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Sea Trout Decline

Sea trout, to many of us, rank as the most valuable of all our game fish here in the British Isles, providing unique night time sport on rivers from Cornwall to Caithness, from Connemara to Cumbria. The continued decline of sea trout stocks throughout the British Isles is a cause for great concern, both ecologically and economically.

Sea trout would appear to have been in general decline in many rivers for the past thirty years or so. In the absence of extensive scientific data, it is, of course, impossible for an individual angler to see the whole picture. We can only rely on what is often very limited personal experience, perhaps of a few local rivers; on occasional snippets of scientific information reported in the media; on river reports published over half a century in Trout and Salmon magazine; and on official catch statistics published by government agencies such as the Environment Agency in England and Wales and various agencies of the Scottish Executive such as the Fisheries Research Services and a number of District Salmon Fishery Boards. Nor has what appears to me to be a general decline been uniform throughout the country. Indeed, some rivers have reported recent improvements in sea trout catches, in particular those in the North East of England, though I suspect that this increase is, in large part, directly linked to the buy out of the Northumbrian drift nets. The most dramatic, and catastrophic, decline in sea trout stocks has occurred on the west coasts of Scotland and Ireland, coinciding with the growth of salmon farms from the early nineteen eighties. At one time, some of the best of our Scottish sea trout fishing was to be found on the great sea trout lochs of the north west highlands, on Loch Maree, Stack, More and Hope and on the great loughs and rivers of western Ireland. Each year, on every summer tide, large shoals of sea trout would run the short rivers to reach the lochs, where they would spend the summer months before making their way up the spawning streams in the autumn. When in the lochs, the sea trout could be caught during the day. Good catches of sea trout could be taken on a team of wet flies, fished, loch style, in front of a drifting boat, held steadily on age old drifts by skilled boatmen, while an irresistible dapped fly, fished on a good wind, might bring the better sea trout up from the deeper water. Sadly, the fishing on the great sea trout lochs is not what it once was. Stocks of sea trout have declined markedly in recent decades. Today, few fishermen make the annual pilgrimage to the west highlands in search of sea trout. Catches on the once famous sea trout rivers are a mere fraction of what they were. Boats on the lochs lie idle, hotels rooms empty.

A scientific study on the sea lice problem associated with the salmon farms ["Patterns of Sea Lice Infestations on Scottish West Coast Sea Trout: Survey Results 1997 - 2000" published by The Association of West Coast Fisheries Trusts] reported:

"In areas with epizootics (outbreaks of disease affecting many fish at one time), lice can directly cause the mortality of 30% to 50 % of all migrating sea trout smolts and 48% to 86% of all wild salmon smolts......

Studies in Norway, Ireland and Scotland estimate that, in salmon farming areas, most sea lice larvae are produced from farmed salmon, due to the far greater numbers of farmed hosts relative to wild hosts. This is reflected in significantly higher lice infestations on wild sea trout in salmon farming zones compared to farm free areas in Ireland and Norway. Similarly, in Scotland the highest burdens found on sea trout occurred in the salmon farming zone of the west coast. Consequently, in Norway, western Ireland and western Scotland, lice infestations are regarded as a major factor in the decline of wild salmon and sea trout populations....."

It is to be hoped that stricter controls combined with improved production techniques and a growing environmental awareness on the part of salmon farmers, fishery owners and politicians might one day halt, and perhaps even reverse, this sad decline and that one day the sea trout and the fishermen might return to the west highlands. One solution might lie in the development of systems of closed containment.

It has to be said, however, that there appears to have been a general, if less severe, decline in sea trout stocks also in areas where no salmon farms exist, for example in the rivers flowing into the Solway Firth and Moray Firth. So what other threats do the sea trout face? I would list the following as possible suspects:

1. Infestation by sea lice originating on the salmon farms of the Scottish and Irish west coasts. There can be little doubt as to the extent and nature of the problem, illustrated above. Despite the unforgivable refusal of the Scottish Government to accept the facts, it is clear to many of us that the salmon farms have been a major factor in the decline of sea trout stocks on many west coast rivers and lochs.

2. The uncontrolled growth in the populations of both grey seals and common seals around our coastline.

3. The overfishing of sandeels and other marine prey species.

4. Changes in sea temperatures.

5. Netting of sea trout at sea.

6. Diseases such as UDN.

7. Predation by anglers and poachers.

8. Afforestation of the upper catchments and the associated problems of both increased acidification and increased run-off of rainwater.

9. Increases in the numbers of protected species of predatory birds, in particular Goosanders.

10. Increases in the numbers of mink.

11. Agricultural insecticides and pesticides which find there way into rivers affecting both fish and invertebrate life.

12. Chemicals used in the control of the Foot and Mouth outbreak in 2001.

13. The use of hazardous sheep dipping chemicals, such as Cypermethrin.

14. The introduction of non indigenous fish species into sea trout rivers, in particular the stocking of farmed brown trout.

15. The increase in runs of salmon in sea trout rivers, putting pressure on limited spawning and nursery resources available to sea trout.

16. Climatic changes resulting in possible changes in the flow regimes of rivers, e.g. extended drought in summer, milder winters and big winter floods.

With all this, one wonders how the sea trout has survived at all. Given the political will, however, many of the above problems could be addressed, affording a degree of protection to the very fragile stocks of this most valuable game fish.

For more information on the environmental implications of the salmon farming industry, see The Salmon Farm Monitor .


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