We’ve known for a long time that killer whales eat salmon. But new findings suggest that local orcas rely on salmon – specifically, adult Chinook salmon – more than previously thought. So now fisheries managers are having to ask themselves: What happens when endangered whales depend on endangered fish?
Because salmon are listed as threatened under the Endangered Species Act, fisheries managers have to carefully weigh a variety of factors when coming up with what’s called a “Harvest Management Plan.” That’s basically a plan that decides how many salmon fishermen can catch without harming salmon recovery. They look at how many fish are expected to return to spawn, at what times, in which rivers, and so on.
But Brian Gorman – with the National Marine Fisheries Service in Seattle -- says they’ve never factored in the killer whales’ dependence on the fish.
Gorman says doing that could mean changes in how many of the fish are left over for humans to catch.
“A possibility is that we will have to take, in the future, a much more careful look at what the relationship is between killer whales and Chinook salmon, and not just in Puget Sound.”
That’s because the orcas roam up and down the west coast, looking for salmon returning to rivers as far south as the Sacramento.
To try to get a better handle on all this, federal fisheries managers plan to convene a series of science workshops. They hope that by gathering top whale researchers from the US and Canada, they can get a clearer picture of how killer whale and Chinook populations connect.
Recent research shows that Chinook make up as much as 96 percent of the diet of the killer whale groups that call the Salish Sea home.
Scientists think scarcity of prey is one of several factors contributing to the decline of the local orca population.