the Mersey Estuary, they benefit from additional migratory species such as eel and river lamprey. A direct comparison of fish community structure and water quality between these rivers and the upper Mersey catchment should therefore elucidate whether water quality of the Upper Mersey is restricting the colonisation of these migrants, or whether the MSC is acting as a barrier to migration.

Figure 4.3: Map showing the location of the Rivers Gowy and Weaver confluence with the River Mersey

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4.4 Present distribution of Species within the system Due to extensive stocking over much of the catchment in the last 15 years, the presence of a species in its adult life stage is not necessarily an indication that that species is able to reproduce successfully and maintain a naturally sustainable population. This may be due to a number of factors including a lack of suitable spawning habitat, constraints on movement and migration, the susceptibility during early development stages to the lethal effects of toxins or a lack of a specific food resources required at various life stages. However a comprehensive list of all species caught in each area of the catchment does provide a useful baseline on which to investigate the factors that may be constraining establishment success on a species by species basis. Table 4.1 is based on electric fishing, netting, and screen intake surveys, as well as angling records, and lists all species that have been recorded from each area of the catchment since the fish population began its recovery in the late 1980s.

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Table 4.1 Current species summary for the River Mersey catchment.

•

• • •

•

•

•

•

•

•

•

• •

• •

•

• •

• • •

• • •

• • •

•

•

•

•

•

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• • • • •

• •

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Lower MSC •

• • •

• • •

• • •

• • • •

•

• •

• •

• •

•

•

•

• •

• • •

•

• • •

R. Bollin

• •

River Gowy

•

•

• • • •

R. Weaver

•

• •

• • • • •

Lower R. Mersey

•

• • •

Upper R Mersey

•

R. Goyt

• • • • • • •

Upper MSC

Salford Quays

• •

• • •

R. Tame

• • • • • • • •

R. Medlock

Roach Dace Chub Tench C. bream C. carp Rudd Gudgeon Barbel Minnow Crucian carp Roach x Bream hybrid Stone loach Bullhead 3-spined stickleback Trout Sea trout Salmon Grayling Pike Perch Ruffe Eel River lamprey Brook lamprey Flounder

R. Irk

R. Irwell

Species

• • •

• • •

•

•

•

•

•

•

• •

• •

•

•

• •

• • • •

• • • • • •

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5.0 ENVIRONMENTAL REQUIREMENTS OF FISH 5.1 Water Quality

5.1.1 The Freshwater Fish Directive In 1978, the EC Freshwater Fish Directive (EC FFD) was brought into effect, in order to ensure that all European freshwaters (rivers, lakes and reservoirs) designated as fisheries, maintain a standard of water quality suitable to support healthy fish populations. This means that water quality has to be sufficient to sustain a species throughout all life stages, enabling successful reproduction and maintenance of a population. In order to allow migration and genetic mixing, it is also vital to ensure that spatial water quality parameters do not act as a barrier to fish movement, both between the sea and rivers, between the rivers of the catchment and indeed between reaches of the same river. Because of the variable water quality demands of different families of fish, the directive sets out two categories of water quality targets, to meet the demands of both salmonids and cyprinids. Salmonids such as salmon and trout, typically demand high water quality, higher flows and high dissolved oxygen levels, while cyprinids and other coarse fish are less demanding, typically occupying lowland habitats, with reduced velocities and higher nutrient values with a capacity to adapt to lower oxygen levels. It must be noted at this point that the EC FFD only regulates water quality parameters and does not take account of the physical habitat demands of individual species. Although physical habitat is less important to the survival of adult fishes, availability of suitable physical habitat is of critical importance to egg, larval and juvenile stages of development. Detailed knowledge of a species habitat and dietary requirements and environmental tolerance limits are therefore fundamental to understanding the factors that influence recruitment success (Houde, 1994). This section deals with water quality whereas the physical habitat requirements of freshwater fishes will be addressed in the following section. Target criteria within both the salmonid and cyprinid fishery categories are further divided into Imperative (I) and Guideline (G) values. While Imperative values (Table 5.1) must be met for the fishery to achieve compliance, ‘Guideline’ values (Table 5.2) are desirable quality standards that should be achieved where possible. In exceptional circumstances, such as storms or droughts, derogations (waivers) may be granted for certain substances and the required standards may be exceeded without the stretch failing to comply.

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Table 5.1 Imperative Standards set out by the ECFFD IMPERATIVE PARAMETER NOTES STANDARDS Units Salmonid Cyprinid Temperature °C 1.5 3.0 Increase due to thermal discharge °C 21.5 28.0 Maximum at monitoring site °C 10.0 10.0 Maximum for breeding season Dissolved mg/l 50% >9 50% >7 oxygen PH 6 to 9 6 to 9 Phenols - No odour No odour Hydrocarbon Non Non oil visible visible Non-ionised mg/l 0.025 0.025 ammonia Total mg/l 1.0 1.0 ammonium Total residual mg/l 0.005 0.005 chlorine Total zinc mg/l 0.03 0.3 Hardness 100 milligrammes CaCO3/ litre

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Table 5.2 Guideline Standards set out by the ECFFD GUIDELINE PARAMETER NOTES STANDARDS Units Salmonid Cyprinid mg/l 50% >9 50% >8 Dissolved oxygen 100% 100%>7 >5 Suspended solids mg/l 25 25 BOD mg/l 3 6 Nitrites mg/l 0.01 0.03 Non-ionised mg/l 0.005 0.005 ammonia Total ammonium mg/l 0.04 0.2 Hardness 100 milligrammes mg/l 0.112 0.112 CaCO3 /litre 5.1.2 Key water quality issues Although not within the scope of the current review paper, a detailed review of the water quality of the MSC has been carried out as a parallel study by APEM (APEM, 2007). The water quality report highlights the main water quality criteria currently failing to meet EC FFD standards within the MSC (i.e. oxygen and ammonia), with further concern over BOD, pH and suspended solids. The impacts of these criteria and the intrinsic relationships between some of these water quality parameters are summarised below. 5.1.3 Dissolved oxygen (DO) and Biochemical oxygen demand (BOD) The physical structure of the upper MSC can be described as a vertical sided flume, with depth ranging from 5-9 metres and consequently, no or very little discernable flow or natural mixing. For many years this waterway served its purpose of providing a direct navigation route between the Irish Sea and Manchester, before the tailing off of shipping traffic in the 1970s. The combination of a legacy of long term organic input to the Irwell system and the physical characteristics of the MSC have led to over a centuries worth of accumulated pollution being deposited within the upper reaches of the canal, which, lacking suitable flow to transport suspended particulate and soluble fluxes to the estuary, has essentially functioned as a settlement basin for a heavily industrialised and highly populated catchment basin upstream. In the upper reaches of the canal, approximately 0.5m of new of new sediments are deposited each year as a result of the operation of storm sewage overflows (Hydraulic Research Centre, 1981)

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Such levels of organic pollution within the bed sediments induce enormous stress on the aquatic environment due to high levels of oxygen consumption by the substrate, that at times can completely deplete the overlying water of available dissolved oxygen (anoxia). This is particularly problematic to aquatic life during the summer months when the combined lack of significant flow and poor mixing make this waterbody prone to stratification for extended periods (Hendry et al., 1993). Tolerance to anoxia Hypoxia has been identified as an important environmental stressor affecting many physiological processes in fish (Braun et al., 2006). The FFD requirements are to maintain 50 percentile DO levels above 7 mg/L for cyprinids and 9 mg/L for salmonids and thus recognise the higher tolerance levels of the Cyprinidae to hypoxia. Research has demonstrated that cyprinids such as carp have evolved adaptive mechanisms in order to cope with hypoxia (Zhou et al., 2000) and may be capable of withstanding DO levels as low as 0.5 mg/L for limited periods. This is achieved by reducing energy metabolism while enhancing the supply of oxygen from anaerobic sources (Dunn & Hochachka, 1986), or in the case of goldfish Carassius auratus, by an ability to regulate gill morphology to cope with such conditions (Sollid et al., 2003). It must be noted that such experimental observations have isolated DO from other parameters, which may be intrinsically linked to such conditions in nature, that may also be harmful to fish. The recent return of adult salmon to the Mersey and their successful reproduction in the River Goyt raises the question: would Mersey parr survive the physiological stresses of smoltification under the observed water quality conditions and be able to tolerate the navigation of the MSC on their seaward journey? This is clearly an important area for experimental investigation, but laboratory experiments conducted by Alabaster et al. (1979) suggest that smolts may be capable of tolerating DO levels as low as 3 mg/L for limited periods in freshwater. Although 50 percentile FFD targets for DO need to be met in order to ensure better fishery potential, such observations indicate that short term episodic events of DO below these levels may be tolerated by the adult life stages of some species, particularly if oxygen supplemented havens were available at intervals along the canal, since fish have been shown to exhibit behavioural responses that enable them to take advantage of zones of higher oxygen concentration. Stratified gradients of oxygen levels have been shown to be an important factor in determining the vertical distribution of fishes (Burleson et al., 2001). Many studies have shown that, where oxygen gradients exist either laterally or vertically, fish are able to sense preferred oxygen levels and relocate to these area. Experimentally, brook trout (Spoor, 1990) and largemouth bass (Burleson et al., 2001) have been shown to actively select zones of preferred DO levels. Field observations have also shown that different species of fish distribute themselves differentially throughout the water column where a thermocline exists, with roach and pelagic fishes occupying surface waters richer in oxygen (Hendry et al., 1988). Further work by Hendry et al also reported the limited time that fish could tolerate the lower anoxic layers and demonstrated that fish were moving in and out of the anoxic zone to take advantage of

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benthic dietary items, but when captured in fyke nets at these lower levels, survival times were limited. The ability of fishes to relocate to areas where oxygen levels are preferable has been reported to shift the focus of trophic interactions. One example would be adult fishes being forced to occupy the surface layers in order to avoid asphyxiation. This shifts the focus of diet from benthic (bottom) invertebrates to littoral fauna (marginal), which can affect the predation and mortality of larval fishes, occupying these zones (Breitburg et al.,1999). Lateral oxygen gradients also exist on the MSC with the Daveyhulme effluent reported as an oxygen sanctuary during times of poor water quality. Again it is possible that this effective ‘herding’ of fish into confined areas could shift trophic focus, thus impacting on the recruitment of larvae. 5.1.4 Ammonia Principle sources of ammonia in freshwater originate from domestic sewage effluent and agricultural run-off (Alabaster, & Lloyd, 1982). Although excessive levels of ammonia can cause direct damage to the gill epithelium, in lower concentrations it may cause general tissue damage to both internal and external organs. Toxicity is dependant upon the concentration of un-ionised ammonia (NH3) present in solution, with both temperature and pH, playing an important role in influencing these concentrations (Nash et al., 2003). Un-ionised ammonia is many times more toxic than the ionised form. The relationship between ionised ammonium (NH4+) and unionised ammonia is expressed as (Hellawell, 1989): NH4+ + OH- ↔ NH3 + H20 High temperature and pH shift the equilibrium to the right, where un-ionised ammonia predominates. In waterbodies receiving high levels of ammonia, toxicity is likely to be greater during warm weather, when phytoplankton blooms result in elevated pH levels via consumption of CO2 during photosynthesis. These are the same conditions that prompt stratification, thermocline formation and low bottom water oxygen concentrations. Hence, exposure to toxic levels of ammonia is therefore likely to be a cumulative ‘stressor’ becoming more problematic in accordance with hypoxic conditions. Fish kills in carp ponds have shown that mortality occurs at approximately 0.5 mg/L of un-ionised ammonia at DO levels around 6 mg/L (Alabaster, 1982). However at lower DO levels of 2 mg/L, lethal ammonia levels of 0.2 mg/L have been recorded. The European Freshwater Fish Directive (ECFFD) sets an imperative maximum value of 0.025 mg/L of un-ionised ammonia and 1 mg/L for total ammonium for compliance. However, where aquatic ecosystems are under excessive stress from hypoxic conditions, these standard values may not be sufficient to prevent damage to fish communities and therefore the ECFFD suggests a guideline standard of 0.005 mg/L for NH3 and 0.04 and 0.2 mg/L for total ammonium for salmonids and cyprinids respectively.

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5.1.5 pH Although pH levels largely remain within the recommended limits for cyprinid and salmonid fishes, the occurrence of phytoplankton blooms as a result of eutrophication, greatly increase the risk of the lower River Irwell and MSC experiencing pH levels exceeding the upper target limit of 9 in the future. pH values exceeding 9 have been shown to effect the growth of most fish populations by interfering with normal ionic regulation. While decreasing pH levels are known to increase the toxicity of a variety of pollutants (e.g. many trace metals, such as copper and aluminium), elevated levels of pH increase the toxicity of ammonia to fish, by increasing the proportion of unionised ammonia. Elevated pH may occur as a consequence of photosynthesis by algal blooms utilising CO2. 5.1.6 Eutrophication The most prominent issue surrounding eutrophication is excessive algal growth. This in turn gives rise to elevated pH and causes extreme temporal dissolved oxygen gradients in the epilimnon. In addition to the negative effects of low DO, super saturation, which occurs during the hours of daylight, has been reported to cause gas bubbling which has been observed to kill Coregonid larvae in the surface layers (Stadelmann, 1984). Because of its function in limiting the production of algae, phosphorus is usually identified as the main focus in regulating the eutrophication process (Cooke et al., 1993). The combined treated sewage effluent points which discharge into the River Irwell currently contribute 89% of the orthophosphate load being delivered to the upper MSC (Environment Agency, 2002b). The predicted standards are still ten times higher than required to comply with the UWWTD and expert opinion suggests that 15-20 µg/l is the maximum permissible concentration to remove the risk of algal blooms. However, the MSC is thought to be phosphate saturated and any effort to reduce discharge levels at point source will be replaced by dissolution from phosphate rich bottom sediments (Envirionment Agency, 2002b). Whilst it is not known whether oxygen injection in the MSC has prevented P release from the sediments, maintaining bottom DO by artificial mixing within the Quays has achieved remarkable success in locking up sediment derived P and hence controlling algal blooms. 5.1.7 Direct effects of sewage input Not only does sewage input into the system play an important role in maintaining the amount or suspended solids, which currently limit water transparency and the production of algae, but also has a range of other effects on fish populations. Although sewage discharges can offer highly nutritious feeding opportunities for adult fishes, overexposure to such pollutants can result in rapid mortality. Where fish are not able to move in and out of such areas, such as being retained in anglers keep-nets, then mortalities are likely to occur (personal obs.). Where such effluents give rise to saprophytic microbial growths, more serious detrimental effects are likely to be observed for the survival and growth of embryonic and larval stages of fish (Fraser & Clark, 1984). The filamentous growths of Sphaerotilus produce a slime growth in organically polluted waters (sewage fungus). This initially causes the degradation of

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spawning habitats by clogging bottom sediments and depleting ‘local’ oxygen levels. The growth of such filaments on the chorion of fish eggs can kill embryos during development by either limiting available DO and increasing levels of CO2 in the microclimate of the embryos, or by physically preventing embryos emerging from the egg. Larvae are also susceptible to the effects of sewage fungus with the gills of young larvae susceptible to becoming clogged with bacterial filaments, thus impairing respiration (Fraser & Clark, 1984). Where such bacterial growths are prolific, the successful incubation of eggs is seriously compromised. In addition the detrimental effects to early development stages, the occurrence of intersex is also associated with sewage effluent discharges, with the incidence and severity of feminisation being positively correlated with the proportion of treated sewage effluent in receiving waters (Gross-Sorokin et al., 2006). 5.1.8 Catchment summary The Water Quality review (APEM Report, 2007) limits its focus to the MSC only, but to understand the factors limiting the recovery of fish populations throughout the Mersey Basin, it has been necessary to consider the water quality issues if the tributary rivers such as the Irwell, Mersey and Bollin. In general, the long term trend is that of significant improvement throughout the catchment. The peripheral rivers benefit from more turbulent flows and are therefore not subjected to the same stresses as the MSC, such as prolonged hypoxia, algal population retention and elevated pH. However, sporadic events, principally from combined sewer overflows can at times seriously compromise water quality and the well being of fish populations. Here we summarise the historical and present water quality issues of several areas of the MSC and tributary rivers, with summary graphs provided for each part of the catchment in Appendix I. For a detailed appraisal of water quality in the MSC, direct reference should be made to the parallel water quality review (APEM Report 410039). 5.1.8.1 River Irk Dramatic improvements have been observed in the River Irk since the late 1970s. Despite sporadic peaks in BOD, monthly mean values of DO during 2005-2006 have all met the target values to maintain a salmonid fishery. Total ammonia also shows a dramatic long term reduction, with current levels rarely exceeding the EC FFD target for cyprinids. 5.1.8.2 River Medlock Improvements in the River Medlock mirror those observed in the River Irk. Despite occasional peaks in BOD, current monthly means for DO and ammonia have all met the imperative targets to maintain a salmonid fishery. 5.1.8.3 River Irwell Benefiting from those improvements already highlighted in the tributary rivers, the River Irwell continues the trend in improvements of the upper catchment. Temporal reductions in Sewage Treatment Discharges since the late 1970s, have resulted in a dramatic reduction in BOD, with a concomitant increase in levels of DO. Although,

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target values have been met for most months during 2005-2006, sporadic peaks in BOD have occurred and DO has also failed to reach the target levels for a cyprinid fishery in some months. Failure of DO standards is likely to be influenced by the physical nature of the lower Irwell, where the deep nature of this water body lends itself to regular periods of stratification and hypoxic conditions. Although the long term trend in ammonia levels shows a dramatic reduction, monthly means over 20052006 have rarely met EC FFD targets, with monthly mean values reaching seven times higher than target values. 5.1.8.4 Manchester Ship Canal, Turning Basin The Turning Basin of the MSC (approximately 1.5 Km in length) has been included in this review in order to compare an area of the MSC that benefits from an amelioration measure, with those areas more typical of the MSC (i.e. the remaining 20km of the fresh water canal). The Turning Basin has benefited from oxygen supplementation since 2001 and has since indicated significant improvement in biological status, with the colonisation of pollution sensitive invertebrate species and the presence of fish communities throughout the year. The graphs in Appendix I (Fig. A13 a & b), clearly show that since the initiation of the oxygen programme, annual mean BOD has remained for the first time since 1987 within EC FFD target levels. With the exception of one month during 2005-2006, monthly means have also been comfortably within the required standards. Annual DO levels also began to achieve these standards as from 2001 with monthly means generally being maintained at target levels to maintain a salmonid fishery (Fig. A14 a & b). Unfortunately no data are available regarding ammonia concentrations within this section of the Canal. 5.1.8.5 Salford Quays Since their isolation from the MSC in 1986, the Quays have continued to improve in water quality. Annual means of B.O.D have shown a general trend in reducing and now average approximately 50% of the values observed in 1989. Monthly means during 2005-2006 are now well within the target values for cyprinids and in most cases also satisfy the criteria for salmonids. The operation of ‘Helixor’ mixers has maintained stable annual levels of dissolved oxygen with monthly means over 20052006 also meeting the targets for salmonids. Despite a lack of any input of sewage effluent since their isolation, annual mean values for total ammonia continue to border on the target values, with monthly values often well in excess of EC FFD requirements for cyprinid fishes. 5.1.8.6 Manchester Ship Canal at Irlam In the absence of oxygen injection, the MSC continues to fail to meet the EC FFD standards required for a cyprinid fishery. Despite BOD targets being met in the majority of months at Irlam during 2005-2006, monthly mean levels of DO failed to meet the required standards. During summer months mean monthly values dropped to approximately 15 % of the target values and typically failing the 100% compliance level of 5 mg/l (Fig. A16).

