TEMPERATURE changes in the North Atlantic could be the cause of the disastrous drop in salmon and trout stocks in Scotland, a Government Minister warned yesterday.

Scottish Office Minister Lord Sewel was commenting on reports that salmon could be wiped out on many of the great fishing rivers within two years.

The decline is very marked in north-west Scotland, and some experts point the finger of blame at disease spread by commercial fish farms.

But Lord Sewel said: ''We have certainly had two very bad years and it's difficult to understand why.

''It's not geographically specific; the east coast is suffering as badly as the west coast, so it can't be linked to fish farms because on the east coast we don't have any and yet the Aberdeenshire Dee is in a very bad state,'' he said on Radio 4.

''I suspect it is most likely to do with temperature changes in the North Atlantic, which affects the feed stock for the salmon itself.''

Habitat management and catch-and-release schemes could provide a way to deal with the problem, which would affect the Highland tourist industry, he said.

Dr James Butler, a fisheries biologist of the Wester Ross fisheries trust charity, told the programme the decline could partly be blamed on the El Nino effect.

''What the Minister said about temperature changes affecting salmon numbers is very true for all of the North Atlantic salmon-producing countries,'' he said.

''But he was ignoring the problem in north-west Scotland, which is the horrendous decline in sea trout. They have been decimated by something more complicated.''

The area was affected by a ''nasty cocktail'' of problems, of which climate change was one, Dr Butler said.

He urged the Scottish Office to act over the crisis, saying there had been a dramatic increase in predators, including grey seals, as well as over-fishing in The Minch, which affected the salmon and sea trout's food supplies.