Increasing urban and industrial development, particularly during the 19 th and 20 th centuries,

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1 The return of salmon to cleaner rivers: England & Wales Guy W. Mawle 1 & Nigel J. Milner 2 1 Environment Agency, Waterside Drive, Aztec West, Almondsbury, Bristol BS12 4UD 2 National Salmon & Trout Fisheries Centre, Environment Agency, 29 Newport Road, Cardiff CF24 0TP 1. INTRODUCTION Increasing urban and industrial development, particularly during the 19 th and 20 th centuries, led to the gross pollution of rivers and their estuaries. When combined with increasing obstruction to migration, abstraction, and over-exploitation, this degradation of water quality resulted in the loss of salmon from many rivers across England and Wales. This paper documents the loss and the subsequent return of salmon (Salmo salar L.) to these rivers following the reduction of pollution over the past forty years. 2. DECLINE AND LOSS Prior to the industrial revolution, most of the rivers of England and Wales supported salmon populations, excepting the low gradient rivers of East Anglia. Netboy (1968) describes the previous abundance and subsequent decline of salmon stocks and their associated fisheries, including those of the Trent, Yorkshire Ouse, Thames, Mersey and Medway. 1

2 The losses were gradual. The Thames, which flows through London, was probably the first major river to lose its stock: the last salmon for over a century was recorded in The Mersey also ceased to produce salmon in the middle of the 19th century (Harris 1980). Evidence to the 1860 Commission into Salmon Fisheries highlights pollution as a key factor in the decline, and some cases, the loss of some salmon stocks (Anon 1860). For example, many of the productive salmon rivers of South Wales, including the Taff, were affected by pollution from coal mining, metallurgical industries, and sewage from the expanding population (Mawle et al. 1985). In The salmon rivers of England & Wales, Augustus Grimble (1913) wrote: The Bristol Avon, the Mersey, the Calder, the Weaver, the Taff, Ogmore, Loughor, Neath and Ebbw are. absolutely ruined (by pollution) and the Ribble and other fine rivers are only too sure to follow suit unless the law steps in. In the North East, the salmon fishery on the River Tees became defunct in the 1930s, whilst those of the Tyne and Ouse finally ceased in the 1950s (Axford et al., in prep.). Champion (1991) describes 1959 as the nadir for the Tyne, a description which would probably apply generally to water quality in salmon rivers across England and Wales. A national survey of water quality in 1958, classified 28 per cent of non-tidal rivers, and 59 per cent of tidal rivers as being doubtful; poor; or grossly polluted (NRA 1991). 2

3 At this time salmon stocks had apparently been lost from about 30 per cent of the catchment area of England and Wales (Fig.1). On the east coast the main losses were the Tyne, Wear and Tees in the north; the large Ouse and Trent systems which share the Humber estuary; and the Thames and Medway. The biggest losses on the west coast were the rivers of the South Wales coalfield and the Mersey in the north. 3. REDUCTION OF POLLUTION Stronger legal measures to control and reduce pollution were implemented in the latter half of the twentieth century including the Rivers (Prevention of Pollution) Acts 1951 to 1961, and the Control of Pollution Act Compliance with this legislation has required massive investment, both public and private, in wastewater treatment. As well as improved treatment of effluents, there was a reduction in the need to treat effluents as some heavy industries declined. For example, UK steel production dropped by a third from the 1960s to the 1990s (Office for National Statistics 1997). More marked has been the decline in the coal production which has fallen by about 80 per cent over the past 40 years; coke production has fallen by 71 per cent (National Statistics 2000). The consumption of coal to produce coal gas fell from 23 thousand tonnes in 1960 to nothing by 1977, as natural gas became available. The coal industry, including the associated production of coke and coal gas, has polluted rivers with suspended solids, ammonia, phenols, thiosulphates, and thiocyanates (Edwards 1981). Water quality has improved markedly in many rivers (Environment Agency 1998). The proportion of non-tidal rivers classed as grossly polluted or bad fell from 6.4 per cent in