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5.1.8.7 Manchester Ship Canal at Barton Barton 2006 monthly D.O. (mg/l) +/- Minimum and Maximum Values 35

100% compliance required for EC FFD guideline level

30

50% compliance required for EC FFD imperative level

D.O. (mg/l)

25

50% compliance required for EC FFD guideline level

20

15

10

5

0 J

F

M

A

M

J

J

A

S

O

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D

Figure 5.1a The MSC at Barton was selected as being typically representative of the canal and due to the availability of continuous (15 minute) data logs collected using a ‘Data-sonde’ logger. This has facilitated the examination of DO data at a much higher temporal resolution. It was expected that where wide ranges of minimum and maximum DO values occurred (Fig 5.1a), that this would be due to diel fluctuations due to algal biomass. On analysis of these data, it appears that although diel ranges are of great importance due to the water quality issues directly linked to algal blooms, where algal production is limited, hypoxia is often maintained for extended periods of time, sometimes lasting as long as several weeks (Fig 5.1c). These extended periods may be due to die back of algal blooms or still weather conditions which result in poor vertical mixing. Alternatively, oxygen sags may follow storm derived pollution events. Regardless of how these events originate, this high-resolution analysis of DO concentrations confirms that fish populations are likely to be severely compromised by such conditions.

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APEM Scientific Report - 410039 % of hourly DO mg/L during each month in excess of Fisheries Directive trargets during 2006 at Barton on the MSC % > 5 mg/L

100

> 5 mg/L target

90 % > 7 mg/L

80 % > 9 mg/L

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> 7 mg/L target for cyprinids & > 9 mg/L target for salmonids

60 50 40 30 20 10

Dec

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Figure 5.1b Continous (hourly) DO mg/L at Barton April and October 2006 30 DO mg/L

25 50% cyprinid target DO (mg/L)

20 50% salmonid target

15 10 5

28/10/2006

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30/09/2006

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27/05/2006

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01/04/2006

0

Figure 5.1c 5.1.8.8 River Mersey at Flixton In accordance with the rest of the catchment, the Mersey at Flixton has demonstrated a gradual decline in annual mean levels of BOD and ammonia, indicating a reduction in organic sewage inputs. Despite these reductions, long-term DO levels show little change, with annual mean values having been relatively stable since the late 1970s. Despite annual mean DO levels exceeding EC FFD standards for salmonids in recent years, monthly values vary considerably, with the target values for cyprinid fish rarely

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being met between the months of June and August. The current status of the River Mersey at Flixton does not currently conform to the EC FFD requirements of a coarse fishery, with BOD, DO and ammonia levels all falling short of targets during some months. 5.1.8.9 River Goyt Long-term data have not been available to establish temporal improvements in the water quality of the River Goyt. However, current water quality standards for BOD, DO and ammonia indicate that the Goyt fulfils the EC FFD requirements of a salmonid fishery. 5.1.8.10 River Bollin at Heatley The River Bollin at Heatley has shown dramatic improvements in water quality since the late 1970s. Reductions in levels of BOD and ammonia indicate a significant reduction in sewage effluent inputs over the last three decades and the River currently meets the required water quality standards for BOD, DO and Total ammonia to support a salmonid fishery.

5.2 Habitat Requirements 5.2.1 Riverine coarse fishes (a) Early Life History Analysis of population structure of riverine fish species often demonstrates a wide variation in recruitment success between years. There is much evidence to suggest that the bottlenecks to recruitment in many fish populations relate principally to spawning success and the growth and survival rates of newly hatched larvae (Mills & Mann 1985). Availability of suitable spawning habitat and nursery habitats for young fish, as well as an adequate food supply during the early stages are therefore critical factors governing the successful recruitment of a species (Pinder, 2005). Moreover, the rapid morphological and physiological changes which occur during early development result in constantly changing ecological demands of a species as well as varying degrees of tolerance to water quality parameters and levels of flow (Flore & Keckeis, 1998). Even prior to hatching it has been demonstrated that cyprinid eggs have varying degrees of tolerance to oxygen levels depending on their state of ontogenetic development (Keckeis et al., 1996). Their relative fragility makes consideration of the requirements of early life history stages crucial to the future management of fisheries globally, and is no less relevant to the ecological functioning of the Mersey and the potential sustainability of fish populations within the catchment. It is not possible to define habitat requirements for larval and juvenile cyprinids as a family, since there is substantial interspecific and intraspecific (among developmental stages) variation. However, some generalisations are possible in terms of key requirements. Post hatching, the littoral zone (close to river bank) is heavily utilised

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by most species (Pinder et al., 2005) as it often offers a refuge from higher current velocities. Macrophytes are also important for providing cover and protection from predators and high water velocities, and encourage the development of algae and associated invertebrates (notably copepods and rotifers, that are important as food for early development stages (Reckendorfer et al., 1999)). Channel connectivity has also been highlighted as an important factor affecting recruitment success, with off river habitats and access to the floodplain and ditches providing spawning habitat, refuge from floods and fluxes of poor water quality, while sometimes also offering rich feeding grounds (Pinder, 2005). (b) Adults Different species of freshwater fish utilise a preferred range of both general habitat and spawning substrata and on this basis have been classified into ecological and reproductive guild systems (Balon, 1975; 1981). Detailed descriptions of guild classifications and ecological requirements of non-salmonid fish are available in Mann (1996). Within the present study, the emphasis is on the reproductive guilds that are of primary interest to the main fisheries currently present within the Mersey system. It is worth noting, particularly in the context of rivers with degraded habitat structure, that some species are capable of displaying varying degrees of plasticity and adaptability in terms of spawning substrate used. As a result it is not uncommon for a species to fit within more than one guild, hence the multi guild classification of phytolithophil (i.e. spawning on both stones and macrophytes). The following relevant reproductive guilds are derived from Balon’s classification but based on known spawning preferences in UK watercourses; A.

Non guarders

A.1.3. Lithophils: Eggs adhere to stones and gravel in moderate to fast flowing water; initially the larvae are photophobic. Barbel Barbus barbus Dace Leuciscus leuciscus Chub Leuciscus cephalus A.1.4. Phytolithophils: eggs adhere to submerged plant surfaces, but other substrata are utilised if suitable plants are absent. Flows range from still to moderate. Roach Rutilus rutilus Perch Perca fluviatilis Bream Abramis brama A.1.5. Phytophils: eggs adhere to submerged macrophytes; larvae are not photophobic. Usually in still or low water velocities. Pike Esox lucius Rudd Scardinius erythrophthalmus Tench Tinca tinca Carp Cyprinus carpio A.1.6. Psammophils: eggs are laid on sand or fine roots associated with sand, washed by running water; benthic larvae are photophobic.

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Gudgeon Gobio gobio

With spawning occurring over an extended period of time, it is pertinent for fishery managers to be aware of the predicted spawning times of certain species (Table 5.3). This information allows the careful management of activities such as dredging and the close monitoring of pollution sources, particularly at times when eggs and early life stages are likely to be vulnerable to these effects.

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Table 5.3 Ranges of spawning dates for fish either already present or potential colonisers of the Mersey catchment Species Trout Salmon Pike Grayling Dace Bullhead 3-spined stickleback Sea lamprey River lamprey Brook lamprey Stone loach Perch Chub 9-spined stickleback Rudd Gudgeon Roach Common bream Silver bream Bleak Barbel Tench Common carp Minnow

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug Sep

Nov

Dec

-----------------------------

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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Oct

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5.2.2 Salmonids (a) Migratory salmonids In addition to demanding better water quality than coarse fish, salmonids are more susceptible to a wide range of anthropogenic impacts. Of primary importance is the ability to navigate between marine and freshwater habitats of suitably high quality to meet their ecological requirements throughout different life stages. Potential barriers to such migrations include instream structures such as weirs and locks, but spatial variation in water quality may similarly create barriers to migration. Due to the specialised life cycle of the Salmonidae, habitat quality, particularly spawning gravels also need to be of higher quality than those utilised by rheophilic coarse fish such as barbel and dace. This is partly due to the temporal differences in incubation times of eggs and the way in which eggs are deposited by the two families. Rheophilic cyprinids typically lay their eggs on the surface of the gravel where they benefit from a constant supply of oxygenated water. The eggs then take between 5-20 days (depending on species and temperature) before hatching, with the many thousands of larvae dispersing downstream to suitable nursery habitats. Conversely, salmonids bury their eggs in excavated gravel structures (redds) where, depending on incubation temperatures, they typically take 10 weeks to hatch, with the “yolk sac fry” (alevins) remaining within the gravel for another 2 weeks, before emerging as “swim up fry” and dispersing to suitable feeding territories. During incubation, the eggs require an adequate flow of water passing through the redd in order to satisfy the oxygen demands of the developing embryos. It is because of this extended incubation period that spawning gravels and redds are often prone to siltation, with the ingress of fine sediments blocking the interstitial spaces between the gravels and thus suffocating the eggs. This is particularly problematic where suspended solids are added to the system, either as industrial/domestic effluents, road or agricultural land run-off, following heavy rain. The extended incubation also renders the embryos immotile and unable to relocate in order to avoid sporadic spates in poor water quality, thus making them more vulnerable to episodic pollution events. Salmon Following hatching, salmon ‘fry’ occupy marginal habitats before moving as ‘parr’ into the main flow with gravel substrates, where they typically compete for feeding territories throughout the summer. As water temperatures begin to drop in the autumn, parr tend to relocate into slightly deeper water with reduced velocities, with diel hibernation frequently reported when water temperatures drop below 10oC (Rimmer, Paim et al. 1983; Valdimarsson, Metcalfe et al. 1997). This involves parr becoming nocturnal, using refuges within the substrate during the day while actively feeding during the hours of darkness (Metcalfe et al 1999; Whalen and Parrish 1999). Shelter from predators appears to be of key importance during winter and severe bottlenecks in production may occur if there is insufficient deep area or rough substratum to afford shelter (Armstrong and Griffiths 2001), Indeed, (Rimmer, Paim et al. 1983) reported that substrate chambers were exclusively selected in a New Brunswick river, over all other shelter types. Stream bed refuges were considered to be of critical importance in the over wintering of salmonids (Cunjak 1996), with extensive

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competition having been observed between individuals for the use of such refuges where these habitats were limited (Griffiths and Armstrong 2002; Harwood et al. 2002). Thus, the abundance of shelters is believed to be an important factor regulating the salmonid carrying capacity of streams during winter (Cunjak 1996; Armstrong and Griffiths 2001; Miyakoshi et al., 2002; Rimmer et al., 1983). In a recent review of habitat management for the rehabilitation and enhancement of salmonid stocks (Hendry et al., 2003) recommend the provision of a coarse substrate of predominantly cobbles and boulders, ranging from 64 to 256 mm, in order to provide shelter for older parr. Duration of the life cycle varies both between and within populations. Depending on water temperatures, food availability and ultimately growth, parr can occupy these freshwater habitats for one or more years before smolting in the spring and commencing their journey to the sea. These fish will then spend one year (grilse) or more (multi sea winter (MSW)) at sea before returning to their natal rivers to spawn. The timing of this migration is variable but typically the larger (MSW) fish enter rivers in early spring, with the smaller grilse returning later during late spring/early summer. Although the different age groups enter the mouths of rivers at different times it is not unusual for these fish to occupy habitats in the estuary or lower river, before continuing their journey towards spawning grounds closer to the spawning season in November to January in mixed year classes. Sea trout Sea trout are the migratory form of brown trout Salmo trutta. Unlike salmon there is not a requirement for these fish to migrate to sea in order to complete their life cycle and thus many isolated and genetically distinct populations of brown trout can be found in many upland streams and hill lochs. Where passage to the marine environment is an option, a proportion of the juvenile stock may smoltify (Maitland & Campbell, 1992) in order to migrate to the sea. As well as facilitating both enhanced growth rates and reproductive potential, riverine fishery value is also greatly increased due to the exploitation of stocks for angling purposes. Habitat requirements are not dissimilar to salmon, although juvenile habitats differ subtly in that trout prefer slightly slower flows, deeper water and greater cover from both instream and outstream structures (Table 5.4).

(b) Non migratory salmonids Brown trout Populations of the non-migratory form of Salmo trutta occupy a range of different habitats, demonstrating a certain degree of plasticity in their requirements. This said, in order to reproduce, suitable clean gravel habitats must be available in order to excavate redds for the deposition of eggs. Spawning and early life history within the redds is essentially the same as salmon, although spawning substrates tend to be of a smaller particle size. This is because the smaller body size of the adults restricts the size of stones which can be moved. Adults, which typically range from 15-30 cm, occupy a range of habitats including pools, undercut banks and gravel runs.

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Population health of brown trout stocks is often positively correlated with increased habitat complexity. While Table 5.4 details a simplified description of salmonid habitat requirements, it also provides a useful tool for the determination of habitat availability within a river and forms the framework used to conduct earlier habitat surveys on the Rivers Bollin and Goyt (APEM scientific reports 699 & 763). For a comprehensive review of habitat requirements of Atlantic salmon and brown trout see Armstrong et al. (2003). Table 5.4 Habitat classification system HABITAT TYPE DESCRIPTION Spawning Gravel Ideally stable but not compacted, with a mean grain size 25 mm or less for trout, but up to 80 mm for salmon. ‘Fines’ (1+) habitat Riffles Glides

Pools

Shallow, < 20 cm deep, fast flowing (>30 cm/s), with surface turbulence and a gravel and cobble substrate. 20 – 30 cm deep, fast flowing (>30 cm/s), surface turbulent, gravel/cobble/boulder substrate. Shallow, < 30 cm deep, fast flowing (>30 cm/s), Surface turbulent, gravel/cobble/boulder substrate. = or > 30 cm deep, moderate velocity in range 1030 cm/sec, surface smooth and unbroken, relatively even substrate of cobbles with finer material. = or > 40 cm deep, slow-flowing (< 10 cm/s), surface unbroken, substrate with a high proportion of sand and silt.

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6.0 FISH POPULATIONS, STOCKING ACTIVITY AND EVIDENCE OF NATURAL RECRUITMENT Analysis of Environment Agency stocking records has revealed how frequently fish have been stocked to the upper Mersey catchment in the last two decades. These records are likely to be incomplete but show that in excess of 0.5 million fish have been stocked over this time period. The frequency of stocking and the lack of data regarding size and age structure of those fish stocked make it problematic to identify recruitment which has occurred naturally and therefore very difficult to identify the environmental factors causing recruitment bottle-necks. Further problems arise from the sampling methodologies being currently employed to assess fish stocks. These methods are ill designed to capture larval and juvenile fish, which are key indicators of not only successful recruitment, but also of water quality and the quality of physical habitat. To assess the self-sustainability of fish populations, each part of the catchment will be considered in turn, taking into account both stocking records and fish survey results.

6.1 Lower River Irwell and upper Manchester Ship Canal The Lower River Irwell and its major tributaries, the Rivers Irk and Medlock have been subject to extensive stocking over the last 15 years with the addition of 120,600 individual fish. Table 6.1 shows the stocking history of the Irwell, for which detailed records are available). Due to the inevitable downstream displacement of stocked fish (Linfield, 1985), these records need to be closely scrutinised in considering the natural recruitment of fish populations of the Lower River Irwell and the upper MSC. Table 6.1 River Irwell stocking history Year Species 1995 chub dace trout 1996 chub dace 1997 chub roach 1998 chub 1999 chub 2001 trout chub TOTAL

No. Stocked 5000 5000 2500 4000 4000 5000 2500 1500 8000 4000 6000 47,500

Size range

7 inches

2-4.5 inches 10.6 cm (mean) 10-16cm

6.2 River Irwell Upstream of Bury Environment Agency surveys carried out between 2005-2006 at 5 sites upstream of Bury, indicate that the upper River Irwell supports a mixed fishery dominated by minor species such as minnow and stone loach. When considering species of a sporting interest, gudgeon, trout and chub dominate with good numbers of roach also

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present. Although the survey reports do not provide any data regarding age structure, it would appear from stocking records that the upper river functions in a selfsustainable manner, with adequate recruitment evident for most species. The one exception according to available data is that dace are not successful in this river with only two specimens captured over a two-year period. This said, dace are a highly mobile species and a more comprehensive survey may reveal that they contribute more substantially to the overall composition of fishes.

Species composition (%) of River Irwell u/s Bury. 2005-2006 data combined Brown trout Perch

N=3127

Pike Chub Gudgeon Roach Bullhead Minnow Stickleback Stoneloach Dace

Figure 6.2a

Species composition (%) of River Irwell u/s Bury. 2005-2006 data combined (minor species removed from analysis 0.3% 5.9%

15.7%

Brown trout

3.3% 0.4%

Perch Pike Chub Gudgeon

16.1%

Roach Dace

58.3%

Figure 6.2b

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6.3 River Irk Very little data exist for the River Irk. In 2004 three sites were electric-fished by the Agency and these surveys revealed an abundance of three-spined stickleback along with two minnows and a single adult brown trout. Assuming that the three sites surveyed were representative of the river, then it would appear that the 1990’s stocking programme of the Irk (see Table 6.3 below) has been far from effective. Sporadic peaks in BOD and ammonia suggest that combined sewer overflow (CSO) discharges may be responsible for a lack of recruitment success in the Irk. Table 6.3 River Irk stocking history Year Species 1994 trout minnow 1998 dace chub TOTAL

No. Stocked 3000 2500 4000 1000 10,500

Size range

6.4 River Medlock Agency surveys were carried out at five sites between Woodhouses and Clayton Vale over a three-year period of 2004-2006. The population structure was dramatically dominated by minnows (76%), with minnow, stickleback and stone loach making up 98.5% of the total population. In order of ascending dominance, the remaining species consisted of relatively small numbers of chub, trout, perch, roach and pike. In light of significant stocking of roach and chub in particular (see Table 6.4 below), the available data strongly suggest that there is a severe recruitment problem of species of fisheries interest on the River Medlock. This is despite a dramatic improvement in water quality, with BOD, DO and ammonia all conforming to EC FFD targets for the majority of the time. However, the Medlock is still subjected to sporadic CSO discharges (as detected in March 2005, Fig A7b, Appendix 1). Should these isolated events correspond with spawning seasons, then CSO discharges may be responsible for the death of eggs and young larvae in the Medlock.

