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Dramatic Declines In Wild Salmon Populations Linked To Exposure To Farmed Salmon

Date:
February 13, 2008
Source:
PLoS Biology
Summary:
Comparing the survival of wild salmonid populations in areas near salmon farms with unexposed populations reveals a large reduction in survival in the populations reared near salmon farms. This study shows evidence on a global scale illustrating systematic declines in wild salmon populations that come into contact with farmed salmon.
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A global survey of wild salmon and trout populations reveals substantially reduced survival among those populations that migrate past salmon farms as juveniles on their way to the ocean.
Credit: United States Fish and Wildlife Service

Comparing the survival of wild salmonid populations in areas near salmon farms with unexposed populations reveals a large reduction in survival in the populations reared near salmon farms. Since the late 1970s, salmon aquaculture has grown into a global industry, producing over 1 million tons of salmon per year. However, this solution to globally declining fish stocks has come under increasing fire. In a new study Jennifer Ford and Ransom Myers provide the first evidence on a global scale illustrating systematic declines in wild salmon populations that come into contact with farmed salmon.

Previous studies have clearly shown that escaped farm salmon breed with wild populations to the detriment of the wild stocks, and that diseases and parasites are passed from farm to wild salmon. However, until now, there has been no assessment of the importance of these impacts at the population level and across the globe. Here, Ford & Myers compared the survival of salmon and trout that swim past salmon farms to the survival of those fish that never pass a salmon farm.

In five regions around the world, Ford and Myers find a significant decline in the survival of wild salmon populations that are exposed to salmon farms. This decline took place as farmed salmon production increased in each region. Combining these regional estimates, the authors find that wild populations suffer a reduction in survival or abundance of more than 50% when associated with farmed salmon.

These new results suggest that salmon farming could seriously compromise the persistence of the world's salmonid populations.

Citation: Ford JS, Myers RA (2008) A global assessment of salmon aquaculture impacts on wild salmonids. PLoS Biol 6(2): e33. doi:10.1371/journal.pbio.0060033


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PLoS Biology. "Dramatic Declines In Wild Salmon Populations Linked To Exposure To Farmed Salmon." ScienceDaily. ScienceDaily, 13 February 2008. <www.sciencedaily.com/releases/2008/02/080212085841.htm>.
PLoS Biology. (2008, February 13). Dramatic Declines In Wild Salmon Populations Linked To Exposure To Farmed Salmon. ScienceDaily. Retrieved July 28, 2015 from www.sciencedaily.com/releases/2008/02/080212085841.htm
PLoS Biology. "Dramatic Declines In Wild Salmon Populations Linked To Exposure To Farmed Salmon." ScienceDaily. www.sciencedaily.com/releases/2008/02/080212085841.htm (accessed July 28, 2015).

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