[permaculture] BBC NEWS | Science/Nature | Extinction threat to wild salmon
ed sarten
esarten at yahoo.com
Thu Dec 13 18:10:47 EST 2007
This is not the only thing going on with salmon.The pollock fishery bycatch of king salmon is at its highest mark this year in the Bering seaas much is dumped or otherwise wasted.Our local biologists here on the Yukon River say up to 80,000 kings did not return as expected.How can we let this keep happening? Ed Sarten Ruby,ak.
"Lawrence F. London, Jr." <lflj at intrex.net> wrote:
Last Updated: Thursday, 13 December 2007, 19:05 GMT
Extinction threat to wild salmon
By Helen Briggs
Science and nature reporter, BBC News
Image courtesy of Alexandra Morton
Animals like bears rely on pink salmon
Wild salmon on Canada's west coast are being driven to extinction by parasites from nearby fish farms, a study claims.
Wild pink salmon around the Broughton Archipelago are declining rapidly and will die out within 10 years if no action is
taken, say researchers.
They say the data, published in Science, raises serious concerns about the global expansion of aquaculture.
Sea lice from farms are known to infect wild salmon, but until now the impact on wild populations has been uncertain.
"The impact is so severe that the viability of the wild salmon populations is threatened," said lead researcher Martin
Krkosek from the University of Alberta in Edmonton, Canada.
Modelling studies
Dr Krkosek and colleagues compiled data on the numbers of pink salmon in rivers around the central coast of British
Columbia.
It means that the probability of extinction is 100% and the only question is how long it is going to take
Dr Martin Krkosek
They compared populations of salmon that had come into contact with salmon farms with those that had not been exposed,
from 1970 to the present day.
Using a mathematical model of population growth rates, they show that sea lice from industrial fish farms are reducing
the numbers of wild pink salmon - a Pacific salmon species - to the extent that the fish could be locally extinct in
eight years or less.
Dr Krkosek said the population growth rate was "severely depressed".
"It means that the probability of extinction is 100% and the only question is how long it is going to take," he told BBC
News.
Natural parasites
Scientists say commercial open-net salmon farms are a "haven" for sea lice - naturally occurring parasites that attach
to the skin and muscle of salmon.
Map
Mature fish can survive being infested by a few lice but tiny juvenile salmon are particularly vulnerable to attack.
They come into contact with sea lice when they swim past fish farms on their migratory routes from rivers to the sea.
"Salmon farming breaks a natural law," explained study co-author Alexandra Morton, director of the Salmon Coast Field
Station, located in the Broughton Archipelago.
"In the natural system, the youngest salmon are not exposed to sea lice because the adult salmon that carry the parasite
are offshore. But fish farms cause a deadly collision between the vulnerable young salmon and sea lice. They are not
equipped to survive this, and they don't."
Scientists say there are a number of solutions to the problem, including moving farms away from rivers used by wild
salmon or putting farmed salmon in pens that are completely sealed off from the surrounding environment.
"The most obvious thing to do is to move the farm out of the way of the wild fish," Dr Krkosek told BBC News.
"Don't put them on the migration route, and don't put them near the spawning rivers. Another option is to move to closed
containment technology where the net pen is replaced with a physical barrier that prevents the exchange of parasites -
that would solve the problem too."
National treasure
Dr Krkosek said the impact of fish farms on wild salmon has been "an emotionally, politically and economically charged
debate" in Canada.
Image courtesy of Alexandra Morton
Fish moves to farms
"Salmon are considered a natural treasure to Canadians, but salmon farming has a lot of economic opportunity - we really
need economic activity to supplement coastal economies where fisheries and other resource centres are not doing as
well," he explained.
"So there are economic benefits to having salmon farms, but the way that it is currently being done is very damaging to
the environment and there are better ways of doing it."
The report in Science has implications for other parts of the world where salmon is farmed, such as Norway and Scotland.
Other species of salmon are known to become infected with sea lice, but they vary in their ability to withstand this.
Sid Patten, chief executive of the Scottish Salmon Producers' Organisation, said the Canadian research bore "little
resemblance to the situation in Scotland".
He said fish farmers, wild fish interests and the Scottish government had been working together for many years around
the north-west coast and islands to develop local area management plans "for the benefit of both wild and farmed salmon".
"I am delighted to report that there are very positive results coming from this process such as increased numbers of
wild salmon returning to some rivers," he said.
"This summer, the Scottish government presented our work to the Canadians who were very interested in exploring a
similar model for Canada."
SEE ALSO
Farm sea lice plague wild salmon
29 Mar 05 | Science/Nature
Farmed salmon 'infect wild fish'
03 Oct 02 | Science/Nature
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