Fish Farms Cause Salmon Declines
Research Shows Reduction of Wild Stocks in Rivers with Aquaculture
Research suggests that salmon aquaculture operations have a negative impact on the survival and return of wild salmon stock in rivers that host fish farms.
A study funded by the Lenfest Ocean Program shows that wild salmon population generally decline in rivers that also host fish farms. In rivers where young salmon are forced to pass by aquaculture operations, the total number of wild salmon that survive and return to spawn by more than fifty percent on average compared to rivers without fish farms.
In an announcement of the new report, Study Lead Author Jennifer Ford says, "This report is the first global assessment of the impacts of fish farms on wild salmon populations, and the results are startling. The findings from our analyses varied in different regions, but by combining them, we see that there is a negative impact on wild salmon that is highly significant."
Salmon Study Goals - This latest study concerning the interaction of wild and farmed salmon has been published at PLoS Biology, a peer-reviewed online journal produced by the Public Library of Science. Researchers could see that there has been a decline in wild salmon abundance in the North Atlantic and northeast Pacific coast south of Alaska. It happens that these areas also host salmon aquaculture operations and studies have shown the negative effects of fish farms on young salmonids.
Until this study, it has been difficult to correlate these findings with changes in wild salmon populations and survival. The researchers looked at the survival of salmonids in areas with salmon fish farms and adjacent areas without the farms in Scotland, Ireland, Atlantic Canada, and Pacific Canada.
Study Findings - Researchers Ford and Meyers looked at existing data on abundance of five salmon and trout species in five different regions where they could compare population of salmonids exposed to aquaculture to unexposed control sites. Through mathematical modeling, the overall impact of fish farms could be made globally. The paired comparisons of exposed fish showed survival and return rates reaching fifty percent reductions per generation compared to the unexposed control sites. Averages recorded across populations and regions were statistically significant.
The authors conclude that improvements must be made in aquaculture management practices to reduce negative effects on wild salmon stocks. One interesting note in the study is that it appears wild stocks have been impacted more and have had greater mortality on the Atlantic versus the Pacific. One hypothesis is that Atlantic salmon species may be more vulnerable the negative impacts of interbreeding with escaped fish and some species of trout spend more time in coastal areas increasing their exposure to farmed fish.
Following a study in British Columbia, Canada that linked sea lice from fish farms to loss of migrating Pink salmon, this latest study by Ford and Meyers only highlights the need for better management of aquaculture operations. The future of wild salmon stocks will depend on it.