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Table 6.4 River Medlock stocking history Year Species No. Stocked 1993 Chub 1500 Minnow 3600 Dace 1000 1995 Chub 3000 1996 Chub 8000 1997 Chub 18000 Dace 15000 1998 Chub 4500 Roach 4000 1999 Dace 1000 Chub 3000 TOTAL 62,600

Size range

Species composition (% ) of R. Medlock 2004-2006 data combined 1.5%

N= 6535

minnow, st'back,st loach others

98.5%

Figure 6.4a

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Species composition (% ) of R. Medlock 2004-2006 data combined (minor species removed from analysis) 1%

N= 93

Chub 39%

42%

Perch Roach Brown trout Pike

8%

10%

Figure 6.4b

6.5 Lower River Irwell and upper MSC Fish Survey data Fish population data for the lower River Irwell and upper MSC are lacking from Environment Agency records. However, APEM carried out surveys between 19982000 and 2004-2006. It should be noted that the initial surveys between 1998-2000 were carried out prior to the initiation of the oxygenation programme. 6.5.1 Surveys, 1998-2000 These early surveys combined sampling methods over a stretch of water between Salford University on the River Irwell and the Turning Basin of the MSC. Data from fyke nets, electric fishing and anglers records from 6 survey zones, between March 1998 and February 2000 are presented in Figure 6.5. Roach and perch dominated these early surveys, contributing 53% and 37 % respectively to total species composition. Chub, dace, trout and a single gudgeon were also caught in the main channel sections. Additional species captured within Wilburn St. Basin included pike, bream, rudd and single specimens of tench and carp (Table 6.5). In addition to stocking records made available by the Environment Agency, additional stockings activity is also reported by Nash et al (2003). The further addition of 9,500 roach and 12,000 chub to the Irwell, and 19,000 dace and 30,500 chub to the tributary rivers, the Irk and Medlock during 1997-1998, make it almost impossible to decipher where the fish caught in this survey had originated. In the absence of any records of artificial stocking, perch showed good recruitment for the 1998 year class, with three 0+ perch also caught in August 1999 signifying another successful year. 0+ roach were also caught in Wilburn St. Basin in 1999, indicating that some degree of recruitment occurred in this year. It must be remembered that the sampling methods were not suited to 0+ fishes and their absence

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or presence of only small numbers of a species is unlikely to be a true reflection of their abundance. By studying back-calculated length/age analysis of fish populations in conjunction with stocking records, it is usually possible to identify recruitment patterns. What these data do not demonstrate is whether recruitment occurred within the stretch of water under consideration, or whether adult fishes of mixed ages have immigrated into the reach after recruiting elsewhere in the system. From the data available, it appears that at this time, dace, chub and trout were failing to recruit in the lower Irwell and MSC with no dace caught under the age of 4 +, despite the availability of faster flowing, well oxygenated water below Adelphi Weir. The lack of these species in the early stages of development suggests that either water quality or habitat constraints are acting as a bottleneck to the recruitment of the rheophilic species. In addition to these records, previous APEM reports also noted various observations of spawning behaviour and the presence of eggs throughout the reach. Cyprinid eggs were observed in Wilburn St. Basin, although these were rapidly killed by fungus. Cyprinids of unknown species were also observed spawning in the lower Irwell, although no eggs were recovered and shoals of unidentified cyprinid fry were caught from the Turning Basin. The distinctive ribbons of perch spawn were also found in both the Turning Basin and below Adelphi Weir but all eggs became opaque within 24 hours of spawning. This observation in particular suggests that fertilisation had not taken place, perhaps as a consequence of the frequency of intersex observed within the population of male perch, as discussed later.

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zone 2 trout

Zone 3

roach perch

dace

roach

dace

perch

Chub zone 6

chub

bream pike

Wodden Basin rudd pike carp tench bream

perch

dace

roach

zone 4 bream gudgeon

perch

roach

perch roach

Zone 5 trout

roach

500 m

perch

Figure 6.5 Fish community structure along the lower River Irwell and upper MSC between March 1998 and February 2000.

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Table 6.5 Total number of fish caught by specific sampling methods in each survey zone of the lower River Irwell and upper MSC (A angling, EF Electric fishing, FN Fyke netting, GN Gill netting), from March 1998 to February 2000. Zone 2

Zone 3

Zone 4

Species

A

A

FN

A

Roach Perch Pike Bream Rudd Chub Dace Trout Tench Gudgeon Carp TOTAL

1 4

9 3

11 55

201 33 3

16 6 2

312 334 32 27 28

Zone 5 FN

EF

FN

GN

EF

15 5

14 27

33 15

117 5

8 12 3 1

1 1

22

67

238

1 1 1 736

20

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Zone 6

1 10

1 29

Wilburn St. Basin EF

42

48

122

25

Total catch

% of catch

721 493 35 31 28 17 17 3 1 2 1 1349

53.4 36.5 2.6 2.3 2.1 1.3 1.3 0.2 0.1 0.1 0.1

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6.5.2 Surveys, 2004-2006 More recent survey data are available for the years 2004-2006, although these surveys utilised just the single method of fyke netting, with fyke traps placed at a number of sites betwen Mode Wheel lock and the entrance of Wilburn St. Basin. In order to account for the restricted number of nets deployed and the known mobility of fish populations, all data have been combined for each year to facilitate analysis of the results (Fig 6.5b). The 2004 survey revealed a striking shift in species composition from the earlier surveys, with gudgeon dominating the catch. This has been the case since, and is encouraging since these gudgeon must have recruited naturally. Gudgeon are known to show plasticity in their habitat requirements. Although typically classified as psammophilic (spawning on sand) they are also known to spawn on aquatic moss (Fontinalis) in well oxygenated water; such conditions are thought to exist at Adelphi Weir (Pers observation). The current spawning and nursery habitats of this fish are presently unknown on the MSC, but efforts should be made to identify and protect these habitats in order to maintain the stock. The lack of 0+ gudgeon in any surveys confirms that the sampling methods used for these surveys are unsuitable for the capture of 0+ fishes. Temporal changes in species composition in the upper MSC (all data pooled from fyke samples only) N=135

N=267

N=116

N=298

100%

80% Rudd C. bream Roach Minnow Gudgeon Perch

60%

40%

20%

0% 1998-2000

2004

2005

2006

Figure 6.5b Temporal changes in species composition in the upper MSC and lower River Irwell between 1998 – 2006

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An alternative sampling approach was trialled in 2005 with the use of a ‘boom boat’ for electric fishing. Although this sampling gear was not designed for the capture of juvenile fish, this one-off survey produced a good number of 0+ chub, gudgeon, roach and stickleback, confirming for the first time that successful recruitment was taking place on the lower Irwell and upper MSC. This suggests that previous sampling methodologies have not been adequate to either indicate or assess levels of recruitment.

Irwell adjacent to Wilburn St Basin October 2005

Total number of fish = 337 Ch ub Gu dgeon Pe rch Ro ach St ickleback

Fig 6.5c Boom boat electric fishing survey in the River Irwell near Wilburn Street Basin. With the exception of perch all other fish were 0+ providing the first indication of good recruitment. With the exception of the above data, the paucity of such records emphasizes an urgent need to carry out surveys specifically designed for the capture of 0+ fishes (Copp, 1989; Pinder, 2001) in order to assess the performance, water quality and habitat constraints, and the self sustainability of fish populations in the Irwell and MSC. Without such data, the effective management of these fisheries will always be compromised and informed decisions cannot be made regarding the need for additional stocking or habitat manipulation. Consideration of the health of the adult stock, using a length weight relationship to assess condition, indicated that fish of all species were generally healthy in all years, with growth exceeding the ‘Hickley Standard’ and both growth and condition within the oxygenated Turning Basin exceeding those values found elsewhere in the upper canal and lower Irwell. This is discussed in detail in Section 7.

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6.6 Salford Quays Table 6.6 Stocking history Year Species 1988

1989

1997 1998 2002 2004 2006 TOTAL

Bream Carp Roach Rudd Tench Carp Chub Dace Perch Roach Rudd Chub Roach Tench Tench Rudd Roach

No. Stocked

Weight(lbs) Stocked 17.5 60 17.5 17.5 17.5 400 100 100 200 1000 400

500 1500 1000 1070 1000 1000 6,070

Location Size range (comments) Basin 7c 70 lbs mixed

Basin 7a

2200 lbs mixed

Basin 7a

12-15 cms

Basin 7a Basin 7a Basin 7a Basin 7a

12-15 cms 12-15 cms 12-15 cms 12-15 cms

2330

Salford Quays fish survey data Immediately after isolation of the Quays from the MSC in 1986, the only fish present were a small population of roach and three-spined stickleback. The diversity of fish within the Quays has since been enhanced by stocking, habitat diversification and natural recruitment and today the Quays support a wide range of species. The dramatically improved water quality in the Quays make this an ideal model on which to study how further improvements in the adjacent Ship Canal could benefit future fish populations.

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100%

N=126

N=78

N=133

N=237

N=100

N=352

N=112

N=190

80% 60% 40% 20%

2006

2005

2004

2003

2002

2000

1999

1988-1990

0%

eel pike trout tench r x b hybrid rudd roach perch chub carp bream

Figure 6.6 Temporal changes in species composition in Salford Quays (three-spined stickleback removed from 1988-1990 data)

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The design and lack of shallow littoral habitats within Salford Quays, makes sampling fish populations problematic. Since the isolation of this water body from the MSC, sampling techniques have varied, both in terms of effort, areas sampled and methods used. Therefore data have been combined from all areas for fish captured by angling competitions, fyke netting, gill netting and electric-fishing. Because of these various sampling inconsistencies, data need to be treated with some caution and may not be a true reflection of the current status of the fishery. Figure 6.6 summarises the changing species composition between 1988 – 2006. Sticklebacks have been omitted from the 1988-1990 data set. At this time, this species dominated the population, but none have been caught since 1992. Maintenance of diverse fish populations in Salford Quays currently relies heavily on stocking practices. Although roach have been successful in recruiting on a number of occasions, available data suggest that this species has struggled to recruit on a consistent annual basis, since the late 1990s. Perhaps at the expense of the roach population, perch have become very successful with recruitment evident from 1991 onwards. There is little evidence of other species succeeding in recruiting although three 0+ dace were captured in February 1992 and several 0+ pike were caught in 2005. Due to the spawning requirements of these species, it seems unlikely that these fish were produced within the Quays and were perhaps discretely stocked by anglers. Although carp, bream and tench are still occasionally caught or observed, these are adult specimens and show no signs of being able to maintain their population numbers naturally, despite the limited success of artificial spawning media (Nash et al., 1999). Worthy of note was the capture of a 40 cm eel in Dock 7 during an electric fishing survey on November 17, 2005. This specimen represents the only record of this species to be captured upstream of the River Bollin since the Industrial Revolution. The journey that this fish had undertaken to find a home in Salford Quays is a mystery, although the possibilities of this fish travelling across land from a neighbouring canal (such as the Bridgewater), or that it had been introduced by an angler should not be dismissed.

6.7 Upper River Mersey Fish survey data are extremely limited for the upper Mersey. Due to heavy rainfall preceding an Environment Agency survey in 2004 the Mersey was unfishable and the survey was restricted to two sites on the Micker Brook, a tributary of the Mersey. A survey the following year was conducted at two sites on the Micker Brook and at three sites on the Mersey between Heaton and Little Ees Lane. Very few fish were caught from the combined surveys and therefore a robust assessment of the fish population is not possible. Although a total of 12 species were recorded, only small numbers of each species were caught, with several species such as tench and crucian carp having probably escaped from an ornamental fishery neighbouring the Micker Brook.

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Table 6.7a: Stocking history Year Species 1996 chub 1997 roach chub dace 1998 roach chub 1999 dace 2000 dace roach 2001 chub roach Total

No. Stocked 15000 15000 29000 6000 13000 9000 7000 7000 5500 26000 5000 149,500

Table 6.7b: River Mersey Fish Survey data Year Species No. Stocked 1993 chub 20000 dace 6000 roach 6000 1994 barbel 1700 1995 chub 10000 1996 chub 1500 dace 1500 1997 roach 5000 dace 7000 2000 dace 12000 2001 chub 13000 dace 3500 trout 2500 2003 grayling 2000 Total 91,700

Size range

Size range

The presence of 0+ roach, trout and perch in the Micker Brook confirmed successful spawning of these species in 2004, with the presence of 1+ dace and gudgeon and 2+ roach in 2005 also suggesting that recruitment of these species had occurred in 2004 and 2003 respectively. Although more detailed surveys are required, it would appear that the upper Mersey supports a mixed coarse fishery with some brown trout. The available data suggesting that these populations are to some extent self-sustainable.

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6.8 River Goyt Table 6.8 Stocking history Year Species 1993 chub dace roach 1994 barbel 1995 chub 1996 chub dace 1997 roach dace 2000 dace 2001 chub dace trout 2003 grayling Total

No. Stocked 20000 6000 6000 1700 10000 1500 1500 5000 7000 12000 13000 3500 2500 2000 91,700

Size range

River Goyt Fish survey data Combined data from five sites surveyed by the Agency in 2004, revealed high species diversity in the River Goyt. Species composition was dominated by minor species, with stone loach, minnow and bullhead making up 76% of the total number of fish. The remaining 24% comprised 141 fish of 12 species, the relative abundance of which are summarised in Fig 6.8. Natural recruitment was evident for several species, with the first record of a juvenile barbel from the Goyt representing the first evidence of spawning success in this species. 0+ roach, perch, grayling and trout were also caught suggesting that a range of both rheophilic and limnophilic habitats are available. In light of the evidence that these species had spawned successfully, it is perhaps surprising that no chub or gudgeon were caught under 4 years of age. However, this may be due to the limited scope of the survey and it is quite possible that these species are successful at other sites along the river where specific habitats are perhaps more favourable. In addition to the survey data made available, In 2005, four salmon parr were recorded from the Goyt (see section 10).

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Species composition (% ) in the River Goyt 2004 (minor species removed from analysis) 1% 22%

N=1

8% 10%

Barbel Trout Chub Common bream Grayling

3%

Gudgeon

20%

1%

Pike Perch

2%

Roach

2%

Rainbow Trout

1%

5%

3-Spined Stickleback Brook Lamprey

25%

Figure 6.8

6.9 River Tame Table 6.9 Stocking history Year Species 1996 chub dace trout 1997 roach chub dace 1998 chub dace roach 2001 dace Total

No. Stocked 13000 9000 4000 2000 15000 5000 4000 2000 3000 2500 59,500

Size range

5-7” 2-4” 2-4” 2-4” 2-4” 5-15 cm

River Tame Fish survey data Although age data were not available from the most recent survey, earlier Agency reports from 2003 confirm good recruitment of trout, chub and gudgeon, with a small number of 0+ grayling also present. In 2005, five sites were electric fished between Mossley Mill and Triviot Bridge. This survey showed minnow to be numerically

dominant (38%) with gudgeon, chub and trout being the prominent species of fisheries interest. In accordance with other rivers in the system, dace have been poorly represented in previous surveys on the River Tame.

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Species composition (%) in the River Tame 2005 (minnow removed from analysis) 10%

0.2%

0.5% N=467

17%

1% 19%

11%

3.3%

Brown Trout Chub Gudgeon Roach Stoneloach Bullhead 3 Spined Stickleback Dace Pike

38%

Figure 6.9

6.10 River Bollin Table 6.10 River Bollin stocking history Year Species 1995 Chub 1996 Chub Dace 1997 Dace Perch Roach 1998 Roach 1999 Roach Rudd 2003 Trout 2004 Trout 2005 Trout 2006 Bream Barbel Chub Gudgeon Total

No. Stocked 1000 4000 1000 3000 2000 10000 150 7334 1166 200 250 150 200 200 100 1000 31,750

Size range

20cm 20 cm 16-20cm 20-25cm 20-25cm 7-12cm

River Bollin Fish Survey data Data from fish surveys have been made available by the Environment Agency for surveys conducted at six sites between Styal Weir and Heatley Mill during 2004 and 2005. A total of 13 species were caught over this period and are detailed in Table 6.10. In both years chub and gudgeon dominated catches with perch and roach also being widely distributed among sites. Based on previous data collected by the Agency, species composition and distribution had remained constant between 2001

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and 2005, with a constant increase in ‘standing crop’ observed over the same fouryear period. Spatial differences were evident, with the section downstream of Heatley Weir proving to be the most prolific in terms of both standing crop and species diversity in all surveys. The Weir at Heatley has been identified as an impassable barrier to most fish migration (APEM, 2004), with limited scope for rheophilic spawning between Heatley Weir and the MSC. From the available survey results, it would appear that dace are largely confined to this area of the Bollin and if upstream passage of the weir were possible, the dace population would be expected to benefit from the availability of additional spawning substrate further upstream. Although dace were the only species to demonstrate poor growth rates and little evidence of natural recruitment, a single juvenile barbel was captured in this section in 2005. This is the first evidence of natural recruitment in this species recorded on the Bollin. Again the ability of this species to gain access to the river above the weir is only likely to benefit the population. While dace showed poor growth rates compared with the ‘expected standard’ for northern rivers, all other species demonstrated average to fast growth and confirm adequate availability of food to maintain the current population levels. During the 2004 survey successful recruitment was confirmed by the capture of 0+ chub, perch, gudgeon, pike and brown trout. The presence of chub, gudgeon, perch, roach and trout in the 1+ age class also indicated recruitment of these species the previous year. In 2005 no 0+ fish were caught. Although 0+ dace were absent from both surveys, age classes ranged from 4+ to 5+ and 2+ to 7+ in 2004 and 2005 respectively. If the stocking records detailed in Table 6.10 are complete, this would indicate sporadic recruitment being achieved prior to 2003. With the close proximity of the MSC to the lower survey site it is obviously of great interest to establish whether fish populations are restricted to the lower 2.9 km of the River Bollin or if migration occurs between the MSC and lower Bollin when water quality conditions allow. Adult salmon have been observed leaping at Heatley, indicating that during autumn at least, it is possible for migrating fish to cross the MSC.

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Species composition (%) in the River Bollin 2005 (minor species excluded from analysis) 0.2% 0.2%

Brown trout

1%

Chub

N=515

16%

Dace

0.2%

Eel

33%

1%

Gudgeon Perch Pike

26%

Roach

0.4%

Barbel

22%

Figure 6.10 In contrast to the rivers of the upper Mersey catchment, a small number of eels have been recorded from the Heatley Weir stretch. This is evidence that this species is again entering the lower Ship Canal in search of freshwater rearing habitat. It is not clear whether the eels caught in the Bollin, entered the river as elvers or as relocating juveniles.

6.11 Rivers Weaver and Gowy Species composition in the Rivers Weaver and Gowy flounder tench

100%

rudd eel

80%

ruffe 60%

gudgeon

40%

bream perch

20%

roach dace

0% Weaver

Gowy

chub trout

Figure 6.11 The River Weaver species composition has been calculated using the combined records from 24 angling matches, based on each species frequency of capture. Data

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from the River Gowy were collected from electric fishing surveys carried out in 2004. (All data provided by the EA). The Rivers Weaver and Gowy are worthy of mention in this review because of their more direct connectivity with the Mersey Estuary. The River Gowy is ducted beneath the MSC thus benefiting form a direct migration route, while the Weaver flows into the MSC before entering the estuary after crossing the MSC at Weaver Sluices. The most striking difference between these rivers and the upper catchment is the abundance of eels in these rivers. This illustrates that the Mersey estuary still has a healthy run of elvers, but migration appears to be impeded by the MSC with eels only recorded in small numbers as far up as the lower River Bollin.

7.0 FISH HEALTH 7.1 Growth Rates Growth rates are commonly used as an indication of both individual and population health. Calculated retrospectively from the back-calculation of annual length increments from the relative distances between scale annuli, this method allows useful comparisons to be made between populations on a spatial scale and also in relation to expected ‘National Standards’ (Hickley & Dexter 1979). Where observed growth values are below these standards, an environmental constraint is likely to be the cause. On examination of Environment Agency data, it would seem that the Mersey catchment as a whole, currently promotes growth above the expected national average in most species. Data from recent surveys reported roach populations attaining 105 and 116% of the ‘Percentage Standard Growth’ (PSG) in the upper Mersey and River Bollin respectively. Likewise, chub attained 112% of the PSG in both the upper Mersey and the Bollin. In some instances, rheophilic species such as dace demonstrated reduced growth rates of 89% on the River Bollin, suggesting that habitat within this particular section of the Bollin is of insufficient quality to favour the success of this species. Recent growth of roach year classes in the MSC (Fig 7.1) indicates that, although initial growth rates lie below the Hickley Growth Standard, from the age of 4+ growth rates increased to above the expected average. While inter-annual abiotic factors such as temperature can influence growth rates, Figure 7.1 mirrors what has been observed throughout the catchment and emphasises that current growth rates generally exceed national expectations and suggest adequate food supply and healthy physiological composition of the majority of these populations throughout the catchment, including the MSC.