4 to 0.4 per cent in 2000 (Fig. 2). There have been two main periods of improvement. The first was during the 1960 and 1970s. The second followed privatisation of the water industry in 1989 since when there has been stronger regulation, by the National Rivers Authority and subsequently the Environment Agency, as well as increased investment by the water industry, equivalent to billions of pounds each year at 1999 prices (Figure 3). Under the industry s current Asset Management Plan, investment will continue at this level until 2005 at least with further benefits for water quality. Water quality in estuaries has shown similar improvements. A notable example is that of the River Tyne, which Grimble (1913) described as having been the first salmon river in England. Up to 1980 much of the estuary was still grossly polluted. Even in 1990 water quality was poor for about 30 per cent of its length. Since 1995 all of it has been classed as of good or fair quality. The improvement was due to industrial decline (particularly the closure of gas works and their associated coke ovens) coupled with major investment in sewerage systems led to greatly improved estuarine water quality. Similar improvements occurred in the nearby rivers Tees and Wear. The reduction in ammonia levels on the Wear is shown in Figure Return of the salmon Since the 1960s, recovery has been dramatic in many rivers around the country. The principal index of this has been catch returns declared by licensed salmon anglers to the Environment Agency and its predecessors (Russell et al. 1995; Environment 2000b). Within the last three years, salmon have been recorded either through such declared catches or by other means 4

5 (including Environment Agency fisheries surveys and accidental captures by anglers) from almost all the catchments from which they had been lost (Figure 5). The recovering stocks, mostly in the North East and South Wales, have contributed 20 per cent of the declared rod catch of salmon in England and Wales for the last three years (Table 1). These changes have been all the more impressive because they have occurred against a wide scale decline in salmon stocks in many areas of the North Atlantic over recent decades, attributed to reduced marine survival (Crozier and Potter, 2000). 4.1 East coast rivers In the North East, the Tyne, Tees, and Wear all now support significant rod fisheries (Fig. 6). The most impressive example of recovery is the Tyne which, with a catch of 2513 salmon in 2001 is now the most productive rod fishery in England and Wales. All these rivers have been stocked with juvenile salmon to aid recovery, particularly the Tyne where 160,000 or more young salmon have been stocked annually as mitigation for the impact of Kielder reservoir. Since 1978, salmon are known to have been breeding again in the River Ure, a tributary of the Yorkshire Ouse, following a stocking programme (Axford 1991). Despite this, few salmon have, as yet, been reported caught by licensed salmon anglers from the Ouse which feeds the Humber Estuary; seventeen over the past ten years. Nonetheless, stock abundance now seems to be increasing. In the winter of 2000/1 about 300 redds were observed in the Ure, where high densities of juveniles have also been recorded in the Environment Agency s routine electrofishing surveys (Axford et al.; in prep.). In March 2001, a salmon kelt was accidentally caught by a coarse angler from the river Don, which enters the Ouse just 5

6 upstream of the Humber Estuary. There have also been reports from the Don of salmon being seen jumping in the centre of Sheffield, and in the adjacent river Aire in 2001 (Axford et al., in prep.). Between 1967 and 1993, there were over a hundred authenticated reports of salmon in the Trent, the other major river entering the Humber, including 20 authenticated sightings or captures in 1982 (Axford et al., in prep.). A tributary, the Dove, was stocked in 1998 with 150,000 salmon fry of Tyne origin. Other stockings were made in 2000 and 2001 and a Trent Salmon Trust has been set up to fund work to restoring a salmon population. In 2001, several salmon were seen leaping at weirs on the Dove, the first authenticated sightings of salmon in this tributary since one was caught by an angler at Egginton in 1932; redds were also observed. There is a Thames Salmon Trust which has led the funding of work to restore a salmon population to that river. Stocking has helped stimulate runs of several hundred salmon a year in the early 1990s, mostly captured by trap (Fig. 7). Up to 34 salmon a year, in 1996, have been reported caught by anglers (Environment Agency 2002b). These fish are thought to have been wanderers from other rivers or derived from stocking. A chain of fish passes has just been completed on 37 weirs up the Thames and its tributary, the Kennet. For the first time in over 150 years adult salmon can now potentially reach somewhere to spawn in the Thames catchment. The recent poor returns may be related to poor estuarine water quality during the summer and perhaps to changes in stocking practice. On the adjacent river Medway, returns have so far been confined to the occasional fish captured or observed in the lower reaches. 6

