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By tracking the long sea journey of a salmon
from, say, a remote mountain stream in west Cork to distant
Arctic seas, scientists can learn much about climate change.
Wild salmon, in their ocean migrations, are
among the world’s most natural and sensitive indicators of
climate change - says marine expert, Dr Ken Whelan - but the
decline in the number of salmon returning from the Atlantic
ocean to their home rivers in Ireland and Britain baffles
researchers.
Last year, €10m was spent on 47 ongoing research
projects - many under the auspices of the North Atlantic Salmon
Conservation Organisation (NASCO)
- and, hopefully, answers to the question of salmon survival
will be found. The research should also tell us more about
the effects of climate change in the seas and rivers.
Dr Whelan, director of the Marine Institute’s
Aquaculture and Catchment Management Services Team, says research
shows that water systems are changing fast. Water is getting
warmer, storms are getting stronger and food resources in
- and from - the ocean are under threat.
"Similar patterns are apparent in freshwater.
We have recently witnessed a series of unprecedented rainfall
deluges, which have caused massive landslides and the dislocation
of tonnes of mud, silt and peat," he told the Royal Irish
Academy.
Such weather disturbances lead to other changes,
including the appearance of new species off the coast and
the spread of non-native species around the coast and in freshwater.
The research carried out by Dr Whelan, and his colleagues,
shows that the Atlantic salmon is ideal for tracking climate
change.
Equally at home in fresh and saltwater, the
salmon traverses large areas of the planet in a relatively
short space of time and is endowed with an uncanny ability
to find its way home. Throughout its journey, the salmon collects
and stores a wide range of physical and scientific information.
Some oceans are warming, others are cooling
and melting ice is diluting the upper layers of the northern
and southern oceans. First to encounter these changes are
the long-distance migrants - such as shark, tuna and salmon.
Wild salmon numbers declined dramatically in
the late 20th century. Over the last 30 years, much money
and effort have gone into researching the life cycle of the
salmon, its interaction with its environment and the threats
it faces. We now have a clearer understanding of the salmon’s
life in rivers and inshore waters.
The hope is that this knowledge will result
in a cleaner environment, fewer obstructions, improved habitat
and reduced threats from commercial exploitation. Salmon numbers
continue to decrease, with fewer salmon returning from the
ocean. An increasing proportion are dying at sea. In some
southern rivers, on both sides of the north Atlantic, wild
salmon face extinction. No one fully understands why, but
pollution and the effects of fish farming are often cited
as reasons.
Theories abound, and more sound research is
needed. Recent advances in DNA analysis are significant, as
they make it possible to identify from a single fish scale
the river population to which a salmon belongs - a natural,
genetic identity tag.
Scientists are compiling a genetic river atlas
for the north Atlantic salmon population and a carefully-targeted
series of ocean surveys is underway.
SALSEA,
the international Salmon at Sea research programme, is designed
to use new technologies and it completed a series of voyages
during 2008-2009 to map salmon distribution and movement throughout
the north Atlantic.
Meanwhile, anglers on one of Scotland’s leading
salmon rivers will have to release every one of the fish they
catch until June, because of concerns over dwindling stocks.
Last month, the Tay District Salmon Fisheries Board announced
plans to introduce radical conservation, following a disappointing
season last year, which saw catches decline by as much as
50% on some stretches of the river.
Until now, anglers have been asked to follow
a voluntary code to release the first salmon they catch each
day and to only retain one fish in two. However, this year,
for the first time, those fishing the Tay are being urged
to return every salmon they catch up until the end of May.
From then until the end of the season, all female
salmon should still be released and a maximum of only one
male fish, weighing less than 10lb, retained each day. The
code will bring the Tay into line with the catch-and-release
policy first introduced on the Dee, Britain’s premier spring-salmon
river, 15 years ago.
Since 1995, the Dee Salmon Fishing Improvement
Association’s catch-and release-policy has allowed more than
30,000 salmon and grilse to be released back to the river,
to carry on upstream to their spawning grounds.
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