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300

MSC 2006 MSC 2005 MSC 2004 MSC 2003 SQ 1999 R.Thames 1967 Standard

250

Length (mm)

200

150

100

50

0 1

2

3

4

5

6

7

8

Age (years)

Figure 7.1 Growth Standard Curve. Growth rates for roach in the MSC, Salford Quays and the River Thames (at the time of sampling, the latter represents an environmentally stressed population). Also shown is the Hickley Growth Standard

7.2 Condition The weight and length of fish are related by a power relationship (W = a L b), where the value of b can be used as a measure of fish condition. Condition is the volume of a fish relative to length and this is taken as a measure of well-being, such that better condition is assumed with increasing volume (or weight) for a given length. As the relationship is dependent on volume, b usually has a value around 3.0. To maximise the number of data points, the power relationship was plotted using roach data from all surveys conducted on the MSC during 2006 (Fig. 7.2a), which generated a power value (b) of 2.9. This value is slightly lower than the figure derived from 2005 data of 3.3. Nevertheless, the value of 2.9 is still very close to the ‘ideal’ of 3.0. Furthermore, the figure generated when only data from the oxygenated region are plotted exceeds 3.0, (3.1) (Fig. 7.2b). Undertaking the same analysis for all perch data also produces a figure of 2.9 (Fig. 7.2c). Overall, these values indicate that fish in the MSC were in very good condition.

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300

250

2.9149

y = 2E-05x R2 = 0.9441

Weight (g)

200

150

100

50

0 0

50

100

150

200

250

300

Length (mm)

Figure 7.2a Length / weight relationship for roach caught in the upper MSC during summer 2006

160

y = 9E-06x3.1041 2 R = 0.9978

Weight (g)

120

80

40

0 0

50

100

150

200

250

Length (mm)

Figure 7.2b Length / weight relationship for roach caught in the oxygenated region of the upper MSC during summer 2006

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300

250

y = 2E-05x2.9274 2 R = 0.9344

Weight (g)

200

150

100

50

0 0

50

100

150

200

250

300

Length (mm)

Figure 7.2c Length / weight relationship for perch caught in the upper MSC during summer 2006 7.2.1 Fulton’s Condition Factor A further measure of fish condition is provided by Fulton’s Condition Factor (K = W / L3, where W is weight and L is length). The formula is again based on the assumption that for a given length a heavier fish is in better condition. Figure 7.2d provides an inter-annual mean condition comparison for all roach and all perch caught in Salford Quays between 1988 and 2005. The subtle temporal negative trend in condition of both species is most likely a reflection of a decrease in density of pollution tolerant invertebrates, which has been observed to be negatively correlated with decreasing nutrient availability and improving water quality.

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Annual mean Fulton's K value (+/- SE) for roach and perch in Salford Quays

Fulton's K value

2

Roach Perch Linear (Perch) Linear (Roach)

1.5

2005

2003

2001

1999

1996

1994

1992

1990

1988

1

Figure 7.2d

7.3 Food availability To date, a comprehensive survey of fish diet within the MSC and surrounding watercourses has not been carried out. However, preliminary ‘snapshot’ investigations into the diets of roach and perch have revealed opportunistic feeding behaviour in accordance with those prey items available within different areas of the Canal. In particular, within the Quays, perch diet was dominated by Copepods and Chydorous, while in the Ship Canal and the Wilburn St. Basin, more pollution tolerant species featured in the guts of perch with Assellus sp. dominating with leeches and young fishes also present in those perch feeding in the Wilburn St. Basin. Roach also showed plasticity in their food intake, with the ‘Quays fish’ ingesting much greater quantities of detritus, sediment and vegetation. These less nutritious items made up 60% of the gut contents, with the remaining 40% consisting of Chironomidae and copepods. Outside the Quays in the MSC, Assellus sp. dominated, and in Wilburn St. Basin Chydorous and copepods formed the principal prey items. In respect of these limited observations it should be noted that populations within the MSC are mobile and can therefore exploit different food resources on both a temporal and spatial basis. In contrast, the populations within the Quays are restricted to whatever prey are available, with changes in abundance and species only likely to occur on a temporal basis. Another factor highlighted in a previous report (Nash et al., 2003) was the availability of angling baits such as Chironomidae, which may temporarily skew the balance of food naturally available within the Salford Quays area. Despite fish having to demonstrate plasticity in their feeding preferences and the significant intake of detrital material by roach in Salford Quays, food availability does

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not appear to be compromising the health of fish within the Quays or the MSC, as growth and condition factors are often in excess of the national averages. High nutrient and organic inputs from the River Irwell accumulate within the deep, slow flowing sections of the upper Ship Canal and have a fertilising effect, encouraging the proliferation of pollution tolerant species, such as Assellus. Where there is a local abundance of such taxa within the Canal, roach have been observed to capitalise on this resource as foraging time is reduced thus benefiting bioenergetics (Nash et al., 2003). Since the initiation of the oxygenation programme within areas of the MSC, the observed improvements in water quality have also been reflected in the macro invertebrate communities present. Essentially the increase in DO levels have allowed a much greater diversity of animals to colonise these areas and the species count has increased from four pollution tolerant species (pre oxygenation) to a total of 39 invertebrate taxa recorded to date. Although species diversity has shown a dramatic increase, total biomass of available fish food has decreased within the oxygenated areas. This is due to the relative reduction in numbers of pollution tolerant species and it is predicted, from observations on other rivers recovering from organic pollution, such as the Trent, that as water quality improves further, growth rates will become reduced, falling in line with the ‘national average’. During early development, larval and juvenile coarse fishes are restricted in terms of their diet by the gape of the mouth (Pinder & Gozlan, 2004). It is therefore imperative that the availability of sufficient quantities of suitable food corresponds with the hatching of larvae in order to ensure adequate survival and successful recruitment, (Mills & Mann, 1985). During early ontogeny, feeding behaviour is complex, varying both inter- and intra-specifically (Pinder et al., 2005). While some species demonstrate varying degrees of plasticity in their requirements, others are more specific and where suitable food is not available the year class will fail. As a generalisation, cyprinid larvae initially require an abundance of rotifers followed by larger crustacea such as Cladocera, before switching to larger macro invertebrates and detritus, which may be grazed from macrophytes and man-made structures, such as weirs and bridges (Mann et al., 1996). The dietary requirements of perch are, however, more specific with the first few hours after absorption of yolk reserves being a critical period when large quantities of rotifers are needed in order to progress to the next ontogenetic step. Subsequently, due to an increase in mouth gape, larger prey items may be taken. Although the environmental parameters driving the production of such food are complex, it is generally recognised that water temperature and turbidity play important roles in the primary production of algae, (on which many rotifers feed) with phytoplankton models showing a positive correlation with fish recruitment rate (Biktashev et al., 2003). To summarise, although the availability of larger food items is currently plentiful and does not appear to be restricting adult performance, it is not possible at present to ascertain whether recruitment is being restricted by a lack of appropriate food items, to satisfy early stages of development. In order to elucidate whether food availability is limiting fish populations a detailed examination of the status of 0+ fish and their gut contents will be required.

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7.4 Endocrine disruption Following the initial discovery of this phenomenon, endocrine disruption has been a major avenue of research internationally, with a wide variety of chemicals now known to disrupt normal endocrine function in fishes (Sumpter, 2002). Based on the epidemiological data sets of the U.K. and Europe, it is now acknowledged that the occurrence of feminised fish is associated with effluent discharges and that the incidence and severity of feminisation is positively correlated with the proportion of treated sewage effluent in receiving waters (Gross-Sorokin et al., 2006). Although fish are thought to be susceptible to the effects of such pollutants throughout adulthood, direct-exposure studies with early life-stage roach (from fertilized egg and juveniles) confirm that sewage effluents induce a number of feminizing effects. These include vitellogenin induction and duct disruption in the very earliest stages of development (Gimeno et al., 1997), with the effects of duct disruption being irreversible (Gross-Sorokin et al., 2006). Intersex has sometimes been stated to be a rare condition in fish younger than 3 years of age, implying that the expression of this condition is progressive and appears at, or after, the onset of adulthood (Environment Agency 2002a). However, Beresford et al. (2004) reported the detection of endocrine disruption in juvenile roach, using the formation of an ovarian cavity as their main criterion for assessing the degree of oestrogenic activity. This paper demonstrates the advantage of monitoring for feminising effects using juvenile fish, that are initially more abundant, rather than sacrificing sexually mature recruits from an already fragile community, some of which may be capable of successful reproduction. 7.4.1 Occurrence of intersex in the MSC With up to 90% of the dry weather flow of the lower River Irwell and MSC, still, at best, treated sewage effluent, it is of no surprise that the feminisation of several species has been observed from these watercourses. In contrast to the MSC, Salford Quays have not received any sewage effluent or surface water since their isolation from the MSC in 1987 and they, therefore act as a valuable control in order to assess the impact of sewage inputs on the feminisation of local populations. Between 1998 and 2001, 78 roach and 19 perch, from the MSC were analysed for occurrence sexual abnormalities, along with a further 51 roach and 61 perch taken from the enclosed Salford Quays (Table 7.4). Histological analysis of the gonads was performed using the methodology of Jobling et al. (1998). Using an index similar to the intersex indices used in the past (EA, 1998), a measure of intersex severity (1-7) was then allocated to individual specimens, where low values indicate the presence of an ovarian cavity in testes but absence of oocytes. Values then increase in accordance with the disappearance of the sperm duct and an increase in the numbers and stage of development of the oocytes. At stage 6, over 50% of the gonad was ovarian and at stage 7, 100% of the gonad was ovarian. At this stage, intersex males and true females were distinguished by the presence/ lack of any sign of testicular tissue.

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(a) Roach Results from the MSC showed that as age increased, so did the ratio of females to males, with fish age classes of 4 onwards having, on average a male:female ratio of 1:10. This compared with a male:female ratio of 1:4 within the enclosed Quays for roach aged 5+ and older, while in both habitats, younger specimens displayed more equal ratios between sexes. Intersex gonads were observed in >50% of male roach sampled in the MSC while in the cleaner water of the Quays this was only evident in 24% of males. However, the severity of intersex did not differ significantly between the two populations (Mann Whitney U = 33.5, p=0.5) with mean index values of 2, indicating the development of an ovarian cavity, retention of sperm duct and the presence of a low number of primary oocytes. Higher index values were ascribed to a number of individuals in both populations, indicating the presence of frequent occurrence of primary and/or secondary oocytes within the testes. (b) Perch At the age of 4+, sex ratios of perch in the MSC were dominated by females with only 1 in 10 fish of this age group being male. It was not until 5+ that these females became mature and this corresponded with a sudden change to an equal sex ratio of male to females. From this point, as the year class increased, so did the sex ratio in favour of males, until at age 6+ the male: female ratio was 3:1. In contrast, the younger perch in Salford Quays were dominated by males, with females becoming predominant at a male: female ratio of 1:3 from the age of 3++. The effects of oestrogenic compounds on the perch population of the MSC was found to be extremely alarming, with 100% of all males having intersex gonads, and the severity of gonad corruption also being greater than those observed in either of the roach populations previously examined. In addition to the contrasting sex ratios observed between the two habitats, the 26 male perch sampled from Salford Quays displayed no evidence of intersex. Table 7.4 Intersex incidence and mean intersex index score for male roach and perch in the MSC and Salford Quays.

Sample size No. females No. males % Intersex males Mean male intersex index (± SD)

Roach MSC

97 54 24 54

Salford Quays

Perch MSC

Salford Quays

45 29 14 24

45 22 10 100

66 37 26 0

2.6 (± 2.5)

0

1.9 (± 1.5) 1.7 (± 1)

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(c) Ecological significance While the natural recruitment (albeit limited) of both roach and perch has been observed in both the MSC and Salford Quays, previous studies have demonstrated that sperm quality, quantity and fertilisation success in roach, are all negatively correlated with increasing degree of feminisation. In severely intersex roach, sperm motility has been shown to be reduced by up to 50%, with fertilization success reduced by up to 75% when compared with less severely intersex, or unaffected, fish (Jobling et al. 2002). Although background levels of contamination within Salford Quays are clearly high enough to have a feminising effect on roach, it is not clear whether these contaminants originate from organic sewage effluent which was trapped within the sediments prior to the isolation of the Quays or whether other compounds known to be oestrogen mimics, such as phenolic compounds are responsible. Regardless of pinpointing the exact or combined causes, it appears that perch are less susceptible to the effects of lower levels of these contaminants. However, when contamination levels are increased, as in the MSC, perch show elevated sensitivity over roach to the effects with 100% of males becoming compromised to some degree in their reproductive capacity. Although sex ratios in coarse fish populations are known to fluctuate naturally (Jamet, 1993), it is currently unknown whether oestrogenic compounds or other water quality parameters may influence skewed sex ratios in the MSC and Salford Quays. Clearly a male: female sex ratio of 1:10 in perch, with every male suffering some degree of gonad corruption is not an efficient scenario in favour of production and population sustainability. It has already been flagged that this phenomenon may have chronic impacts on the sustainability of fish populations (Gross-Sorokin et al., 2006). The combination of skewed sex ratios and the incidence and severity of intersex within the roach and perch populations of the upper Canal raises serious concerns about the additional fragility of these populations. Indeed the Environment Agency and the U.K. government have taken the view that the effects observed by the scientific community can be considered harmful and, together with the reasonable likelihood of population level effects, that this damage is unacceptable for the long term (Gross-Sorokin et al., 2006). However, it should be stressed that in all other respects the development of the roach and perch populations appears to be proceeding well in the upper MSC. Recruitment is obviously occurring, but it is not clear whether successful spawning occurs locally or whether young, presumably larval stage recruits are merely displaced downstream into the upper Canal. In either case, once present in all other respects the habitat appears to be very much suited to roach and perch as evidenced by the high growth rates and condition factors demonstrated. Thus it would appear, that contrary to current scientific opinion, the severe occurrence of the intersex condition in the MSC fish is apparently not restricting the development of the fish population. Although data currently available from the Mersey system are limited, it is interesting to compare the situation in respect of perch and roach, both within the Quays and the neighbouring MSC. Within Salford Quays, roach were indigenous and dominated the

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population structure until end of the 1990s. After this time the perch population exploded with this species becoming more and more dominant, apparently at the expense of the roach population. In contrast, despite the success and overall dominance of gudgeon in the MSC, roach and perch numbers have been maintained in equal proportions. The fact that perch demonstrate high incidents of intersex in the MSC, but are unaffected in the Quays raises the question: are the roach in Salford Quays struggling to maintain a population due to the prevalence of intersex males, with perch capitalising on increased spawning success? There could be many reasons for this observed shift in species composition within the Quays. The availability of suitable spawning substrate is another likely cause, but, nevertheless, the upper MSC and Salford Quays offer a superb model environment in which to further investigate the ecological consequences of endocrine disrupting substances on fish population dynamics.

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8.0 THE RETURN OF SALMON TO THE MERSEY Despite anecdotal evidence from anglers that salmon had been observed jumping weirs on the lower Mersey and the River Bollin, it was not until November 2001 that the first adult salmon was trapped by Agency staff at Woolston Weir near Warrington. This was proof that, for the first time since the Industrial Revolution, this species was present once again. Since the initial capture, the trap at Woolston Weir has been operated for limited periods during the autumn, and to date, 71 adults have been briefly intercepted and examined as they made their way upstream. At this stage, it is not clear whether these fish were homing to their natal river or were strays from known salmon rivers to the South (e.g. Dee) or North (e.g. Ribble). In 2005 the first juveniles were recorded, when three parr were captured on the River Goyt. Although this discovery has confirmed that under favourable water quality conditions, adults can traverse the 8km of MSC dividing the Mersey, spawn successfully and produce healthy parr, it is still unknown whether smolts can tolerate conditions during late spring on their journey to sea. Examination of the temporal records of fish trapped in October-November, reveals a clear association between numbers of migrating salmon and elevated river discharge. This is a typical cue for migratory species with increases in flow commonly triggering the migratory response. On entering the MSC, elevated flows will also enhance water quality promoting better mixing of the water column and reducing or eliminating zones of oxygen deficiency. From data currently available, it is not possible to assess the annual migratory pattern of salmon on the Mersey (Fig 8a), although adults may migrate into rivers during spring and early summer, autumn freshets also tend to move fish on that have been residing downstream of potential spawning areas. However, the general tendency in salmon populations over the last three decades has been to move towards Autumn running salmon (single sea winter fish – 1SW) rather than Spring salmon (multiple sea winter – MSW). In order to assess the true numbers and the seasonality of the migration it will be necessary to run the trap on a more frequent, either continually or at least bi-weekly sub-sampling. However, as an initial guide to the likely shape of the Mersey run, data have kindly been made available by Dee Stock assessment Programme, for the adjacent River Dee (Fig 8b), where an automatic counter operates throughout the year (Richard Cove Pers comm.) The Environment Agency have undertaken radio telemetry studies on some fish caught at Woolston Weir, although at the time of writing, no reports were available.

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Salmon numbers trapped at Woolston Weir (all data 2001-2006 combined)

No.

60 40 20 0 J

F

M

A

M

J

J

A

S

O

N

D

Month Figure 8a: Number of adult salmon trapped at Woolston Weir during 2005-2006. Note. The Woolston trap has only been operated during the months of October and November

% of total run

Seasonal proportion (%) of u/s migrating salmon on the River Dee (all data 19912006 combined) 50 40 30 20 10 0 J

F

M

A

M

J

J

A

S

O

N

D

Month Figure 8b: Seasonal proportion of upstream migrating salmon on the River Dee. 1991-2006 data combined. Data from continuously operated fish counter. Results from the Dee would suggest that either 1) larger numbers of salmon are entering the MSC during the summer months when water quality parameters are less favourable, which would mean that the numbers of adults running the Mersey are currently being under estimated, or 2) Fish have to wait until autumn when water quality is more likely to allow successful navigation of the Canal in order to reach

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potential spawning grounds in the upper catchment. Where water quality conditions are seasonally more favourable at some times than others, the timing of the run alone could govern the success/failure of the population. It is therefore of critical importance to assess the annual temporal distribution of the Mersey run in order to identify peak periods of vulnerability, where migrating adults may be at high risk from perturbations in water quality. More frequent trap operation is probably the most appropriate technique to use, throughout the spring, summer and autumn months, and potentially early winter.

8.1 The potential for a future salmon fishery In order to manage the future fishery potential of the Mersey system, it is first important to understand the life history traits of the population in question. Although salmon typically spend one or more years as parr in freshwater before migrating, adults also vary their time spent at sea. By removing a scale from each adult intercepted on the Woolston trap between 20012006, Agency staff have been able to interpret how long each fish had spent in freshwater as a parr and the time spent at sea. Initial results clearly show that the vast majority of Mersey salmon migrate to sea after spending two years in the river, with the majority of adults returning to spawn as grilse after only one year at sea (1SW) (Fig 8.1a). These data need to be treated with caution, as the limited sampling window of October-November may skew these results. For comparative purposes, data for the River Dee are also provided (Fig 8.1b). Although data from the Dee show that a small number of fish spend an extra year either as parr, or at sea as MSW adults, these data accord with the Mersey population, in that both populations show a propensity to spend more than one year in freshwater and return after one year at sea as grilse.

