Effects of aquaculture on wild fish populations: a synthesis of data

Abstract

The potential adverse environmental effects of aquaculture have been the subject of considerable attention in both the media and the scientific literature. We undertook a synthesis of the published scientific literature, primarily concerning Atlantic salmon (Salmo salar), to assess the current data available regarding these potential effects. No data are available to test for the direct effects of aquaculture organisms on the demographics of wild fish populations. However, seven studies show that escaped salmon in the wild have lower fitness, as measured by survival and reproductive success, than native salmon. Thirteen other studies, encompassing 91 different traits, provide strong evidence of phenotypic differences between farmed and wild salmon, presumably because of artificial selection in the aquaculture environment. An additional 10 studies have documented significant genetic differences between farmed salmon and the wild fish with which they will interact, or potentially interact. Given the paucity of data regarding actual population consequences of escaped farmed fish on wild populations, and the documented differences between the two types of fish, it seems prudent to treat farmed fish as exotic species with potentially negative consequences for wild populations, particularly when the latter are of conservation concern.Key words: aquaculture, Atlantic salmon, artificial selection, fitness, introgression.