A study appearing in the December 14 issue of the journal Science shows, for the first time, that parasitic sea lice infestations caused by salmon farms are driving nearby populations of wild salmon toward extinction. The results show that the affected pink salmon populations have been rapidly declining for four years. The scientists expect a 99% collapse in another four years, or two salmon generations, if the infestations continue.
The impact is so severe that the viability of the wild salmon populations is threatened, says lead author Martin Krkosek, a fisheries ecologist from the University of Alberta. Krkosek and his co-authors calculate that sea lice have killed more than 80% of the annual pink salmon returns to British Columbias Broughton Archipelago. If nothing changes, we are going to lose these fish.
Previous peer-reviewed papers by Krkosek and others showed that sea lice from fish farms can infect and kill juvenile wild salmon. This, however, is the first study to examine the population-level effects on the wild salmon stocks.
It shows there is a real danger to wild populations from the impact of farms, says Ray Hilborn, a fisheries biologist from the University of Washington who was not involved in the study. The data for individual populations are highly variable. But there is so much of it, it is pretty persuasive that salmon populations affected by farms are rapidly declining.
According to experts, the study also raises serious concerns about large-scale proposals for net pen aquaculture of other species and the potential for pathogen transfer to wild populations.
This paper is really about a lot more than salmon, says Hilborn. It is about the impacts of net pen aquaculture on wild fish. This is the first study where we can evaluate these interactions and it certainly raises serious concerns about proposed aquaculture for other species such as cod, halibut and sablefish.
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