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No. of years spent in freshwater as parr and years spent at sea of returning adults (%) (all data 2001-2006 combined) 100 freshwater

marine

80 %

60 40 20 0 1+

2+

1+ (grilse)

2+ (MSW)

Figure 8.1a: Life history data from all adult salmon caught on the Mersey at Woolston Weir No. of years spent in freshwater as parr and years spent at sea of returning adults (%) on the River Dee (all data 1991-2006 combined)

100

marine

freshwater 80

%

60 40 20 0 1+

2+

3+

1+ 2+ 3+ (grilse) (MSW) (MSW) Figure 8.1b: Life history data from all adult salmon caught in the River Dee.1991-2006 data combined.

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8.1.1 River Bollin The River Bollin has previously been highlighted as potentially the most important part of the Mersey catchment, for the re-establishment of both anadromous and catadromous migrant populations (APEM, 2004). Salmon, sea trout, lamprey sp. and eels are all expected to have flourished within this river historically. With the gradual cleansing of the Mersey Estuary, these species are present once again and have been captured at Woolston Weir on the Lower Mersey. Although salmon are known to have traversed the MSC and succeeded in spawning in the River Goyt, less arduous journeys across the Canal are being thwarted by a number of obstructions in the River Bollin, which currently deny the access of migrants to spawning and rearing habitats. To date, mitigation efforts have not been implemented despite the recognition that salmon are now regularly observed in autumn attempting to jump Heatley Weir and gain access to the Bollin (Environment Agency web site). Comprehensive walkover surveys of the available habitat within this system have been carried out (APEM 763, 2004) and have identified a total of 12 impassable structures, which if absent or made passable would open up a total of 97,525 m2 of suitable juvenile salmonid rearing habitat and a further 5,600 m2 of spawning habitat (Table 8.1).

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Table 8.1 Summary of obstacles and cumulative increments of spawning and nursery habitats for salmon beyond each obstruction. Habitat categories based on Table 5.4 Obstacle No.

Obstacle

0 1 2

MSC Heatley Weir Little Bollington Crump Weir Styal Weir Wilmslow Weir (church) Wilmslow Crump Weir Wilmslow Park Weir Wilmslow Park Large Weir Prestbury Park Weirs Prestbury Village Weir Dale Brow Weir Stanneylands Crump Weir Deanwater Hotel Weir

3 4 5 6 7 8 9 10 11 12

MSC to Heatley Weir Heatley Weir to Little Bollington Crump Weir Little Bollington Crump Weir to Styal Weir

Cumulative Spawning Area (m2) 0 0 1,298

Cumulative Parr Area Parr + Mixed Juvenile (m2) 1,914 5,882 44,034

26 30

Styal Weir to Wilmslow Weir Wilmslow Weir to Wilmslow Crump Weir

1,575 1,575

46,854 48,585

31

Wilmslow Crump Weir to Wilmslow Park Weir

1,575

49,214

32

Wilmslow Park Weir to Wilmslow Park Large Weir

1,606

49,893

40

Wilmslow Park Large Weir to Prestbury Park Weirs

1,726

66,515

41

Prestbury Park Weirs to Prestbury Village Weir

1,750

67,974

42

Prestbury Village Weir to Dale Brow Weir

1,958

70,392

47 52

Dale Brow Weir to Macclesfield Weir on Bollin Stanneylands Crump Weir to Deanwater Hotel Weir

2,659 3,963

80,449 85,839

59

Deanwater Hotel Weir to Brrok House Weir on Dean

5,600

97,525

Distance From MSC (km) 0 3 7

Stretch of Bollin/Dean opened up

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Cost benefit analysis (APEM, 2003) has revealed that providing fish passes around the first two weirs (as far as Styal Weir), would be the minimum requirement to create a self sustaining population. This would provide migrating adult salmon with 44,034 m2 of suitable parr/mixed juvenile habitat. Based on Environment Agency’s National Fisheries Classification Scheme (NRA, 1994), the lower Bollin has been graded on the border of categories D and E. This provides a realistic and attainable estimate of a population density of 9 fry/100m2 and 3 parr/100m2. Using these figures to model the impact of adults overcoming the first two obstacles and navigating the river as far a Styal Weir, predicts the Summer standing crop of salmon parr for the River Bollin between Styal Weir and the MSC at a figure of 1321. Engineering access to the lower Bollin in such a way would also provide a good deal (23%) of the entire river’s available habitat suitable for salmonid spawning. Above Styal Weir, little spawning habitat exists until a further 26 km and 8 obstructions have been navigated. Beyond this, successful navigation of a further two obstacles on the River Dean would facilitate a further 54% of the total available spawning habitat of the entire system. This is indicative of the potential importance of the River Dean for the production of salmonids prior to industrialisation and river engineering and its likely historical contribution to the Mersey catchment as a whole. Despite the availability of suitable sized spawning media in the lower Bollin, this has been found to contain high levels of fine sediments. In order to maximise incubation and hatching success, such habitats would benefit from an annual cleaning programme by jet washing. The spawning habitat requirements of lamprey are similar to salmon so the ability to access these areas would benefit these species equally. In addition, larval habitats for lamprey are plentiful in the Bollin, with an abundance of silt margins in which ammocoetes could burrow. Impact of barriers on coarse fish populations in the River Bollin The relatively fast flowing nature of the River Bollin also lends itself well to the sustainability of coarse fish species. In particular those species within the rheophilic guild (Balon, 1975, 1981; Mann, 1996), such as dace, barbel and chub. Dace and barbel in particular are known to undertake pre- and post- spawning migrations (Clough & Ladle, 1997; Lucas & Frear, 1997) and the removal of, or provision of means of by-passing these barriers is likely to also be of benefit to these populations. Other migratory species such as trout and lamprey would also benefit, although eels, should they return to the system are unlikely to be hindered significantly by such barriers as upstream migrating elvers are capable of traversing around the wet walls of weir structures above the water level. Water Quality On examination of water quality data parameters available for the Bollin at Heatley Mill, it is apparent that neither the success of cyprinids or salmonids should be compromised by the water quality in the lower River Bollin. Long term trends in

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Ammonia show a dramatic decline, with current levels well below the imperative standards for both cyprinids and salmonids. Indeed, over the last two years, ammonia levels have only exceeded the guideline standards of 0.2 mg/l in three of the 24 months where measurements were taken. Dissolved oxygen also exceeds the standards set out for salmonid fisheries and the vast majority of monthly BOD levels over the last two years also conform to salmonid fishery status, with all BOD measurements being well within the limits for cyprinids. 8.1.2 The River Goyt Probably the least environmentally stressed river under consideration in this review, the Goyt begins its course on the Derbyshire moors between Buxton and Macclesfield and feeds Errwood and Fernilee reservoirs before making its way to Stockport where it meets the River Tame and becomes the Mersey. In the upper reaches the Goyt supports a thriving brown trout fishery, with good quality spawning habitat available in the many tributary streams. Below the reservoirs the Goyt benefits from compensation discharge from Fernilee reservoir, thus maintaining a healthy flow and supports a mixed salmonid and coarse fishery. In the lower reaches, between Marple and Stockport the river is regarded as a quality coarse fishery, with an abundance of large chub and Barbel. Despite the occurrence of some juvenile fish it appears that there may be factors limiting natural recruitment, with the fishery’s reputation relying heavily on stocking practices. Undoubtedly the most significant discovery on the River Goyt and indeed the entire system, was the capture of four 0+ salmon parr near Stockport Town Centre during 2005. For the first time since the industrial revolution, this proves the potential of the Mersey system to support migratory fish stocks once again. This is particularly remarkable because to reach the River Goyt, spawning adults must first navigate the 8 Km of lacustrine channel of the MSC from Rixton Junction before picking up the course of the upper Mersey at Irlam. More remarkable still would be if downstream migrating smolts were capable of tolerating such poor conditions, during a particularly vulnerable period in their life history, in May when water quality conditions are likely to be poor. Only if this phase of the migration pattern is fulfilled, will a self sustaining population of salmon be achievable in the Mersey. Water Quality Long term data sets have been not available in order to establish long term trends in the status of the water quality of the River Goyt. However, recent data over the last two years, suggest that water quality of the Goyt is currently capable of supporting a salmonid fishery, with BOD, DO and ammonia well within target levels throughout the year. Physical habitat and obstructions The River Goyt is not without its problems. Although the installation of a fish pass on the Mersey at Northenden has facilitated a migratory pathway to access the river, the Goyt itself has a further 15 structures which are classified as impassable under Q90 conditions. In addition, there are further cross-river structures for fish to navigate,

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although these are considered to be passable under most conditions, being categorised as grade 2 and 3 obstructions, such minor structures have been identified as being potentially problematic to successful migration to spawning areas (Lucas & Frear, 1997). Overcoming obstructions to allow the passage of migratory species would provide a good deal of quality rearing habitat for salmonids within this river. A walkover habitat study of the river (APEM, 2006) revealed that the Goyt could provide 170,288 m2 of suitable rearing habitat for young salmon throughout their juvenile riverine phase, with a further 1,811m2 of potential spawning habitat, the latter being sufficient to accommodate over 190 spawning pairs of salmon. In general, the rheophilic spawning habitat required by both salmonids and some coarse fish species, such as dace and barbel, is considered as poor in the Goyt. This is due to excessive siltation problems. This was particularly evident in the lower Goyt reaches in 2006, when a fine layer of silt and algae covered potential suitable substrates (APEM, 2006). It is worth considering the benefits of a gravel-washing programme in the future in order to enhance spawning success and egg survival of both salmonids and cyprinids of the rheophilic guild. Access from the Goyt into its tributaries, the River Sett and Black Brook should not be regarded as high priority, due to the relatively low abundance of suitable habitat for both spawning and rearing of salmonids in these streams.

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9.0 FACTORS CURRENTLY AFFECTING THE SUCCESS OF COARSE FISH SPECIES 9.1 Limnophilic species In accordance with Huet’s zonation model, limnophilic cyprinids are not well suited to the higher flow characteristics of the upper catchment and prefer deeper, slow flowing, lowland habitats. Focus on these species is therefore centred on the Lower River Irwell, the MSC and Salford Quays. Should EC FFD water quality targets be achieved, in tandem with the provision of appropriate physical habitat structure, the MSC and Salford Quays could potentially support the following species: roach, rudd, common bream, silver bream, common carp, tench, perch and pike. In addition, gudgeon would be supported throughout the MSC, as indeed they are present in the Turning Basin area. Because of contrasting water quality between those areas that currently do and do not benefit from amelioration measures, factors constraining limnopils will be considered for each of these areas in turn. In considering the lower River Irwell and the MSC, the water quality data presented within this report (and in greater detail in (APEM, 2007)) clearly indicate that DO and ammonia levels are not currently meeting EC FFD target levels for cyprinids. These data also provide information regarding the seasonality of water quality issues and also fine scale detail of the diel cyclic pattern of oxygen availability. Because of the limited availability of oxygen within these habitats, fish populations are seasonally constrained by the areas of the Canal they can exploit, with both longitudinal and vertical ranges becoming minimal during the summer months. According to an extensive search of the relevant literature, hypoxic condition can affect fish in many ways, - including increased susceptibility to pollution, growth, reproductive capacity and ability to avoid predation. Although growth rates and condition factors of the adult stock remain favourable, this may be due to low levels of fish density currently present. Should stock density increase then the health of these populations is likely to be put under greater pressure with food availability becoming limited within the areas of the Canal that the fish are able to tolerate. As mentioned above, being subject to inadequate oxygen levels, the sustained swimming capability of fish is also compromised, making them more vulnerable to predation. In addition, predation risk is likely to be further elevated by the effective ‘herding’ of fish shoals within areas of acceptable water quality. This may be manifested as either vertical redistribution of the population to the surface layers or towards confined areas where oxygen levels are more favourable such as downstream of weirs. Where this happens fish are likely to be at greater risk from avian predators, such as cormorants, which frequent the Canal. Vertical habitat shifts by adult fish may also be impacting directly on the survival of 0+ fishes. This is reported to shift trophic interactions, with benthic invertebrates becoming inaccessible, larval fishes occupying the upper littoral zones become a more viable food resource for adult fishes.

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The oxygen levels currently observed in these habitats are brought about by a combination of chemical, biological and physical factors. Although reducing sewage inputs will benefit the aquatic ecosystem in many ways, it alone will not combat the combination of the physical structure of the Canal, the historic deposition of organic sediments and the lack of physical mixing which causes the system to stratify. Sewage effluents are also clearly affecting fish populations within the MSC as a consequence of endocrine disruption. Although the direct ecological relevance of these impacts is not clearly understood at present, improvement in inputs and associated oestrogenic compounds are likely to maintain a more balanced sex ratio, increase male fertility and may ultimately increase reproductive success. This may also potentially show immediate benefits to the survival of successfully fertilised fish eggs. Limnophilic cyprinid eggs are no more tolerant to the affects of ‘sewage fungus’, as they are deposited in areas with little or no flow to refresh them. Exposure to such bacteria may play a very important role in influencing the survival of embryonic and larval stages of development. However, as stated earlier, colonisation of the upper MSC with coarse fish has already successfully occurred, with excellent growth and condition. Whether recruitment is constrained by sex reversal requires more detailed investigation. Other major factors threatening the fish of the upper MSC and lower Irwell include the immediate effects of episodic input from storm overflows, resulting in mass mortalities from the effects of organic pollution. The lack of appropriate ‘off river’ sanctuaries from floods is also a major issue potentially retarding recruitment in this area of the catchment. This is a potentially critical area for the future development of coarse fish populations within the MSC, and indeed is the central area of investigation in this study. However, it should be recognised that the physical structure of the MSC – with effectively impassable pounds between locks (i.e. Mode Wheel to Barton, Barton to Irlam and possibly from Bollin Point to Latchford Locks) prevents fish movement away from areas of deteriorating water quality. This issue is of great significance, as was seen with the substantial fish kill that occurred in May 2006, when low oxygen concentrations in the Mode Wheel to Barton pound resulted in the death of several thousand fish. Despite similar water quality conditions in the Turning Basin, relatively few dead fish were observed, indicating that most of the fish previously present (from APEM/EA sonar surveys) had apparently moved upstream towards the Irwell where channel morphology affords a degree of vertical mixing and hence maintains higher oxygen levels. With the lower pounds the option for fish to move to more favourable conditions is either absent or extremely limited, hence the observed mortality. Ironically, with the success of the water quality improvements, fish have been encouraged to colonise these areas, but unwittingly, are then trapped with no avenue to escape during the episodic, poor water quality events. 9.1.1Oxygenated areas The oxygenation programme was primarily initiated to improve the aesthetic value of the upper MSC. In addition to achieving these goals, these areas extend the spatial habitat available to fish populations throughout the summer and during periods of hypoxia, offer an alternative refuge from the oxygenated water below Adelphi Weir.

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Despite these benefits the artificial injection of oxygen to the Canal currently offers little more than a temporary life support system to individuals, with little benefit at the longer-term population level. This is primarily due to physical habitat constraints within these areas, which if rectified could prove highly beneficial to the selfsustainability of limnophils within the Canal. With the spawning of limnophils typically occurring between May and July, the availability of appropriate habitats within areas where oxygen levels can be maintained are extremely limited, with nocturnal oxygen sags at this time of year resulting in complete depletion of oxygen in the surface layers throughout the majority of the Canal’s entire length. Ideally the provision of a littoral shelf 2-3 metres wide with a mean depth of 1m would encourage the colonisation of macrophytes and the associated communities of macro invertebrates and zooplankton. In turn these habitats would provide ideal nursery habitats with appropriate food supplies for larval fish and because oxygen levels are maintained at desirable levels, the provision of appropriate spawning media would increase egg survival. The creation of such habitats throughout the rest of the upper Canal would also be of great benefit to fish recruitment. The softer bank engineering elsewhere, may facilitate the creation of such habitats, more easily than in the sheer banked areas of the Canal, which currently benefit from oxygen supplementation.

9.2 Salford Quays Within Salford Quays fish populations depend on the maintenance of oxygen levels via ‘Helixor’ mixers. This alleviates the immediate problems arising from low DO levels, thus highlighting the physical factors that are currently affecting the fish populations. In effect this provides an insight into the future regarding the future for fish populations in the MSC, once water quality problems have been resolved. The key physical issue within the Quays is a lack of littoral habitats, which are needed to provide macrophytes for spawning, a sanctuary from predation and the provision of zooplankton production on which larval fish can feed. On hatching, limnophils are poorly developed and rely on yolk reserves in order to gain enough energy to swim to the surface and fill their swim bladder. Until this point, ‘free embryos’ have negative buoyancy and in the absence of macrophytes to support them, will fall to the sediment where cutaneous respiration has to be maintained until enough energy has been absorbed from the yolk to make the journey to the surface. In order to cope with such conditions, some species such as pike have developed adhesive cement glands, upon hatching, with which they attach themselves to macrophytes to avoid sinking to the lower anoxic layers (Braum et al., 1996). With the shear nature of the banks within the Quays and mean depths of 7 metres, the lack of such marginal habitats is likely to be a key issue retarding the natural recruitment of roach and perch while apparently, severely limiting the recruitment of bream, carp, rudd and tench. Although there is still evidence of endocrine disruption in the roach population of the Quays, this watercourse no longer receives any sewage input and therefore any oestrogenic compounds present must have been locked into the Quays at the time of their isolation from the MSC. As the MSC sediments are similar in origin and nature, it stands to reason that endocrine disruption is likely to continue to influence the

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condition of fish within the MSC in the future, even following water quality improvements.

9.3 Rheophilic species Rheophilic species have a general requirement to be lithophilic spawners, i.e. depositing eggs either beneath or over gravel and occasionally on macrophytes in flowing water. This generally restricts spawning to the mid to upper zones of the catchment, although within healthy ecosystems the Cyprinidae in particular can utilise a whole range of habitats throughout the catchment in accordance with varying life stage and temporal physiological requirements. Typically, assuming a lack of physical barriers, rheophilic cyprinids undertake an upstream migration to their spawning grounds, thus allowing a good distance of downstream rearing habitat into which their larvae can drift and rear within suitable nursery habitats. Dace in particular are known to have extensive home ranges and often congregate in large numbers within the tidal zone of rivers (Pers. observation) with diel shifts in spatial habitat also observed (Clough & Ladle 1997). Barbel is another species which have received attention regarding their annual movement and have been recorded making upstream migrations up to 20 Km in order to reach suitable spawning grounds (Lucas & Frear, 1997; Baras et al., 1994). The presence and regularity of impassable structures within the Mersey catchment, (both physical and in the case of the MSC chemical) highlight these constraints on fish movement as a factor potentially restraining the success of these populations. In addition to movement being impeded and a restricted choice of spawning grounds being available, these populations are also subject to additional pressures. Where fish movement is confined, forcing fish to spawn below an impassable structure, with no future upstream migration occurring, these populations become vulnerable to pollution events. In the event of a fish kill, recolonisation of these communities would have to originate from upstream. There are thought to be in excess of 500 potential barriers to fish movement within the Mersey catchment. Indeed, in addition to the above, the long-term health of populations within the Mersey is also currently compromised by a lack of genetic mixing; with potentially isolated populations existing, which are vulnerable to the effects of poor genetic diversity. A detailed examination of in-stream barriers and their impacts on restricting access to habitats for both coarse fish and salmonids is thus required across the catchment. Lithophilous spawners are more specific in their habitat requirements, with a combination of appropriate water quality, velocity and substrate all critical to the survival and subsequent hatching of the eggs. Because of the direct proximity to the substrate, eggs may be at risk from industrial toxins already present within the bed sediments. Mechanical sedimentation of spawning gravels has also been reported to be an issue within the catchment, particularly in the Rivers Goyt and Bollin, with high loads of fine sediment blocking the interstitial spaces between gravel particles and thus reducing oxygen flow over the eggs. Another issue potentially retarding hatching success below Adelphi Weir is a coating of algal slime, which has been reported as covering much of the gravel substrate. This condition may only be alleviated by considerably reduced phosphate delivery from sewage treatment inputs.

