SAN FRANCISCO (KCBS RADIO) – The management of California's salmon population could be key to keeping the struggling species of Pacific Northwest orcas alive.
The salmon-eating Southern Resident killer whale population is dwindling, and their ability to thrive may be dependent on the availability of their key source of food, the Chinook salmon, according to a new study.
"We are only talking about the population of about 75 individuals," said, Fanny Couture, a marine ecologist and Ph.D. candidate at the University of British Columbia and the lead author of the study.
"Which is very small and it makes this population highly vulnerable to a change in any of the environmental variables that they rely on," she said.
The study examined the eating habits of the endangered group from 1979 to 2020, and how the fluctuating population patterns of the Chinook salmon may have affected the whale population in the Salish Sea and the West Coast of Vancouver Island.
According to the study, the abundance of Chinook salmon between the ages of 4 and 5 "are significant predictors of energy intake for SRKW," said the study.
In the last 40 years, the percentage of the whales' diets consisting of salmon originating from the Columbia River has increased by about 34%, and decreased by about 15% for Chinook salmon stocks originating from Puget Sound.
A diminishing food supply can have dramatic consequences for this small group of whales.
"The whales were limited by food for about six of the last 40 years," said Couture. "And this is a pretty significant number when we're talking about such a small population."
The salmon they rely on as part of their food supply does spawn in California. But it is too soon to say if the state needs to enact more rigorous protections for salmon fishing.
The next step is to take a closer look at how much salmon the whales consume in the winter months.
"Once we have the answer to these questions, we will be able to give answers in terms of what can be done for the Chinook salmon in terms of management," she said.
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