Salmon crisis is all man’s fault

Catastrophic collapse in wild fish stocks can be curbed, say experts

THE number of wild salmon that die returning to the rivers in which they spawned could be halved if all the threats that man controls were managed or removed, say scientists.

Experts have been trying to explain why, 20 years ago, one in four smolts leaving their rivers in the UK would return every year as adult salmon to spawn and further the development of the species. Today, as few as one in 20 will come back.

The catastrophic collapse in salmon stocks has long been attributed to climate change, with conservationists insisting little can be done unless global warming is reversed.

However, the Atlantic Salmon Trust, based in Edinburgh, said up to twice as many fish would survive the epic annual journey to and from the ocean if the perils they faced were reduced.

The public has been largely shielded from the effects of the collapse because of the rise of salmon farming.

Ken Whelan, the trust’s research director, said: “It’s like a relay race with hurdles and it depends how many of the hurdles we can take down.

“The number of post-smolts declines due to cumulative effects of natural mortality as well as any man-made influences, such as fishing mortality in the form of by-catch.” Young salmon are at risk from river pollution caused by

industry, forestry and agricultural run-off. If water levels are low or the rivers are blocked by weirs they face delays that leave them vulnerable to predators such as tenth of global production, Scotland offers a premium product, at about 10 per cent above the world price.

Scottish salmon is typically given better quality feed, and farming can be less intensive so fish develop more muscle.

cormorants and goosanders. If they swim past a salmon farm they risk a swarm of sea lice.

In the estuaries, they must run the gauntlet of seals, whose populations have increased 500 per cent since 1978.

At sea they must navigate thousands of miles amid changing stocks of bait fish and plankton, on which they feed, steering clear of mackerel and herring nets spread by trawlers.

Mr Whelan said: “The lesson we must learn is that man’s influence can and does have an impact on these struggling populations.

“Management actions have historically taken place in freshwater but the emphasis is now moving to the coastal zone and the open ocean.”