On Oct. 12, the University of British Columbia issued a press release claiming that a newly published study has “debunked” the idea that there are fewer Chinook salmon available during the summer for the endangered Southern resident killer whales compared to the abundance of fish available to the Northern resident killer whales. The press release grossly overstates the findings of the referenced study. The UBC study describes a new methodology for surveying for Chinook salmon in the oceanic environment, but includes too many unknowns and is too small of a data set to come to such a broad-sweeping conclusion. A coalition of partner organizations has responded with an in-depth statement which can be found at https://orcabehaviorinstitute.org/news/joint-response/.
Numerous previous studies have shown that Chinook salmon are of year-round importance to resident killer whales, making up 83-99% of their summer diet, and that prey limitation is the primary factor contributing to the decline of the endangered Southern Resident killer whale population. Additional research shows that Southern Resident survival and fecundity are linked to Chinook salmon abundance, and body condition and survivorship are linked to Salish Sea salmon runs. The UBC study and press release do not consider the region-wide decline of Chinook salmon overall, or the fact that both Southern and Northern Resident killer whales have started abandoning core habitat as a result of prey declines.
Given the constraints of the study, the bold claim made by the title of the press release that there is “No apparent shortage of prey for southern resident killer whales in Canadian waters during summer” is a clear embellishment of the results. While we agree with the authors that to fully support Southern Resident killer whale recovery we need to look at their year-round diet from all regions, dismissing the importance of Salish Sea Chinook salmon to the whales is counterproductive to the years of research showing the importance of these runs to the whales and the ongoing advocacy to promote recovery of these salmon runs.
Orca Behavior Institute, Orca Network, Center for Whale Research, Whale Scout, Salish Sea Ecosystem Advocates, Whale and Dolphin Conservation, Wild Orca, Orca Conservancy, University of Exeter, Salish Sea School, Pacific Northwest Protectors, Salish Sea Orca Squad