7 4.2 West coast rivers Salmon are once again returning to all the rivers in South Wales, which are also supporting stocks of juvenile fish, as recorded in electrofishing surveys, though in several rivers the numbers are still small. Mawle et al. (1985) relate the initial return of salmon to the Taff to improvements in water quality. The declared rod catch on this river reached a peak of 114 salmon in 1988; many were tagged fish derived from stocking as smolts. The future expansion of the stock on this river depends on the provision of access to significant spawning grounds, as well as the successful passage of fish over an estuarine barrage, recently constructed, and through its impoundment (Mawle 1991). Salmon have been attempting to enter the adjacent river Ely since 1991 but were stopped by a weir at the head of tide. That weir has been removed but the river is now affected by the same barrage as the Taff. The extent to which the barrage obstructs migration is unclear as yet but significant numbers of adult salmon and sea trout are passing it. Further west, the rivers Ogmore, Neath, Afan and Tawe are now all supporting significant rod fisheries for salmon (Table 1, Fig. 8) and more particularly sea trout (Salmo trutta L.). The Tawe has also been impounded in its estuary. The Stour, a tributary of the Severn, was once grossly polluted by effluents from the industrial West Midlands, known as the Black Country and largely fishless. A fisheries survey in 2000 found salmon in the river for the first time in more than a century (Environment Agency 2002b). 7

8 Further north, salmon have also recently returned to the Mersey. More than one billion pounds has been spent on cleaning up the effluents to this river. Three salmon were trapped at Woolston weir on the Mersey in 2001, though as yet there is no evidence that they can reach potential spawning areas. 4.3 The future The process of recovery is still continuing but for recovery programmes to work well all the conditions for salmon survival and production have to be in place. These include safe passage through clean estuaries, access to silt-free spawning areas, good environmental quality and flow regimes in rearing areas and finally access back to the sea for smolts. If just one of these requirements is missing, even intermittently, then the life cycle is broken and recovery is stalled or at best very slow. The slow progress with the return of salmon to the Thames is indicative of the difficulties faced on some rivers. As yet the large catchments of the Ouse, Trent, Thames and Mersey are not able to support a salmon fishery of any consequence, though this may happen with time. Nonetheless, the return of salmon to these rivers highlights the major improvements in environmental quality that have been achieved. Regardless of the interests of fishermen, the presence of salmon would seem to be valued by the general public. A household survey in the Thames catchment indicated that residents would be willing to pay about 12 million a year to establish a breeding population of salmon in the river (Spurgeon et al. 2001). 5. The decline of stocks in rural rivers 8

9 Where it has occurred, recovery of stocks in rivers affected by urban and industrial pollution has been noticeable because the affected rivers started from a very degraded position and contrasts with the wide-scale decline of salmon in the North Atlantic (Potter and Crozier 2000). In England and Wales, analysis of trends in anglers declared rod catches has shown that they had significantly declined (p<0.05) in 42 per cent of rivers over the period 1974 to 1998 (Locke in prep.). Superimposed upon the overall decline in salmon is a complex mosaic of change in catch patterns across England and Wales resulting from the influence of local factors (Milner 2000). Included in the declining stock group are rivers designated as Special Areas of Conservation rivers, such as the Itchen, Hampshire Avon, Camel, Wye, Usk, Teifi, Tywi and Dee (Fig. 8). These are located in the most rural and notionally pristine habitats in the country. Decline in these rivers is partly due to factors affecting survival at sea, but there is concern over the cumulative influence of several freshwater environmental factors. These are clearly not related to direct influence of point industrial or domestic pollution, but represent a suite of issues derived from diffuse pollution and river flow changes. Issues include subtle impacts of diffuse pollution from acidification, pesticides and other organic chemicals and silt loading. Acidification has been a well-known environmental problem in Wales since the early 1980s (Stoner and Gee, 1985; Milner and Varallo 1989). The mechanisms have been well described and there has been some success in reversing low ph using lime dosing and other methods (Scarr et al. 2002). Although the deposition of SO 2 and NOx has decreased through emission controls (NEGTAP, 2001) acidification is still a serious issues in the headwaters of some 9