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From the fish survey data available to date, chub appear to be the most spatially successful rheophillic cyprinid, although despite good numbers of adults in the River Goyt, recruitment has not been evident in this river in the last four years. There is very little evidence of naturally sustainable populations of dace throughout the catchment, including the Rivers Weaver and Gowy. This is despite extensive stocking efforts to reinstate this species. Although degraded water quality is undoubtedly unfavourable to dace, the effects of barriers to migration need to be further investigated to establish the direct relevance of this environmental component to dace stocks. Although locally sustainable populations of brown trout are evident within the upper reaches of most of the catchment, grayling recruitment appears to be sporadic. This species requires better water quality than the Cyprinidae and under current conditions it is unlikely that stocks of this species will increase naturally, except in those tributaries outside of the main conurbation. Limited recruitment of barbel has been observed to date, with individual 1+ specimens recorded from the Rivers Goyt and Bollin being the only indications of successful recruitment. In the case of the River Bollin the juvenile specimen was captured below Heatley Weir. As this structure is impassable to smaller fish, this highlights the current restriction for these species to access many miles of good quality spawning and nursery habitats further upstream. In the case of barbel it is likely that instream barriers to migration are the key factor restricting recruitment success. Within parts of the catchment, the effects of ‘sewage’fungus’ may also be a major issue influencing the survival of embryonic and larval stages of development. At present there are no data available either identifying spawning sites or quantifying survival rates of eggs of any of the species under consideration. Without these key data it is not possible to ascertain the precise factors restricting the success of rheophilous or lithophilous fishes, although it is likely to be a combination of the factors discussed. Although the lower River Irwell and MSC do not offer suitable spawning habitats for rheophilic species, this component of the catchment, under further water quality and habitat improvements, has the potential to accommodate good numbers of these species at all life stages. This is on the condition that restoration measures can be initiated in order to allow passage around weirs and other barriers to allow access to a wider range of habitats.

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10.0 FACTORS CURRENTLY AFFECTING THE SUCCESS OF MIGRATORY SPECIES 10.1 Catadromous species 10.1.1 Eel (Anguilla Anguilla) There is generally no kind of natural or artificial water body that is not inhabited by eels, provided they can reach it and find food (Tesch, 1991). Historical anecdotes record an abundance of eels in the Rivers Irwell and Irk prior to the Industrial Revolution, with the last reports of the presence of eels from Mode Wheel Lock as recently as 1907 (Corbett, 1907). Other records highlight the lower Mersey as an important eel fishery. In 1190 Liverpool was known as 'Liuerpul', meaning a pool or creek with muddy water, although other origins of the name have been suggested, including 'elverpool', a reference to the large number of eels in the lower Mersey (http://www.liverpoolcityportal.co.uk/history/history_index.html). Historical records of salmon in the upper catchment indicate that eels would not have had any problem in navigating either physical or water quality barriers and it is fair to assume that they were once an important component of the ichthyofauna of both the Irwell and upper Mersey catchments. The eel has been regarded as one of the most pollution tolerant of fish and was evident as one of the first species to take advantage of improving water quality in the Thames (Jones, 2006). Wheeler (1979) notes that even during the height of the pollution in the Thames, eels could be found in the river’s upper reaches. It is unclear whether these stocks originated naturally from the successful ascent of the river by elvers or from the substantial numbers of elvers that are now known to have been imported via the Thames, for food consumption. The reasons for the total extinction of eels from the upper Mersey catchment is not known, but the extended freshwater phase of the European eel can typically range between 7-19 years (Maitland & Campbell, 1992), making them particularly susceptible to bioaccumulation of various pollutants as well as more immediate sensitivity to poor oxygen levels during migration in either direction. Despite their avoidance of low oxygen concentrations, eels commonly occur in deep stratified water-bodies, but favour the shallower littoral zone, only venturing into deeper water for limited periods to feed (Tesch, 1991). The apparent tolerance of eels to poor water quality poses the question: of whether water quality has improved enough to support eels? The presence of salmon migrating through the MSC and the subsequent survival of salmon parr within the River Goyt would suggest that this is the case and that physical barriers are also not likely to be a significant hindrance to recolonisation, should migration through the Canal be possible. Studies of the fish populations of tributaries of the Weaver system, carried out in 2001 by the Centre for Ecology and Hydrology revealed that eels of mixed size classes dominated species composition (personal observation), Environment Agency angling records and electric fishing surveys also report eels and river lamprey in both the

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Weaver and the Gowy. This indicates that the Mersey Estuary still has a healthy input of elvers, but the upstream migration and subsequent dispersal of these fish is exclusive of the River Mersey upstream of the confluence with the MSC. A possible explanation for the continued absence of this species would be a lack of a biochemical signal emanating from these rivers. Where migratory species do not show specific homing preferences to natal streams, evidence exists to support the use of pheromonal cues provided by conspecifics to aid navigation to suitable habitats, either for spawning or rearing purposes (Baker & Hicks, 2003). Indeed Li et al. (1995) provide strong evidence that adult sea lampreys select spawning streams based on a pheromone released by upstream larval fish, which comprises unique bile acids. Briand et al. (2004) also reported the increased attraction of migrating glass eels to a fish pass where the water had been buffered with the odour of adult eels. An alternative or perhaps additional explanation, from work carried out specifically on eel species, including Anguilla anguilla, suggest that eels show a strong attraction to geosmin, a naturally produced odour originating from terrestrial and freshwater microbes. This odour is believed to play an important role in guiding the migration of elvers to suitable habitats for rearing to adulthood (Miles, 1968; Tosi& Sola, 1993). This may be more important than the odours produced by conspecifics, which Sorensen (1986) reports to be comparatively weakly attractive. Thus there appear to be several possible explanations for the failure of eels to have recolonised the upper Mersey: 1) naturally produced odours are not present in the upper Mersey, 2) such odours are present but are being masked by the water chemistry of the MSC, 3) there is a lack of pheromone signal from conspecifics, 4) any combination of these factors. There is clearly substantial scope for an experimental approach towards the reintroduction of this species to the catchment. 10.1.2 Flounder (Platichthys flesus) Although primarily considered as a marine species, the European flounder is also classified as catadromous, often migrating large distances into freshwater. Prior to the construction of the MSC, it is likely that the distribution of this species would have extended into freshwater, ahead of the estuary, within which it is confined today. Unlike the eel, freshwater habitats are not essential for flounders to complete their life cycle. Therefore, unless water quality, habitat and feeding conditions are good, there is little incentive or benefit to this species in migrating upstream. It is therefore unlikely that this species will complement the fish community structure of the MSC and its tributaries in the foreseeable future.

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10.2 Anadromous species 10.2.1 Atlantic salmon (Salmo salar) The fact that salmon are already attempting to make a natural comeback to the Mersey system is of immense encouragement and confirmation that future investment in the continued improvement of water quality will show ecological rewards. Suitability of the catchment in terms of water quality, availability of suitable habitats and barriers to migration must still be regarded as poor. However, sensitive management of these issues would dramatically increase the successful development of a sustainable salmon population. A primary consideration is the seasonality of migration patterns and use of various habitats by different life stages. Adult fish typically migrate into freshwater between February and November, depending on how many years the adults have spent at sea. It is quite possible though that successful migration into the MSC and beyond can only be achieved later in the Autumn, when increased flow, lower water temperatures and elevated oxygen levels facilitate the navigation of the MSC. Following passage to the rivers, adults need to locate suitable spawning gravels in which to deposit their eggs in late December/early January, and suitable rearing habitats for the juveniles also need to be available. Current access to these habitats is heavily compromised by the presence of instream barriers to migration, such as weirs. The consequence of barriers to migration and the potential for salmon production by providing a means for salmon to bypass such structures was examined in detail for the River Bollin (APEM, 2004). These results are summarised in chapter 8 of the current report, in relation to their relevance to the Mersey catchment generally. It is also important that, following successful navigation to sites with suitable physical habitat, water quality must be of a high enough standard and stability to allow successful incubation and hatching of eggs and the subsequent survival of parr. The presence of 4 salmon parr in the River Goyt in 2005 demonstrates that the river is capable of producing healthy juvenile salmon. However, in order to complete their life cycle, smoltification must occur, followed by successful migration back to the marine environment. During smoltification salmon undergo both a physical and morphological transformation, which exerts major stresses on the individual, thus making this life stage particularly sensitive to perturbations in water quality. This is perhaps the most critical phase in the completion of the life cycle, and whether Mersey smolts are capable of surviving the water quality of the MSC on their seaward journey is a key issue, which needs to be answered. The smolt run on neighbouring rivers (Dee and Ribble) typically takes place in May, when river flows can be low and water quality poor, as was seen in the MSC fish kill in May 2006. With rising water temperatures also increasing the risk of stratification and hypoxic/anoxic conditions at this time of year, it may be that Mersey salmon would benefit from adapting an alternative migration strategy (autumn) in order to succeed in re-establishing a self sustaining population in the catchment. Indeed, it has recently been highlighted that in some rivers a significant proportion of the juvenile salmon population begin their

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seaward migration as parr during the autumn (Pinder et al., 2007). Although not capable of tolerating saline conditions, these fish continue to develop in the upper estuary prior to becoming smolts and continuing their journey. The premature migration of Mersey parr could be beneficial in enabling the negotiation of the MSC when both water quality and individual physiological fragility are more favourable. Obviously more detailed work is required on this important issue. 10.2.2 Sea trout (Salmo trutta) The presence of natural populations of brown trout in headwater streams of the system suggest that a proportion of these individuals would be likely to become successful migrants, should this be a viable option. It is quite likely that some juveniles do undergo smoltification and set off in a seaward direction but whether or not this does occur and whether individuals are able to tolerate water quality parameters on their outward journey is not currently known. It is without doubt though, that any returning adults are going to be restricted in their upstream passage by current instream barriers, thus making the return journey to their natal streams impossible. In addition, adult sea trout peak migration period is in the summer months during the worst water quality conditions in the Canal. Indeed sea trout have been observed in distress during low oxygen conditions in the Mersey estuary around Runcorn (Hendry, pers obs.) Future fish surveys should therefore aim to identify whether or not smoltification occurs in these populations. If it does, these individuals are probably presently lost from the population. Water quality improvements and the provision of fish passes could potentially boost trout stocks as well as benefiting salmon. 10.2.3 River and sea lamprey (Lampetra fluviatilis and Petromyzon marinus) The water quality requirements of lamprey species are not dissimilar to that of salmonids. However, the timing of immigration and emigration periods do differ between the two families and between the two lamprey species, which may have implications for the seasonal effects of poor water quality on migration success. While the upstream migration of sea lamprey peaks during May and June, river lamprey enter rivers during late Summer to Autumn. Downstream migration of metamorphosed sea lamprey typically takes place in May and June, with river lamprey remaining in their natal rivers until late Winter to early Summer. Clearly, where migration occurs during periods of warm weather and low flows, the challenges posed by poor water quality will increase. While parallels can also be drawn between the habitat requirements of adult salmonids and lampreys, with good quality, clean gravels required to facilitate successful spawning, the habitat requirements of early life history stages differ markedly. The larval life stages of lamprey (ammocoetes) are sedentary, where individuals remain in burrows within the silt for several years until metamorphosis occurs. The preferred silt habitats do not contain high organic content hence, the, sediment within the MSC is unlikely to provide a suitable habitat for lamprey ammocoetes to develop, regardless of the presence of additional toxins. Suitable spawning and rearing habitats are therefore likely to be restricted to the tributary rivers such as the Bollin, Mersey and Irwell. However, at present, no data on habitat availability are available for these protected species.

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A major factor retarding the recolonisation of lamprey populations could be the lack of pheromone signal (Li et al., 1995) from the upper Mersey Rivers. Like the eel, river lamprey commonly occur in the Weaver and Gowy systems, indicating a preference for these rivers, over the Bollin and those rivers feeding the MSC. Assuming water quality parameters and habitat availability are similar between the Weaver and the Bollin, this provides scope for experimental reintroductions and monitoring to take place to establish the viability of an extended restocking programme to the rivers of the upper Mersey drainage.

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11.0 THE INFLUENCE OF THE MSC ON THE RECOVERY OF FISH POPULATIONS THROUGHOUT THE MERSEY BASIN Despite significant improvements in the water quality of the peripheral rivers of the Mersey catchment, and to some extent in the MSC itself, the physical nature of the MSC, in its current state, will always restrict the recovery of fish populations for a variety of reasons. This final section of the report focuses directly on the influence of the MSC on the current status and the future recovery of the Mersey Basin fisheries.

11.1 Physical Nature of the MSC The MSC extends for approximately 35 miles from Salford Quays to Easton and is classified as a Heavily Modified Waterbody. Designed with scant regard for the future environmental demands of the catchment, the canal was constructed to serve its purpose as a major navigation route between the Mersey Estuary and the Manchester conurbation. Consequently, all of the rivers of the upper catchment, including the Mersey and the Irwell have been severely impacted by their effective isolation from their estuary, by a combination of intrinsically linked chemical and physical factors. The key physical factor in the design of the Canal is the sheer volume of the water body, particularly the depth, which typically varies between 5 and 9 metres. This alone is directly responsible for the lacustrine nature of the Canal, which has direct implications for the transport of pollutants, while severely compromising scope for the natural oxygenation throughout the system. The homogeneity of in-stream habitat types, such as a lack of macrophytes and shallow margins also seriously limits the value of the MSC as a sustainable fishery in its own right.

11.2 Water Quality Issues The key parameters impacting on the ecological health of the MSC have been highlighted as BOD, DO, pH and ammonia. Although the water chemistry of the Lower River Irwell is not dissimilar, the shallower nature of this water body promotes higher velocities and reoxygenation, while decreasing the retention time of pollutants, and consequently, with the exception of ammonia, the water quality of the Irwell now conforms to EC FFD targets for both BOD and DO for much of the time. However, on entering the upper MSC, water velocities can be non-detectable, resulting in reduced particulate carrying capacity and consequently the upper Canal acts as a settlement sump, where the historical accumulation of contaminants within the substrate exert high levels of BOD and a subsequent propensity for the water to stratify, promoting anoxic conditions. Although a continuous trend in water quality improvements is evident, both in the tributary rivers and the Canal, the eradication of any future pollutants from the tributaries may not alleviate the rise of anoxia, based on the depth of the canal and the historic accumulation of organic sediments. This highlights the constraints on future water quality improvements by the physical morphology of the MSC. Indeed in a parallel study conducted by APEM, reviewing the water quality of the MSC (APEM, 410039), analysis of historical data, show only

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minor improvements in DO over the last 20 years. Further to this, each pounded stretch of the Canal below Mode Wheel Locks has repeatedly failed to achieve concentrations of dissolved oxygen greater than the standard of 4 mg/l which is required for compliance with the EC FFD to support a cyprinid fishery. Although sonar surveys provide evidence that fish populations do exist within the MSC, the Canal itself is not capable of supporting fish on a permanent basis and in particular fails to accommodate the spawning requirements of adults and the ecological demands of the more vulnerable early life history stages. Consequently the Canal is a volatile ‘knife edge’ habitat for fish and subject to both extended periods of poor water quality, and more sudden ‘episodic’ events, such as discharges from combined sewer overflows during periods of wet weather and low oxygen stratified periods during quiescent weather. These events often result in a rapid deterioration in water quality and where fish are unable to move into areas of acceptable water quality, are likely to be disastrous, resulting in extensive fish mortalities.

11.3 Eutrophication Ironically, the continued improvements in pollution input which have promoted improved water clarity in recent years gives rise to additional problems previously not experienced in the Canal. The combination of the historical accumulation of phosphate within the substrate, the continuous delivery of nutrients from WwTW effluent and increased light penetration, all increase the risk of severe algal blooms and hyper-eutrophic conditions. The production of such blooms can have a dramatic effect on fish populations by causing severe oxygen sags during darkness, contrasted by the super saturation of oxygen levels during daylight. In addition to the stress caused to fish by low levels of DO, excessive algal growth promotes a rise in pH to harmful levels while also increasing the toxicity of ammonia, by increasing the concentration of unionised ammonia (NH3). This is believed to have been the cause of a major fish kill, in the pound between Mode Wheel and Barton Locks in May 2006.

11.4 Endocrine Disruption The occurrence of intersex and the severity of feminisation is known to be positively correlated with the proportion of treated sewage effluent in receiving waters (GrossSorokin et al., 2006). Although the ecological impacts of this phenomenon on the fish populations of the MSC are not presently understood, due to the human population density of the upper catchment, during periods of low flow, the proportion of flow in the Irwell that has not passed through sewage treatment works has been estimated at less than 10 percent. With an ever growing population it is clear that the effects of feminisation on fish in the MSC is a permanent issue and under current sewage treatment methods is not likely to improve in the future.

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11.5 Physical barriers and impoundment of stocks Although the MSC upstream of Rixton Junction severely compromises the migration of fish, due to water quality characteristics, the MSC between Rixton Junction and the River Irwell is also physically impounded by lock gates at Mode Wheel, Barton and Irlam. This not only causes serious problems to all fishes which either depend on or benefit from an open migration route between the estuary and the upper catchment, but with these barriers only being passable on an infrequent basis, also holds serious implications for the entrapment of fish in confined areas. Where water quality deteriorates due to anoxia, algal production or pollution input from ‘point source’ the inability of fish to migrate to areas of acceptable water quality is likely to result in large scale fish kills.

11.6 Additional impacts on migration and consequences Throughout the Mersey catchment, in-stream barriers, such as weirs, seriously restrict the spatial mobility of stocks. The combination of poor water quality and physical obstructions in the MSC suggest that the movement of coarse fish stocks between the Rivers Bollin, upper Mersey and Irwell is unlikely to occur on a frequent basis. With the ever present threats of fish kills from various sources or processes, this not only compromises the natural recolonisation of pollution impacted areas, but will also reduce, or in some cases may eliminate genetic mixing, leaving isolated populations vulnerable to a range of environmental conditions. The influence of the lack of flow is also likely to impact on successful migration, as river discharge often acts as an important cue for the timing of either upstream or downstream migration. Where fish are unable to detect the direction of flow, this may also cause disorientation. However, this said, little evidence exists to suggest that the impacts of anthropogenic lacustrine habitats on river systems in northern England and Scotland have a serious impact on upstream migration, with Atlantic salmon often negotiating a number of lakes, reservoirs or lochs before reaching their spawning grounds.

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12.0 ANALYSIS OF POTENTIAL FISH REFUGE AREAS DURING POLLUTION EVENTS USING AERIAL PHOTOGRAPHY

12.1 Introduction As discussed in APEM 2007 periods of sustained heavy rain within the Irwell catchment cause storage tanks to overflow in a combined sewage overflow (CSO) spill, discharging sewage directly into the Canal (Plate 12.1 shows a typical flow out of Davyhulme WwTW). The environmental implications of this type of discharge can have numerous negative impacts, including oxygen crashes which ultimately lead to fish kills. In fast flowing rivers the impact is lessened as the polluted water is flushed through the system quicker. However, the canalised nature of the MSC means that water can be retained and impounded for a number of days between the locks posing threats to all aquatic life. This threat means that the fish populations would need to migrate to safe areas (refuges), to avoid death.

