Salmon farming is slowly killing off wild salmon, according to a recent study by Canadian scientists.
The study by Jennifer Ford and Ransom Myers, published in PLoS Biology, compared marine survival of salmonids in areas with salmon farming to adjacent areas without farms in Scotland, Ireland, Atlantic Canada, and Pacific Canada to estimate changes in marine survival concurrent with the growth of salmon aquaculture.
Based on results of mathematical modelling, the authors estimated a significant increase in mortality of wild salmonids (50% or more on average per generation) in regions where salmon farming is present, with Atlantic salmon populations being depressed more severely than Pacific salmon populations.
Previous studies have demonstrated that escaped farm salmon breed with wild populations to the detriment of the wild stocks, and that farmed salmon are a potent source of diseases and parasites for wild salmon.
The authors conclude, etter management should decrease the impact of salmon farming on a per tonne basis, although such improvements may not be able to keep pace with the growth of the salmon farming industry. The estimated reduction in survival of wild salmonids is large, and would be expected to increase if aquaculture production increases.
For more information, see the paper: Ford, JS and RA Myers (2008) A global assessment of salmon aquaculture impacts on wild salmonids . PLoS Biology 6, e33. doi:10.1371/journal.pbio.0060033