Project to probe salmon stock mystery

Donal Hickey says deaths are baffling scientists

SEVERAL countries are combining their research in a bid to come up with definitive reasons for the decline of Atlantic salmon. So complex is the issue it needs an international effort, according to Dr Ken Whelan, of the North Atlantic Salmon Conservation Organisation’s (NASCO) research board.

They are studying the poor survival rate of salmon at sea — deaths in some monitored stocks are now twice as high as in the 1970s — and want to gain a clearer understanding of what is happening the salmon before it begins it migration towards fresh water.

An international scientific project to investigate mortality has already started from Killybegs, Co Donegal, on board the Marine Institute research vessel RV Celtic Explorer.

Called the Salsea-Merge project, it is probing the migration and distribution of salmon in the northeast Atlantic. There will be three marine surveys during 2008 and 2009, conducted by Irish, Faroese and Norwegian research vessels and using DNA technology instead of conventional salmon tags.

Ireland has been involved in planning a programme that will follow juvenile salmon from southern Europe to the Barents Sea, using genetic technology. This method can identify individual fish caught at sea by analysing their genetic code, which can be matched back to their region, or river of origin.

In addition to the €5.5 million Salsea-Merge, a parallel programme took place last month with Canadian and US involvement, and the two surveys will collate their findings at a later date. Dr Whelan said an increasing proportion of salmon are dying at sea, and in some southern rivers of the north Atlantic salmon face extinction and no one understands why.

“There are many theories, but no sound research base on which rational action can be taken. That is what Salsea-Merge is all about, to provide answers,” he said.

Experts say the causes of the decline in Atlantic salmon stocks are many and complex, particularly in relation to the marine environment. Last week we had salmon fishermen in the west of Ireland, for example, calling for a seal cull amid claims seals are among the main salmon predators.

Pollution of river systems is another frequently-cited reason, as is overfishing. More recently, global warming and resultant changes in the marine environment are being mentioned.

For many years salmon farming has been blamed by some people for a decline in wild salmon stocks — a theory that is strongly denied by the aquaculture industry.

A report by the Worldwide Fund for Nature (WWF) and the Atlantic Salmon Federation says not enough is being done to prevent salmon farms from causing environmental damage.

Salmon farming in the sea lochs of Scotland has expanded to become a major industry. The report says the decline in stocks is linked to sea lice from farmed salmon sites and interbreeding between escaped fish and the wild population.

As the number of farmed salmon has exploded the population of its wild relatives has plummeted. Estimates suggest there are 48 caged salmon to every wild one in the North Atlantic.

The WWF report claims the Scottish authorities, and those in other countries, have failed to live up to international commitments to protect wild salmon. It says measures, such as locating farms away from the mouths of rivers, where migrating fish are most likely to be harmed, have not been implemented.

Recent improvements in fish husbandry, including the development and widespread use of vaccines, have also reduced the risk of disease transfer.

Evidence indicates salmon farming, as practiced in British Columbia, poses a low risk to wild salmon stocks, particularly when compared to other potential factors.

Limerick Institute of Technology (LIT) and other groups have started studies into depleting native salmon stocks and the salmon crisis on the River Shannon, as part of the Shannon Regional Rehabilitation Project set out by Shannon Regional Fisheries Board.

The project aims to develop a viable management system through research, ultimately leading to a healthy return of wild salmon numbers in the upper and middle Shannon.

Key partners within the initiative are the ESB, the Marine Institute, the Central Fisheries Board, University College Cork and LIT.

It will involve the attachment of radio technology to adult salmon and their movements being tracked to their spawning beds and movement patterns close to and through the Ardnacrusha and Parteen dams.

Other weirs will also be monitored to determine if fish have difficultly navigating and reaching their preferred spawning locations and this data will be contrasted with the free movement of fish entering the open tributaries below the dams.