Introduction of non-indigenous organisms. In some cases, aquaculture affects stocks of wild and farmed fish through biological pollution. Atlantic salmonfithe dominant salmon species farmed frequently escape from net pens. As much as 40% of Atlantic salmon caught by fishermen in areas of the North Atlantic Ocean are of farmed origin. In the north Pacific Ocean, over
255,000 Atlantic salmon have reportedly escaped since the early 1980s and are caught by fishing vessels fromWashington to Alaska. Increasing evidence suggests that farm escapees may hybridize with and alter the genetic makeup of wild populations of Atlantic salmon which are genetically adapted to their natal spawning grounds. Such genetic alterations could exacerbate the decline in many locally
endangered populations of wild Atlantic salmon