10 major catchments such as the Wye and other rivers draining the upland regions of Wales and North West England. Intensive agriculture is thought to have a major impact on the freshwater environment through a variety of processes (Environment Agency 2000). Intensive stock grazing and changes in stock management (e.g. over-wintering of cattle and pigs in open fields; increased maize production for forage) cause field and stream-bank erosion leading to siltation of river beds. Such changes directly affect salmon by preventing successful egg incubation, trapping alevins in gravel, and smothering fry habitat (Theurer et al. 1998; Acornley and Sear, 1999). In addition, siltation may be having an indirect effect on fish production by causing loss of invertebrate production and reducing food availability. Similar concerns have been expressed for salmon habitat in the river Bush, Northern Ireland (Potter & Crozier 2000). The use and disposal of pesticides in the process of agriculture and forestry is also regarded as a serious issue (Fairchild et al. 1999). A survey of Welsh streams in 1997 showed that 95 per cent of sites surveyed had pesticide residues present and 26% of farms were a high pollution risk (Fig. 10). By 1999, following intensive farm campaigns by the Environment Agency to propagate best practice, the proportion of farms at high risk had reduced to 3 per cent, but pesticides were still present in 67 per cent of sites. The concern is that high levels can be anticipated in any areas where intensive sheep farming occurs. Sheep headage has increased significantly in many rural areas. Between 1980 and 1993 the total number of sheep increased by almost 40 per cent to just under 44 million (Sansom 1999). Sublethal effects of pesticides on salmon reproductive function have been demonstrated at concentrations well below their nominal Maximum Acceptable Concentration; a standard based on direct toxicity tests, upon which environmental standards are set (e.g. Moore and Waring 1998). In addition 10

11 to direct effects on fish, pesticides can be expected to have effects on insects, for that is their intended function. Organophosphate pesticides have been recognised as being injurious to human health and have been partially replaced by synthetic pyrethroid pesticides. However synthetic pyrethroids are far more toxic to invertebrates than organophosphate pesticides and several serious pollution incidents have occurred in which aquatic invertebrates were killed over long lengths of rivers. Establishing cause and effect in complex aquatic ecosystems is difficult, but recent reports of declining invertebrate numbers and diversity (Hayes & Frake 2002) may be attributable to the cumulative effects of low level organic contaminants as well as other environmental changes. Changes to flow patterns are thought to have arisen through a combination of causes varying in importance between catchments. For example, rod catches from the Southern chalk rivers (Hampshire Avon, Itchen, Test, From and Piddle) show a common pattern of rapid decline following successive droughts in the period 1989 to 1992 exacerbated by substantial abstraction. In contrast, on rain-fed rivers, the more recent increase in winter precipitation linked to climate change (McKenzie Hedger et al. 2000) combined with compacted soils or enhanced drainage will enhance run-off, and can be expected to increase soil erosion, siltation and egg washout in. Overgrazing in upland areas has been highlighted as a cause of increased run-off in recent years (Sansom 1999). Research on the River Dee (Davidson, pers comm.) indicates that salmon growth pattern in freshwater may be changing, linked to a warmer climate, leading to production of younger smaller smolts. Marine survival may be altered as it has been observed to increase with smolt age (Salminen 1997). 11

12 6. Summary The overall picture of salmon stock change around England and Wales is therefore a complex one of a broad-scale change, reflecting marines factors, on which is superimposed variable performance in rivers around the country each experiencing different circumstances. There are now more catchments in England and Wales with salmon than at any time for the last 150 years. The recovering rivers represent a significant victory in the long-term campaign against gross pollution that has come about through a combination of massive investment and fortuitous decline of extractive and heavy industries, combined with effective regulation. However, salmon rivers, including those that lie in wholly rural areas, are subject to a complex cocktail of damaging environmental changes, mainly resulting from intensive land use. Thus one set of problems has been replaced by another, which requires new understanding to establish the underlying mechanisms and new approaches to policy and management to find solutions. Acknowledgements We thank all the various Environment Agency staff for the information provided on the status of individual rivers including Roger Inverarity, Miran Aprahamian, Roy Sedgwick, Gary Cyster, Darryl Clifton-Dey, Peter Gough, Steve Thomas, and Jim Gregory. We are particularly grateful to Rob Evans for his help in the preparation of the figures. 12

