A study published in Monday's edition of the online journal PLoS Biology found wild salmon populations are higher in rivers without fish farms than in rivers with farms.
The peer-reviewed study claims that, in rivers with fish farms, the number of migrating juvenile salmon surviving and returning to spawn declined by an average of 50 percent compared to rivers without fish farms. The study's researchers analyzed data from rivers in Atlantic and Pacific Canada and the United Kingdom.
The study was funded by the Lenfest Ocean Program, established by the Lenfest Foundation at the Pew Charitable Trusts in 2004. The study's lead author, Jennifer Ford, was a co-author of a study published last December that revealed sea lice infestations originating from British Columbia salmon farms are threatening wild salmon populations.
According to Ford's recent study, the decline of wild salmon populations in rivers with fish farms are due not only to sea lice but also to other diseases, such as infectious salmon anemia, and interbreeding with escaped farm salmon.
However, the Canadian Aquaculture Industry Alliance said the study takes a "narrow perspective on a complex issue" because there are numerous factors contributing to the decline of wild salmon populations in Atlantic and Pacific Canada.
"There are many threats and challenges facing the survival of wild salmon, such as urbanization, forestry, agriculture, mining, transportation and climate change," said Ruth Salmon, executive director of the CAIA, in a press release. "To bring it down to one issue, such as salmon aquaculture, is far too simplistic."
There is little evidence to support the theory that salmon farms increase the risk of disease in wild salmon, said Salmon, citing Canadaâ??s Department of Fisheries and Oceans.
"The Canadian aquaculture industry does not take the issue of declining wild salmon stocks lightly. We recognize the concerns of interactions with wild fish populations and work with government, scientists and others to actively address them," said Salmon. "Both wild and farmed salmon share the same environment. So it is in everyone's best interest to collaborate on preserving the health of our marine resource."
