The number of salmon killed by diseases at Scottish fish farms rose to more than 8.5 million last year.

New figures released by the Scottish Environment Protection Agency (Sepa) reveal losses from all salmon farms have reached nearly 10% of production.

The main problem has been the spread of amoebic gill disease, blamed by some on the warmer seas caused by climate pollution.

In 2012, 13,627 tonnes of dead fish had to be disposed of by 230 fish farms along the west coast and on the islands, compared with 9717 tonnes in 2011 and 7159 tonnes in 2010.

This has raised questions about how such large amounts of diseased waste are safely disposed of, and how the process is regulated. Sepa and local authorities both say it is not their responsibility.

Anglers and environmentalists pin the blame on production methods and are demanding a halt to any expansion plans.

"It is clear from these massive mortality figuresthere are major problems," said Hugh Campbell Adamson, the chairman of the Salmon and Trout Association in Scotland. "When a large number of fish are closely confined, the likelihood of endemic disease is greatly increased."

Fish farmer Grieg Seafood declined to comment.