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
.
Sea Trout Articles |
|
