Seals and sea lions in the Salish Sea are all part of a healthy food web

We should be very cautious about predicting that a seal cull would benefit Chinook salmon. Food webs are not so simple.

Since the killing of seals and sea lions ended in the 1970s, pinnipeds in the Salish Sea have been recovering. The recovery of seals slowed by 2000 and for the last fifteen years or so the number of seals in the Salish Sea has been relatively stable. This population of fish eaters has recovered to what was likely historic levels.

Pinnipeds, such as seals and sea lions, are not affected by the low Chinook salmon numbers the way that the Southern Resident killer whales are because Chinook are only a small proportion of their diet.

Pinnipeds also predate on other predators of Chinook, like hake and pollock. So killing seals and sea lions to reduce Chinook predation could actually destabilize the food web and result in an increase of other Chinook predators.

Killing seals could also impact the Salish Sea’s most effective pinniped eater, transient killer whales. There are often more transient killer whales (marine mammal eaters) in the Salish Sea at any one time than there are Southern Residents (salmon eaters). Transient (Biggs) killer whales are very efficient predators, especially on seals. These whales can travel great distances to “munch on pinnipeds” in the Salish Sea.

Listen to Misty MacDuffee and Adam Stirling discuss the downsides of removing pinnipeds from the foodweb, the distinction between culls and harvests, and the measures that should be addressed before considering killing seals as a solution to rebuilding Chinook.

 

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