13 References Acornley R.M. and Sear D.A. (1999) Sediment transport and siltation of brown trout (Salmo trutta L.) spawning gravels in chalk streams. Hydrological processes 23, Anon. (1860) Commission into salmon fisheries in England and Wales. Report and minutes of evidence. Chairman W. Jardine. HMSO, London. Axford, S.N. (1991) Re-introduction of salmon to the Yorkshire Ouse. In Strategies for the rehabilitation of salmon rivers (ed. D. Mills), pp Proceedings of a conference held at the Linnean Society November Axford, S.N., Firth, C.J. & McHarg, K.M. (in prep.). The decline and recovery of migratory salmonid stocks and their fisheries in the rivers of North East England in relation to the water quality of the estuaries. Champion, A.S. (1991) Managing a recovering river The river Tyne. In Strategies for the rehabilitation of salmon rivers (ed. D. Mills), pp Proceedings of a conference held at the Linnean Society November Edwards, R.W. (1981) The impact of coal mining on river ecology. In Mining and water pollution. Proceedings of a symposium organised by the Inst. of Water Engineers and Scientists. Paper 3, pp1-8. Environment Agency (1998) The state of the environment of England and Wales: fresh waters. Stationery Office, London. Environment Agency (1999) Welsh Sheep dip monitoring programme, Environment Agency Wales report, March

14 Environment Agency (2000) Agriculture and the environment. An impact statement prepared by the Environment Agency. Environment Agency (2002a) Rivers and estuaries a decade of improvement. General quality assessment of rivers and classification of estuaries in England and Wales. Environment Agency (2002b) Salmon and freshwater fisheries statistics for England and Wales, National Salmon and Trout Fisheries Centre of the Environment Agency. Fairchild, W.L., Swansburg, E.O., Arsenault, J.T. and Brown, S.B. (1999) Does an association between pesticide use and subsequent declines in catch of Atlantic salmon (Salmo salar) represent a case of endocrine disruption. Environmental Health Perspectives, 107(5), Frake, A. and Hayes, P. (2001) Report on the Millenium chalk streams fly trends study. Environment Agency report. Grimble, A. (1913) The salmon rivers of England & Wales. Kegan Paul, Trench, Trubner & Co. Ltd. London. Harris, G.S. (1980) Ecological constraints on future salmon stocks in England and Wales. In: Atlantic Salmon: its future (Ed. A.E.J. Went) pp Fishing News Books, Farnham, Surrey. McKenzie Hedger, M., Gawith, M., Brown, I., Connell, R., and Downing, T.E. (2000) (Eds) Climate change: Assessing the impacts identifying responses. The first three years of the UK Climate Impacts Programme. UKCIP Technical Report, UKIP and DETR, Oxford. Mawle, G.W., Winstone, A.S. & Brooker, M.P. (1985) Salmon and sea trout in the Taff past, present and future. Nature in Wales, New Series, 4, parts 1&2: Mawle, G.W. (1991) Restoration of the river Taff, Wales. In Strategies for the rehabilitation of salmon rivers (ed. D. Mills), pp Proceedings of a conference held at the Linnean Society November

15 Milner, N.J., Varallo, P.V., Effects of acidification on fish and fisheries in Welsh rivers and lakes. In Acid Waters in Wales (Eds Stoner, J.H., Gee, A.S. and Edwards, R.W.), Junk, The Hague. Milner, N.J. (2000) Changes in Migratory Fish Populations. Volume 7, Paper No. 10, pp In: Coastal futures, Proceedings of Coastal Management for Sustainability Review and Future Trends 2000, (Ed. R. Earll), CMS. Moore, A and Waring, C.P. (1998) Mechanistic effects of a triazine pesticide on reproductive function in mature male Atlantic salmon (Salmo salar L.) parr. Pesticide Biochemistry and Physiology 62, NEGTAP (2001) Transboundary Air Pollution: Acidification, Eutrophication and ground level Ozone in the UK. Report prepared by National Expert Group on Transboundary Air Pollution, DEFRA contract EPG 1/3/153, 314pp. NRA (1991) The quality of rivers, canals and estuaries in England and Wales: report of the 1990 survey. National Rivers Authority Water Quality Series No. 4. National Statistics (2000) Digest of United Kingdom Energy Statistics Stationery Office, London. Netboy, A. (1968) The Atlantic Salmon: a vanishing species. Faber & Faber Ltd, London. Potter. E.C.E. and Crozier, W.W. (2000) A perspective on the ocean life of Atlantic salmon. pp19-36 in: The Ocean Life of the Salmon. (Ed. D. Mills) Fishing News Books, Blackwell Science, Oxford. Office for National Statistics (1997) Motor vehicle production and steel production and consumption. Table 4.3 (in) Economic trends, annual supplement 1997 edition. Stationery Office, London. 15