Plate 12.1. Discharge outflow from Davyhulme water treatment works As part of the MSC investigation, an aerial photography survey was undertaken taken by APEM to identify potential refuge areas along the stretch of the MSC between Mode Wheel Locks and Latchford Locks. Upstream of Mode Wheel locks, potential fish kills and the associated need for refuge is considered to be low as fish can escape up the River Irwell. Furthermore the Turning Basin at Salford Quays is artificially oxygenated throughout the typically drier hotter months of the summer (May – September) sustaining reasonable oxygen levels, reducing the potential for fish kills and need for refuge. Downstream of Mode Wheel there is no oxygenation to maintain reasonable levels of water quality, and as such fish kills can be common in the summer months. For example in May 2006, APEM attended a substantial fish kill incident that occurred between Mode Wheel and Barton locks, where thousands of coarse fish died. This incident clearly highlighted the need for refuge for fish during pollution incidents. Hence the purpose of this section therefore is to focus on the MSC

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downstream of Mode Wheel, where areas for fish to escape from stressful environmental conditions are required. Aerial imagery in conjunction with a ground level inspection of the MSC (by boat) were compiled into GIS software to determine potential locations of fish refuges within the three pounds identified; Mode Wheel locks to Barton locks, Barton locks to Irlam locks and Irlam locks to Latchford locks. While more detailed analysis will be discussed in the final reporting stage of this investigation, initial findings are discussed below.

12.2 Mode Wheel locks to Barton locks (approx 5.5km) This stretch of the MSC is the most industrial reach of the Canal under investigation, running through Trafford Park, the residential areas of Eccles and derelict land before reaching the UU water treatment facilities at Davyhulme and Barton Locks. Interrogation of the aerial photography and ground survey showed that there were no naturally flowing streams in this stretch that could provide natural refuge for fish. As such fish are totally enclosed between the lock gates and have no ‘escape route’ away from deoxygenated water. However it is worth noting that there were a number of drains and other outflows along the Canal (Plate 12.2). These could potentially provide a zone of cleaner water where they enter, or help to oxygenate a small area due to the action of the cascading water entering the Canal. In both circumstances, these could create small, localised refuge areas of improved oxygenated water, although as stated, overall there are no suitable large scale fish refuges in this pound.

Plate 12.2. Outflow on the MSC, Trafford Park.

12.3 Barton Locks to Irlam Locks (approx. 3.2km) Immediately downstream of Barton locks on the northern bank is the mouth of Salteye brook (Plate 12.3). From analysis of the aerial image it appears that Salteye brook could offer reasonable refuge for fish. Photographs taken from the ground survey (Plate 12.4.) showed that the entrance to Salteye brook was easily passable,

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comprising of three culverts which allow fish to pass freely. Further investigation into Salteye brook through the GIS showed that the length of the stream was at least four kilometres in length, offering an ample refuge area.

Salteye brook

Salteye brook confluence

Plate 12.3. Aerial image showing the confluence of Salteye brook with the MSC immediately downstream of Barton locks (right of picture).

Plate 12.4. The mouth of Salteye brook. Downstream of Salteye brook there were no other sources of external ‘escape’ refuges from the MSC in this pound, emphasising the brook’s importance. Bents Lane brook, however, may provide an oxygenated zone at its inflow, but a small weir makes it impassable for coarse fish (Plate 12.5).

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Plate 12.5. Bents Lane brook Continuing downstream, the only other point of interest was the old course of the Irwell, immediately downstream of the Hulme ferry crossing. The aerial photography (Plate 12.6) showed the old course had the potential to provide a certain level of refuge from the MSC, although further analysis from the boat survey indicated that the entrance to this section becomes exposed and impassable during low flows.

Old course of the Irwell MSC

Plate 12.6. Aerial Image showing the entrance to the old course of the River Irwell near Irlam.

12.4 Irlam Locks to Latchford Locks (approx. 12km) The first notable point regarding this stretch is the entry of the River Mersey, downstream of the of the Irlam railway bridge. The weir (Plates 12.7 and 12.8) measured sixty metres in width, and approximately 2 metres high making it impassable to coarse fish, but passable to salmonids (which have been reported further up the Mersey catchment). Although impassable to coarse fish, the cascade effect of the water entering the Canal (especially in higher flows) would create a highly localised oxygenated region, which could act as a temporary refuge. For migratory

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salmonids, the Mersey would act as an extremely effective refuge and allow access to spawning habitats further up the Mersey catchments (the River Goyt).

MSC River Mersey

Plate 12.7. Aerial image of the Mersey weir entering the MSC

Plate 12.8. Weir at the entrance of the River Mersey into the MSC The next potential refuge is downstream of Cadishead at the confluence of Glazebrook (Plates 12.9 and 12.10). Analysis from aerial imagery and GIS indicated that Glazebrook would provide good refuge from the MSC. The mouth of the brook measured approximately ten metres wide, and was approximately twelve kilometres long providing adequate refuge area (although further analysis of barriers to movement will show how much of the brook is available for refuge).

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Glazebrook

Glazebrook confluence

Plate 12.9. Confluence of Glazebrook with the MSC

Plate 12.10. Mouth of Glazebrook Beyond Glazebrook, Redbrook enters the MSC roughly four hundred metres downstream on the opposite bank (southern bank). Although smaller than Glazebrook, Redbrook would also provide refuge from the MSC (Plates 12.11 and 12.12). Similarly, assuming there are no obstructions in channel to prevent fish movement, Redbrook appeared to be suitable to accommodate fish populations. The stream provides 11.5km of potential refuge (Redbrook splits into Caldwell Brook and Sinderland Brook approximately 3.5km from the MSC confluence).

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Redbrook confluence

Redbrook

Plate 12.11. Confluence of Redbrook with the MSC.

Plate 12.12. Mouth of Redbrook. Further downstream at Rixton junction (Plate 12.13), there are two potential refuge points. Firstly is the River Bollin, which like the Mersey has records of salmon migration. Again, aerial imagery of the confluence highlighted that the Bollin is a reasonably large river that would provide good refuge from the MSC. A previous walkover survey by APEM (2004) of the Bollin catchment, mapped fisheries habitats and obstructions to salmonid migration. This survey showed that at least three kilometres of river is available as a refuge, prior to the first major obstruction (Heatley weir) being encountered.

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River Mersey

MSC

River Bollin

Plate 12.13. MSC - Rixton junction showing the confluence with the River Bollin and where the River Mersey leaves the MSC. The River Mersey on the opposite bank could also offer important refuge. Three kilometres of good quality river habitat are available with a modest flow regime, offering considerable potential as a refuge for both migratory salmonids and coarse fish, although more detailed water quality investigation (particularly with regard to oxygen concentration) would be required. Woolston weir (three kilometres downstream from the MSC confluence) acts as a barrier to coarse fish, and although is a barrier to migration, a fish pass offers passage to migratory salmonids. A further 7km downstream, Howley weir represents the tidal limit of the River Mersey. Approximately five hundred metres beyond Rixton junction, on the southern bank, Sow Brook enters the MSC (Plate 12.14). Interrogation of the GIS showed that Sow Brook could offer up to 2.1km of potential refuge (depending on any obstructions to fish movement). Aerial photography showed that Sow Brook is a relatively small narrow stream, measuring three to four metres in width near its mouth. Ground survey photographs (Plate 12.15) confirm this, suggesting that Sow Brook could offer some refuge for fish but mainly restricted to higher flows, as the brook to be relatively shallow.

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Sow Brook confluence

Sow Brook

Plate 12.14. Confluence of Sow Brook and the MSC.

Plate 12.15. Mouth of Sow Brook. Beyond Sow Brook approximately 650m downstream, the next point of interest is provided by another deviation from the MSC, the old course of the River Irwell. Aerial photography (Plate 12.16) shows that the old course could provide refuge. However similar to the old course deviation in the Barton to Irlam pound, this point of potential refuge is blocked approximately two hundred metres from the MSC and therefore offers little refuge.

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MSC

Old course of the Irwell

Plate 12.16. Old course of the Irwell. From the point of the old course of the Irwell, there are two more potential points of refuge, before the end of the study zone at Latchford locks. Massey Brook and Thelwall Brook are located 2.2km and 3.2km downstream from the old course of the Irwell respectively. Aerial imagery showed that Massey Brook is again a small stream that could offer potential refuge for fish (Plate 12.17). The GIS showed that Massey Brook could offer up to 4km of potential refuge, but once again any obstructions to fish movement could limit how much refuge habitat is available.

Massey Brook confluence

Massey Brook

Plate 12.17. Confluence of Massey Brook with the MSC. Thelwall Brook provides the last potential point of refuge within the study zone. Located approximately 450m upstream of Latchford locks, aerial photography showed that the brook is very small at its confluence, providing very little refuge for larger fish further upstream the brook. The GIS showed that the brook could offer up to 2.5km of potential refuge habitat, however further investigative work would be required to determine the extent of habitat. Ground survey photographs (Plate 12.19) indicated that it would take significantly higher flows for the brook to become

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accessible. It is worth noting that in lower flows, although inaccessible, the mouth of the brook cascades into the MSC, providing some small localised aeration.

Thelwall Brook confluence with the MSC

Thelwall Brook

Plate 12.18. Confluence of Thelwall Brook with the MSC.

Plate 12.19. Thelwall Brook.

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13.0 RECOMMENDATIONS AND CURRENT KNOWLEDGE GAPS 13.1 Monitoring and scientific investigation

1. Using data currently available it has not been possible to provide a robust assessment of natural recruitment of fish within the system. This leaves many questions unanswered regarding the environmental parameters (both chemical and physical) that may be responsible for constraining recruitment. Without such data, the effective management of these fisheries will always be compromised and informed decisions cannot be made regarding the need for additional stocking or habitat manipulation. Recommendation 1 Initiate an annual sampling programme to assess the status of 0+ fishes using appropriate methodologies such as point sampling with reduced anode diameter and micromesh seine netting of littoral habitats (Copp 1989; Pinder, 2001). These methods offer excellent value in terms of the quality of data collected and the relatively low demands on man-power required to undertake such surveys. It is recommended that a minimum of two surveys are performed per year. By timing the first survey to target young larvae as soon as later spawning species have hatched will provide an initial assessment of spawning success and thus indicates that a species is not constrained by habitat bottlenecks. The later survey should then be carried out in September, when the presence and condition of species will provide a prediction of recruitment strength.

2. Although the availability of larger food items is currently plentiful and does not appear to be restricting adult performance, it is not possible at present to ascertain whether recruitment is being restricted or denied by a lack of appropriate food items to satisfy early stages of development. The lack of suitable food may be an indication of water quality issues. Recommendation 2 In order to elucidate whether primary productivity and food availability is limiting fish populations, a detailed examination of gut contents will be required from 0+ fish captured in fry surveys.

3. Although the availability of potential spawning and nursery habitats are known to be limited within certain areas of the catchment, few data currently exist regarding the abundance and distribution of such habitats. Furthermore, both temporal and spatial data are lacking regarding the occurrence of spawning (be it successful or unsuccessful).

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Recommendation 3 Previous APEM habitat surveys of the Rivers Bollin and Goyt have facilitated the quantification of habitat limited spawning potential. In order to elucidate how habitat constraints may be limiting the natural recruitment of fish populations, such surveys will need to be conducted on a catchment wide scale. By focussing such surveys around expected spawning seasons, physical examination for eggs, within such habitats will also allow spawning sites to be mapped. This would allow preliminary observations of egg viability to be made, while identifying specific sites for more detailed examination in the future.

4. The impact of intersexuality on spawning success and egg survival to hatching is currently poorly understanding. Recommendation 4 In order to assess the ecological impact of intersex on fish populations in the MSC and surrounding catchment, a simple and rapid comparison could be achieved by comparing the fertilisation rate of the eggs of perch and roach, from both within and outside Salford Quays. Further experimental comparisons could be made between the fertilisation and hatching success of healthy stock originating from aquaculture and the stocks within the Canal. Such data would allow the quantification of the impacts of intersex on spawning success within contaminated habitats.

5. The timing of salmon migration patterns has not yet been established on the Mersey. Recommendation 5 To understand how river discharge and water quality may influence the timing of adult salmon (and sea trout) ascending the MSC, the Woolston trap would need to be operated on a monthly basis. Such monitoring would also provide an estimate of the total number of salmon entering the lower MSC. While the future monitoring of parr populations would provide an indication of the age and annual timing of smoltification, it is suggested that a scoping study is initiated to assess the feasibility for the use of Passive Integrated Transponder (PIT) telemetry, to investigate the precise temporal pattern of downstream migrations of both parr and smolts.

6. The numbers of adult salmon successful in navigating the MSC and participating in spawning is not currently known. Without such data it will not be possible to assess the instream survival of eggs and parr, which are

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fundamental requirements for the future management of recovering salmon stocks in the Mersey Basin.

Recommendation 6 Mapping of redds in conjunction with data from the Woolston Trap would allow an estimate of the numbers of fish unable to reach suitable spawning grounds (i.e. potential mortality within the MSC). The mapping of redds could be rapidly achieved with the use of high definition aerial photography and would also facilitate studies into hatching success, growth and general health of juveniles to be monitored.

7. Are there species of coarse fish not presently in the Mersey system, which may outperform those species that have previously been stocked? Recommendation 7 Look into the possibility of stocking surface dwelling cyprinids such as bleak. If spawning can be achieved, this species is often prolific, forming huge shoals as seen on the Severn, Wye, Thames and Great Ouse. The benefits of the addition of this species are twofold. 1.) Bleak would provide an additional species to satisfy anglers in the MSC and would probably spread throughout the canal as they naturally occupy the surface water layers, where oxygen levels are usually more favourable; 2.) The presence of this fish in the Lower Irwell and upper MSC would provide a visual spectacle for the general public. This species constantly breaks the surface as they rise to take food which would provide a tangible sign of water quality improvements. 8.

Why have eels not returned to the upper catchment? Recommendation 8 The Mersey system appears to be unique, in that it is the only watercourse in the British Isles known not to support the species Anguilla anguilla. Current literature suggests that pheromones may play a role in acting as a signal for migratory conspecifics. This could easily be tested by translocation of elvers from the estuary or other rivers, to the Bollin, Mersey and Irwell. Future growth and health of the initial stocking could then be monitored, with the Woolston trap then used to monitor the return of elvers to the catchment. It is strongly recommended that a study for the feasibility for the reintroduction of eels and migratory lamprey should be initiated.

9. What degree of impact do instream barriers currently have on the recovery of fish populations?

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Recommendation 9 As many as 500 barriers to fish migration are thought to exist throughout the Mersey Basin. With the upper tributary rivers of the catchment (e.g. River Dean) identified as highly important areas for salmonid recruitment, it is essential to address both the distribution and impact of individual structures throughout the catchment. Rapid data collection from aerial surveys, in conjunction with habitat mapping would facilitate the best future management of such structures, allowing the provision of best financial and ecological value mitigation options.

13.2 Catchment Management Recommendations 1. Creation of ‘Off River Supplementation Units’ (ORSUs) Due to historical river engineering throughout the catchment, few habitats exist in which fish, particularly larvae and juveniles, are able to seek shelter from high flows. The strategic provision of such habitats would also benefit both phytophilic spawning and act as important nursery areas for all species. The creation of such habitats along the length of the MSC could provide shallow waterbodies, capable of maintaining oxygen levels from natural wind action on the water surface. The addition of macrophytes to such areas would provide important spawning and nursery areas, but, along the course of the MSC would also act as safe havens in times of poor water quality within the Canal. 2. Creation of marginal shelf habitats in the lower Irwell and upper MSC. The lower River Irwell and upper MSC currently lack any suitable habitat for the requirements of coarse fish throughout many of their life history stages. In addition to adult habitat being severely limited, there is a complete lack of spawning and nursery habitats. The creation of a marginal shelf (0.5m wide x 1m deep) would eventually provide a marginal zone of dense macrophytes. As well as directly enhancing recruitment, these areas would also provide a refuge from elevated flows and predation, thus increasing survival rates. 3. Jet washing of spawning gravels Jet wash gravels on the Goyt where salmon are known to have spawned. This would enhance the incubation and hatching success of the eggs thus providing more parr. The poor spawning of rheophilic species throughout the catchment would also improve the chances of natural recruitment, should gravels be cleaned of algal slime, sewage fungus and fine sediments.

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REFERENCES Alabaster, J.S., Shurben, D.G. and Mallet, M.J. (1979) The survival of smolts of salmon Salmo salar L. at low concentrations of dissolved oxygen. Journal of Fish Biology 15, 1-8. Alabaster, J.S. and Lloyd, R. (1982) Water quality criteria for freshwater fish. Butterworth Scientific. London. APEM (1989) Salford Quays Fisheries Investigations: Phase II. APEM Ltd., Manchester. APEM (1990) Mersey Basin water quality study, APEM Ltd., Manchester. APEM (1991) Salford Quays Fisheries Investigations: Phase III. APEM Ltd., Manchester. APEM (2004) River Bollin habitat survey for migratory fish. Project Report: EA 763. APEM (2006) River Goyt walkover habitat survey. Project Report: EA 877. APEM (2007) Manchester Ship Canal: water quality review. Project Report: 410039. Armstrong, J.D. and Griffiths, S.W. (2001). Density-dependent refuge use among over-wintering wild Atlantic salmon juveniles. Journal of Fish Biology 58(6), 15241530. Armstrong, J.D., Kemp, P.S., Kennedy, G.J.A., Ladle, M. and Milner, N.J. (2003) Habitat requirements of Atlantic salmon and brown trout in rivers and streams. Fisheries Research 62(2), 143-170. Baker, C.F. and Hicks, B.J. (2003) Attraction of migratory inanga (Galaxias maculates) and koaro (Galaxias brevipinnis) juveniles to adult galaxiid odours. New Zealand Journal of Marine and Freshwater Research 37, 291-299. Balon, E.K. (1975) Reproductive guilds of fishes: a proposal and definition. J. Fish. Res. Bd Can 31, 821-864. Balon, E.K. (1981) Additional and amendments to the classification of reproductive styles in fishes. Environmental Biology of Fishes 6, 377-389. Baras, E., Lambert, H. and Philippart, J.C. (1994) A Comprehensive Assessment of the Failure of Barbus-Barbus Spawning Migrations through a Fish Pass in the Canalized River Meuse (Belgium). Aquatic Living Resources 7(3), 181-189. Bellinger, E.G., Hendry, K and White, K.N. (1993) Nutrient cycling in an enclosed dock and its biological implications. In: Urban Waterside Regeneration: Problems and

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Prospects. (Ed: White, K.N., Bellinger, E.G., Saul, A.J., Symes, M and Hendry, K.) Ellis Horwood, Chichester. P 358-366. Beresford, N., Jobling, S., Williams, R. and Sumpter, J.P. (2004) Endocrine disruption in juvenile roach from English rivers: a preliminary study. Journal of Fish Biology 64, 580-586. Biktashev, V.N, Brindley, J. and Horwood, J.W. (2003) Phytoplankton blooms and fish recruitment rate. Journal of PlanktonResearch 25 (1), 21-33. Braum, E., Peters, N. and Stolz, M. (1996) The adhesive organ of larval pike Esox lucius, (Pisces). Internationale Revue der Gesamten Hydrobiologie 81, 101-108. Braun, N., Lima de Lima, R., Moraes, B., Lucio Loro, V and Baldisserotto, B. (2006) Survival, growth and biochemical parameters of silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), juveniles exposed to different dissolved oxygen levels." Aquaculture Research 37 (15), 1524-1531. Breitburg, D.L., Rose, K. A. and Cowan Jr, J.H. (1999) Linking water quality to larval survival: predation mortality of fish larvae in an oxygen-stratified water column. Marine Ecology-Progress Series 178, 39-54. Briand, C., Fatin, D. and Legault, A. (2004) Role of eel odour on the efficiency of an eel, Anguilla anguilla, ladder and trap. Environmental Biology of Fishes 65, 473-477. Burleson, M.L., Wilhelm, D.R and Smatresk, N.J. (2001). The influence of fish size on the avoidance of hypoxia and oxygen selection by largemouth bass. Journal of Fish Biology 59(5), 1336-1349. Clough, S. and Ladle, M. (1997) Diel migrations and site fidelity in a stream-dwelling cyprinid, Leuciscus leuciscus (L.). Journal of Fish Biology 50, 1117-1119. Cooke, G.D., Welch, E.B., Peterson, S.A. and Newroth, P.R. (1993) Restoration and Management of Lakes and Reservoirs, 2nd edn. Boca Raton, USA: CRC Press, 548 pp. Copp, G.H. (1989) Electrofishing for fish larvae and 0+ juveniles: equipment modifications for increased efficiency with short fishes. Aquaculture and Fisheries Management 20, 453-462. Corbett, J. (1907) The River Irwell: pleasant reminiscences of the nineteenth centuary and suggestions for improvement in the twentieth. Abel Heywood, London. Cunjak, R.A. (1996). Winter habitat of selected stream fishes and potential impacts from land-use activity. Canadian Journal of Fisheries and Aquatic Sciences 53, 267282. Dunn, J.F.R. and Hochachka, P.W. (1986) Metabolic responses of trout (Salmo Gairdneri) to acute environmental hypoxia. Journal of Experimental Biology 123, 229-242.

