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Salmon stocks are inexplicably soaring in British streams and rivers after a serious decline that environmentalists blamed on sea lice from salmon farms. However experts warn that the surge may only be temporary.
"We still don't know why this is happening. It may just be a one-off or it could be a general trend to a return to healthy salmon numbers in our rivers," said Dr Anton Ibbotson, head of the English-based Game and Wildlife Conservation Trust’s salmon and trout centre.
"We used to get more than 2,000 salmon coming back to the river [Frome] every year," said Ibbotson. "Then, in the early 1990s, that figure plunged to under 500 and it has never recovered – until this year."
Scientists discovered the latest trend in statistics for salmon tagged and counted last year and from observations from river banks this year. Some of the most detailed figures available come from the river Frome in Dorset.
The Environment Agency said record numbers of salmon were counted in the River Tyne: 1,866 salmon between February and May compared to 581 in the same period of 2010. The agency has been counting migratory fish since 1996, BBC reports.
Scientists speculate that environmental changes at any stage in the salmon’s life cycles - shifts in ocean temperatures and currents, the availability of food in the open seas and overfishing - could have impacted the numbers of fish returning to their native rivers from the sea.
Numbers have also shot up in the past year in most of the east and north of Scotland plus the Tyne and Wear rivers.
"In addition, they seem to be coming back in a strong, healthy state," said Andrew Flitcroft, editor of Trout and Salmon magazine.
The Rivers and Fisheries Trusts of Scotland (RAFTS) has pointed out that salmon numbers have reversed except in the west of Scotland, where the majority of salmon farms are. The Trust blames sea lice infestations from the farmed salmon cages, which infect migrating wild salmon.
Wild salmon in this region have continued to drop while they have climbed on the east coast, which is free from salmon farms, the trust stressed.
"There is a clear need to direct research and funding into initiatives that will give greater protection to our wild salmon and sea trout," said Dr Alan Wells, policy and planning director of the Association of Salmon Fishery Boards (ASFB).
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