16 Russell, I.C., Ives, M.J., Potter, E.C.E., Buckley, A.A., and Duckett, L. (1995) Salmon and migratory trout statistics for England and Wales, Data Rep., MAFF Direct. Fish. Res., Lowestoft, (38): 252pp. Scarr, A., Edwards, P., and Bishop, M. (2002) Acid waters remediation and long term monitoring in Wales. Environment Agency R&D Technical Report P2-246/TR.* Spurgeon, J., Colarullo, G., Radford, A.F., and Tingley, D. (2001). Economic evaluation of inland fisheries. Environment Agency R&D Project W2-039/PR/2 (Module B).* Stoner, J.H. and Gee, A.S. (1985) Effects of forestry on water quality and fish in Welsh rivers and lakes. Journal of the Institute of Water Engineers and Scientists, 39, Salminen, M., Relationships between smolt size, post smolt growth and sea age at maturity in Atlantic salmon ranched in the Baltic Sea. J. Appl. Ichthyol., 13, Theurer, F.D., Harrod, T.R. and Theurer, M. (1998) Sedimentation and salmonids in England and Wales. Environment Agency R&D Technical Report P194 for R&D Project P2-103.* * available from Environment Agency R&D Dissemination Centre, c/owrc, Swindon, Wilts. 16

17 River Mean annual rod catch of salmon ( ) Tyne 2236 Tees 412 Wear 98 Ouse 7 Thames <1 Ebbw <1 Rhymney <1 Taff 43 Ely <1 Ogmore 75 Afan 8 Neath 60 Tawe 77 Loughor 13 Ystwyth 13 Rheidol 27 Table 1: The mean annual rod catch declared by licensed salmon anglers for from rivers in England & Wales in which salmon stocks had previously been lost or severely depleted. 17

18 Figure 1: Catchments in England and Wales from which salmon stocks were apparently lost in the 20 th century. 18

19 Proportion (%) Grossly Polluted / Bad Figure 2: The proportion (%) of non-tidal river length surveyed in England and Wales that was grossly polluted or bad from 1958 to 2000 (NRA 1991; Environment Agency 2002a). 19

20 Good and fair quality rivers (percentage of classified river length) River quality Water industry investment Year Investment ( billion at 1999 prices) Figure 3: Investment in the water industry in relation to the proportion of river length classed as good or fair in England and Wales from 1970 to1996. (updated from Environment Agency 1998) 20

21 4 3.5 Ammonia, 95%ile, mgl Figure 4: Ammonia concentrations (95%ile) in the River Wear at Lamb Bridge from 1973 to

22 Figure 5: Catchments in England and Wales from which salmon have been recorded in the last three years ( ), stocks having been lost in the 20 th century. Dark shading indicates catchments from which licensed salmon anglers have declared rod caught salmon. Hatching indicates that although no licensed rod catch has been declared, salmon have been recorded by other means. 22

23 Tyne catch Tyne Tees Wear Tees and Wear catch Figure 6: The recovery of the salmon rod fisheries in the North East of England as indicated by the annual declared rod catch of salmon for the rivers Tyne, Tees and Wear from 1960 to

24 No. of salmon Year Figure 7: The number of salmon recorded in the Thames each year from 1970 to

25 Annual rod catch Ogmore 80 Afan 70 Neath Figure 8: The recovery of the salmon rod fisheries in South Wales, as indicated by the annual declared rod catch of salmon for three rivers, the Ogmore, Afan and Neath, from 1970 to

26 Salmon rod catch Figure 9: The declared rod catch of salmon from 1974 to 2001 for eight rivers in England and Wales designated as Special Areas of Conservation for salmon (rivers Itchen, Hampshire Avon, Camel, Wye, Usk, Teifi, Tywi, and Dee). 26

27 %positive for sheepdip % High risk farms 100 Percentage Figure 10: In a survey of sheep farming areas in Wales, the proportions (%) of (i) farms classified as high risk; and (ii) stream sites where sheep dip pesticides were recorded (Environment Agency 1999). 27