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Edwards R.W., Williams, P.F. and Williams, R. (1984). Ebbw. In: Ecology of European Rivers (Ed. Whitton, B.A.) Blackwell Scientific publications, Oxford. effluent. Environment Agency R&D Publication P7.

Environment Agency (1997) The quality of rivers and canals in England and Wales 1995. HMSO, London. Environment Agency (1998) The identification of oestrogenic substances in STW Environment Agency (2002a). The identification of oestrogenic effects in wild fish – Phase II. R&D Technical Report W2-014/TR. Environment Agency (2002b). Manchester Ship Canal Project Flore, L. and Keckeis, H. (1998) The effect of water current on foraging behaviour of the rheophilic cyprinid Chondrostoma nasus (L.) during ontogeny: Evidence of a trade-off between energetic gain and swimming costs. Regulated Rivers: Research and Management 14 (1), 141-154. Fraser, J.A.L and Clark, E.R. (1984) The effects of a settled industrial domestic sewage works effluent from percolating filters on the embryo viability and hatching success of rainbow trout Salmo gairdneri Richardson. Journal of Fish Biology 25, 393-403. Gimeno, S., Komen, H., Venderbosch, P.W.M. and Bowmer, T. (1997) Disruption of sexual differentiation in genetic male common carp (Cyprinus carpio) exposed to an alkylphenol during different life stages. Environmental Science and Technology 31, 2884-2890. Griffiths, S.W. and Armstrong, J.D. (2002). Rearing conditions influence refuge use among over-wintering Atlantic salmon juveniles. Journal of Fish Biology 60(2), 363369. Gross-Sorokin, M.Y., Roast, S.D and Brighty, G.C. (2006) Assessment of Feminization of Male Fish in English Rivers by the Environment Agency of England and Wales. Environmental Health Perspectives 114, s-1. Harper, E. (2000) The Manchester Ship Canal: water quality report. Report for Environment Agency, Manchester Ship Canal Company, North West Water and the Mersey Basin Campaign, Manchester. Harwood, A.J., Metcalfe, N.B, Griffiths, S.W. and Armstrong, J.D. (2002) Intra- and inter-specific competition for winter concealment habitat in juvenile salmonids. Canadian Journal of Fisheries and Aquatic Sciences 59(9), 1515-1523. Hellawell, J.M. (1989) Biological indicators of freshwater pollution and environmental management. Elsevier Applied Science, London.

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Hendry, K., Conlan, K., Bewsher, A. and Hawkins, S.J. (1988) Disused docks as a habitat for estuarine fish: a nation-wide appraisal. Journal of Fisheries Biology 33, 239-241. Hendry, K. (1991) The Ecology and Water Quality Management of Disused Dock Basins and Their Potential for Alternative Uses. PhD Thesis, University of Manchester Hendry, K., Webb, S.F., White, K.N. and Parsons, A.N. (1993) Water quality and urban regeneration – a case study of the Mersey Basin. In: Urban Waterside Regeneration: Problems and Prospects. (Ed: White, K.N., Bellinger, E.G., Saul, A.J., Symes, M and Hendry, K.) Ellis Horwood, Chichester. Hendry, K., Cragg-Hine, D., O’Grady, M., Sambrook, H. and Stephen, A. (2003) Management of habitat for rehabilitation and enhancement of salmonid stocks. Fisheries Research 62(2), 171-192. Hickley, P. and Dexter, K.F. (1979) A comparative index for quantifying growth in length of fish. Fisheries Management 10 (4), 147-151.

Holland, D.G. and Harding, J.P.C. (1984) Mersey. In: Ecology of European Rivers (Ed. Whitton, B), Blackwell, Oxford, pp1 113-144. Houde, E.D. (1994) Differences between marine and freshwater fish larvae: implications for recruitment. ICES journal of marine Science 51, 91-97. Huet, M. (1959) Profiles and biology of Western European streams as related to fish management. Transactions of the American Fisheries Society 88 (3), 155-163. Hynes, H.B.N. (1971) The biology of polluted waters. Liverpool University Press, Liverpool. Jamet, J.L. (1993) Biology of the adult roach (Rutilus rutilus, L., 1758; Pisces: Cyprinidae). Lake Aydat Revue des Sciences Naturelles d’Auvergne 57 (1-4) 1992-1993. 23-33.

Jenkins, H.J.K. (1988) Lord Orford’s Voyage round the Fens in 1774., Cambridgeshire Libraries Publication, pp. 64. Jobling, S., Nolan, M., Tyler, C.R., Brighty, G. and Sumpter, J.P. (1998) Widespread sexual disruption in wild fish. Environmental Science and Technology 32, 2498-2506. Jones, P.D. (2006) Water quality and fisheries in the Mersey estuary, England: a historical perspective. Marine Pollution Bulletin 53, 144-154. Keckeis, H., Bauer Nemeschkal, E. and Kamler, E. (1996) Effects of reduced oxygen level on the mortality and hatching rate of Chondrostoma nasus embryos. Journal of Fish Biology 49 (3), 430-440. Li, W., Sorensen, P.W. and Gallaher, D.D. (1995) The olfactory system of migratory adult sea lamprey (Petromyzon marinus) is specifically and acutely sensitive to unique 104 Final Report – September 2007

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bile acids released by conspecific larvae. Journal of General Physiology 105, 569587. Lucas, M.C. and Frear, P.A. (1997) Effects of a flow-gauging weir on the migratory behaviour of adult barbel, a riverine, cyprinid. Journal of Fish Biology 50(2), 382396. Maitland, P.S. & Campbell, R.N. (1992) Freshwater Fishes of the British Isles. Harper Collins, London. Malborough, D. (1970) The status of the burbot Lota lota (L.) (Gadidae) in Britain. Journal of Fish Biology 2, 217-222. Mann, R.H.K. (1996) Environmental requirements of European non-salmonid fish in rivers. Hydrobiologia 323, 223-235. Mann, R.H.K., Bass, J.A.B., Leach, D.V. and Pinder, A.C. (1996) Temporal and spatial variations in the diet of 0 group roach (Rutilus rutilus) larvae and juveniles in the River Great Ouse in Relation to prey availability. Regulated Rivers. 13, 287-294. Metcalfe, N. B., Fraser, N.H.C. and Burns, M.D. (1999) Food availability and the nocturnal vs. diurnal foraging trade-off in juvenile salmon. Journal of Animal Ecology 68(2), 371-381. Miles, S.G. (1968) Rheotaxis of elvers of the American eel in the laboratory from different streams in Nova Scotia. Journal of the Fisheries Research Board of Canada 25, 1591-1602. Miller, S.H. and Skertchly, S.B.J. (1878) The Fenland Past and Present., Longmans Green & Co., London. Mills, C.A. and Mann, R.H.K. (1985) Environmentally-induced fluctuations in yearclass strength and their implications for management. Journal of Fish Biology 27 (suppl A), 209-409. Miyakoshi, Y., Hayano, H., Omori, H., Nagata, M. and Irvine, J.R. (2002) Importance of instream cover for young masu salmon, Oncorhynchus masou, in autumn and winter. Fisheries Management and Ecology 9(4), 217-223. Muller, R. and Stadelmann, P. (2004) Fish habitat requirements as the basis for rehabilitation of eutrophic lakes by oxygenation. Fisheries Management and Ecology 11, 251-260. Nash, K.T., Hendry, K and Cragg-Hine, D. (1999) The use of brushwood bundles as fish spawning media. Fisheries Management and Ecology 6, 349-355. Nash, K.T., White, K. and Hendry, K. (2003) The effect of water quality on coarse fish productivity and movement in the lower River Irwell and upper Manchester Ship

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Canal: a watercourse recovering from historical pollution, APEM Scientific Project MSC 484. Pentelow, F.T.K. (1955) Pollution and fisheries. Verh. Int. Ver. Limnol., 12, 768-771. Pinder, A.C. 2001. Keys to larval and juvenile stages of freshwater coarse fishes from fresh waters in the British Isles. Scientific publication No. 60. Freshwater Biological Association, Ambleside 134 pp. Pinder, A.C. and Gozlan, R.E. (2004) Early ontogeny of sunbleak. Journal of Fish Biology 64, 762-775. Pinder, A.C. (2005) Fish Populations In: Environmental consequences for flood risk assessment. Scoping Study (Phase 1), by D. Ramsbottom et al., 47-50. Bristol: Environment Agency (Report EX5126 R&D Technical Report) Pinder, A.C., Gozlan, R.E., Beyer, K. and Bass, J.A.B. (2005) Ontogenetic induced shifts in the ecology of sunbleak Leucaspius delineatus during early development. Journal of Fish Biology 67 (Suppl B), 205-217. Pinder, A.C., Riley, W.D., Ibbotson, A T & Beaumont, W.R.C. (2007) Evidence for an autumn downstream migration and the subsequent estuarine residence of 0+ year juvenile Atlantic salmon Salmo salar L., in England. Journal of Fish Biology 71, 260264.. Reckendorfer, W., Keckeis, H., Winkler G, and Schiemer F. (1999) Zooplankton abundance in the River Danube, Austria: the significance of inshore retention. Freshwater Biology 41 (3), 583-591. Rimmer, D. M., Paim, U. and Saunders, R.L. (1983) Autumnal Habitat Shift of Juvenile Atlantic Salmon (Salmo-Salar) in a Small River. Canadian Journal of Fisheries and Aquatic Sciences 40(6), 671-680. Sollid, J., De Angelis, p., Gundersen, K. and Nilsson, G.E. (2003) Hypoxia induces adaptive and reversible gross morphological changes in crucian carp gills. Journal of Experimental Biology 206 (20), 3667-3673. Sorensen. P.W. (1986) Origins of the freshwater attractant(s) of migration elvers of the American eel Anguilla rostrata. Environmental Biology of Fishes 17(3), 177-185. Spoor, W. A. (1990). Distribution of Fingerling Brook Trout, Salvelinus-Fontinalis (Mitchill), in Dissolved-Oxygen Concentration Gradients. Journal of Fish Biology 36(3), 363-373. Stadelmann, P. (1984) Die Zustandsentwicklung des Baldeggersees (1900 bias 1980) und die Auswirkung von seeinternen Massnahmen. Wasser, Energie, Luft 76, 85-95.

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Sumpter, J.P. (2002) Endocrine disruption in the aquatic environment. In: The handbook of Environmental Chemistry, Vol. 3, Part M: Endocrine Disruptors, Part II (Metzler, M., ed.), pp. 271-289. Berlin, Heidelberg: Springer-Verlag. Tesch, F.-W. (1991) Anguillidae In: The Freshwater Fishes of Europe, Clupeidae and Angullidae (Hoestlandt, H. ed.), pp. 388-437. Aula-Verlag Wiesbaden. Tosi, L. and Sola, C. (1993) Role of geosmin a typical inland water odour, in guiding glass eel, Anguilla anguilla (L.) migration. Ethology 95, 177-185. Valdimarsson, S.K., Metcalfe, N.B., Thorpe, J.E. and Huntingford, F.A. (1997) Seasonal changes in sheltering: effect of light and temperature on diel activity in juvenile salmon. Animal Behaviour 54, 1405-1412. Whalen, K.G. and Parrish, D.L. (1999) Nocturnal habitat use of Atlantic salmon parr in winter. Canadian Journal of Fisheries and Aquatic Sciences 56(9), 1543-1550. Wheeler, A. (1979) The Tidal Thames: The History of a River and its Fishes., Routledge & Kegan Paul, London. Wilson, K.W., D’Arcy, B.J. and Taylor, S. (1988) The return of fish to the Mersey estuary. Journal of Fish Biology 33 (Supplement A), 235-238. Wilson, J., Hendry, K, & Rebbeck, J., (2000). Oxygenation project on the Manchester Ship Canal in the North West of England. In: WEFTEC 2000. Anaheim, Calif. USA. Proceedings of the Water and Environmental Federation 73rd Annual Conference & Exposition. Zhou, B.S., Wu, R.S.S., Randall, D.J., Lam, P.K.S., Ip, Y.K and Chew, S.F. (2000) Metabolic adjustments in the common carp during prolonged hypoxia. Journal of Fish Biology 57, 1160-1171.

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APPENDIX I – Water Quality Data Although data are available from many more sites throughout the catchment, the sites of focus in the current review were chosen as they were considered the best spatial representation of water quality throughout the catchment. The following graphs focus on biochemical oxygen demand (B.O.D), dissolved oxygen and total ammonia. Historical records for these parameters are variable in their completeness on both a temporal and spatial basis, but where long-term datasets illustrate clear temporal trends, an additional graph displaying annual means is also included. Where error bars appear on the graphs, these signify minimum and maximum values, thus highlighting the extreme parameters that may be overlooked if only considering monthly means or 95 percentile values. The guideline and imperative (also known as mandatory) levels set out on the graphs relate to the EU FFD requirements for cyprinid fish. Where ‘greater than’ values are recorded for ammonia, it is likely that these sporadic peaks relate to storm sewage discharges.

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Mar-05

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Feb-05

0

Figure A15 Irlam Mean Monthly D.O. (mg/l) 2005 - 2006 12

10 100% compliance required for EC FFD guideline level

D.O. (mg/l)

8

50% compliance required for EC FFD imperative level 50% compliance required for EC FFD guideline level

6

4

2

Figure A16

123 Final Report – September 2007

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0

Ja nFe 05 b0 M 5 ar -0 Ap 5 r-0 M 5 ay -0 Ju 5 n0 Au 5 gAu 05 gSe 05 p0 O 5 ct -0 N 5 ov D 05 ec -0 Ja 5 n0 Fe 6 b0 M 6 ar -0 Ap 6 r-0 M 6 ay -0 Ju 6 n06 Ju l-0 Au 6 gSe 06 p0 O 6 ct -0 N 6 ov D 06 ec -0 6

B.O.D. (mg/l) 19 76 19 77 19 78 19 79 19 80 19 81 19 82 19 83 19 84 19 85 19 86 19 87 19 88 19 89 19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06

B.O.D. (mg/l)

APEM Scientific Report - 410039

River Mersey at Flixton

Mersey at Flixton Average Annual B.O.D. (mg/l)

9

8

EC FFD

7

6

5

4

3

2

1

0

Figure A17a Mersey at Flixton Average Monthly B.O.D. (mg/l)

12

10

EC FFD

8

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2

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Figure A17b

Final Report – September 2007

124

APEM Scientific Report - 410039

Mersey at Flixton Mean Annual D.O. (mg/l) 10 9 8 100% compliance required for EC FFD guideline level

D.O. (mg/l)

7 6

50% compliance required for EC FFD imperative level

5 4

50% compliance required for EC FFD guideline level

3 2 1 2006

2004

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Figure A18a Mersey at Flixton Mean Monthly D.O. (mg/l) 14 12

D.O. (mg/l)

10 100% compliance required for EC FFD guideline level

8

50% compliance required for EC FFD imperative level

6 4

50% compliance required for EC FFD guideline level

2

Figure A18b

125 Final Report – September 2007

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APEM Scientific Report - 410039

Mersey at Flixton Mean Annual Ammonia (mg/l) 3

Ammonia (mg/l

2.5 EC FFD

2 1.5 1 0.5

2006

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0

Figure A19a

Mersey at Flixton Mean Monthly Ammonia (mg/l) 3.5

Ammonia (mg/l

3 2.5 2 EC FFD

1.5 1 0.5

Figure A19b

126 Final Report – September 2007

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APEM Scientific Report - 410039

River Bollin at Heatley River Bollin at Heatley Mean Annual B.O.D. (mg/l) 12

10 EC FFD

B.O.D. (mg/l

8

6

4

2

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0

Figure A20a River Bollin at Heatley Mean Monthly B.O.D. (mg/l) 7 6 EC FFD B.O.D. (mg/l

5 4 3 2 1

Figure A20b

127 Final Report – September 2007

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APEM Scientific Report - 410039

Bollin at Heatley Mean Annual D.O. (mg/l) 12 100% compliance required for EC FFD guideline level

10

D.O. (mg/l)

8

50% compliance required for imperative level

6

4 50% compliance required for EC FFD guideline level

2

2006

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0

Figure A21a

River Bollin at Heatley Mean Monthly D.O. (mg/l) 2005-2006 18 16

D.O. (mg/l)

14 12

50% compliance required for EC FFD guideline level

10 8

100% compliance required for EC FFD guideline level

6 4

50% compliance required for imperative level

2 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05 Oct-05 Nov-05 Dec-05 Jan-06 Feb-06 Mar-06 Apr-06 May-06 Jun-06 Aug-06 Sep-06 Nov-06 Dec-06

0

Figure A21b

128 Final Report – September 2007

APEM Scientific Report - 410039

Bollin at Heatley Mean Annual Ammonia (mg/l) 1.6 1.4

Ammonia (mg/l

1.2 EC FFD 1.0 0.8 0.6 0.4 0.2

2006

2004

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2000

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1990

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1976

0.0

Figure A22a

River Bollin at Heatley Mean Monthly Ammonia (mg/l) 1.2

1.0

Ammonia (mg/l

EC FFD 0.8

0.6

0.4

0.2

Figure A22b

129 Final Report – September 2007

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0.0

APEM Scientific Report - 410039

River Goyt R.Goyt Average Monthly B.O.D. (mg/l) 2005-2006 7 EC FFD 6

B.O.D. (mg/l)

5 4 3 2 1

De c06

Ap r- 0 6 M ay -0 6 Au g06 O ct -0 6

Ja n06

Ju l-0 5 Se p05 No v05

M

ay -0 5

ar -0 5 M

Ja n05

0

Figure A23

R.Goyt Mean Monthly D.O. (mg/l) 2005-2006 16 14

100% compliance required for EC FFD guideline level

D.O. (mg/l)

12 10 8

50% compliance required for imperative level

6 4 2

Figure A24

130 Final Report – September 2007

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0

50% compliance required for EC FFD guideline level

APEM Scientific Report - 410039

R.Goyt Mean Monthly Ammonia (mg/l) 2005-2006

Ammonia (mg/l

1.2

EC FFD

1.0 0.8 0.6 0.4 0.2

Figure A25

131 Final Report – September 2007

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0.0