- Repeated escapes of farmed salmon could drive endangered
populations of wild Atlantic salmon to extinction, say scientists in the
British Isles.
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- There has been concern over the past decade that domesticated
salmon are breeding with native salmon, changing the genetic make-up of
the fish and damaging their ability to survive in the natural environment.
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- Until now, there has been little direct scientific evidence
but, according to a report published in the journal Royal Society Proceedings
B, the fears of environmentalists may be justified.
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- In a 10-year study, researchers from Ireland, Northern
Island and Scotland, found that wild salmon were vulnerable to extinction
because of genetic and competitive pressures from farmed fish.
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- Experiments with wild and farmed salmon hybrids in fresh
and marine water showed that the offspring of fish that had interbred had
a much lower survival rate - some 70% of the fish died in the first few
weeks of life.
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- Overall, farmed salmon were much less successful at surviving
in the wild compared with native salmon and were unlikely to return to
rivers to spawn.
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- However, they grew quicker than wild salmon and the ones
that did survive displaced many of their wild cousins from the rivers.
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- Extinction Fears
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- The team, led by Dr Philip McGinnity of Ireland's national
agency, the Marine Institute, and Professor Andy Ferguson of Queen's University
Belfast, warn that accidental and deliberate introductions of farmed salmon
could lead to extinction of vulnerable wild populations of Atlantic salmon.
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- They write in Proceedings B: "Our experiments, uniquely
carried out over two generations, demonstrate conclusively that these intrusions
lower survival and recruitment in wild populations and that repeated escapes
produce a cumulative effect, which could lead to extinction of endangered
wild populations."
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- Dr Paulo Prodohl, a co-researcher on the study, said
wild salmon were the product of thousands of years of evolution, which
had "fine-tuned" their genes to survive in the natural environment.
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- The introduction of new genes from fish that had been
bred in captivity could wreak havoc on local gene pools, he said.
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- He told BBC News Online: "What we need is higher
regulation and monitoring of the farming industry."
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- Marine Escapes
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- It is estimated that some two million Atlantic salmon
escape each year from fish farms in the North Atlantic - equivalent to
half the total number of wild adult salmon in the sea.
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- But Dr John Webster, of Scottish Quality Salmon, which
represents the Scottish salmon farming industry, said farmers were doing
whatever they could to keep fish in their cages.
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- He said the farmed salmon industry was working closely
with the wild salmon industry to agree on strategies.
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- "Cooperation and collaboration is a much more effective
way of dealing with these sorts of issues than improving regulations,"
he said.
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- © BBC MMIII
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- http://news.bbc.co.uk/1/hi/sci/tech/3195062.stm
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