Sea change spawns shrinking salmon

THE Atlantic salmon, one of Scotland's most iconic wild species, is shrinking.

Both the length and bodyweight of the fish is decreasing, according to scientists, who blame global climate change for depriving salmon of food.

Some salmon experts fear that if the trend continues there could be long-term consequences for the survival of the species as smaller fish generally lay fewer eggs.

The phenomenon is being observed among grilse, young salmon which have been at sea for just one year before swimming back to their home rivers to spawn. Grilse should be around 6lbs in weight but some have been found to be 30% lighter than normal. The fish should also be around 60cm long. But in the Tweed the number under 55cm has quintupled over the past decade.

Seymour Monro, chairman of the Atlantic Salmon Trust, a conservation charity, said: "This is extremely worrying, and if this trend continues and gets worse we will be worried about long-term survivability."

One study was carried out by Chris Todd, the professor of marine ecology at St Andrews University, who found that between 1997 and 2005 the bodyweight of an average grilse caught in the Pentland Firth and in the North Esk in Angus had declined by 15%.

On the Tweed, average length has also gone down as well as weight. Dr Ronald Campbell, fisheries biologist for the Tweed Foundation, said:

"Whereas 10 years ago, 3% of fish were under 55cm, that figure is now 15%. Ten years ago, fish over 70cm made up 50% of the catch. Now that's down to 22%. It's a pretty clear trend."

Most scientists agree that the cause of the changes lies in the fish's Atlantic feeding grounds to the north of Norway and east of Greenland.

"The fish are going to the right place but the food is not there," said Todd.