Columbia River sturgeon numbers have been declining recently, and biologists don't know exactly why (see the above Oregon Field Guide video for more unsolved sturgeon mysteries). But they do know sea lions have been eating more salmon and sturgeon at Bonneville Dam over the past few years – with estimates jumping from 413 in 2006 to 2,172 this year.
Oregon and Washington biologists reported sea lions could kill as many as 10,600 sturgeon in the lower Columbia next year – including 750 spawners.
Until now, concerns about sea lion predation have focused on the impact California sea lions are having on threatened salmon populations, particularly at Bonneville Dam's fish ladders. But this month, officials sounded the alarm on a new predation problem: Endangered Species Act-protected Steller sea lions are taking an ever-larger bite out of sturgeon populations.
Because of ESA protections – which are stronger than Marine Mammal Act protections for California sea lions – the Stellars can't even be harassed (rubber bullets and sprinklers are used to shoo California sea lions away from fish).
Prospects of controlling the Columbia's sea lion problem were already dimming after a court ruling halted the program that allowed federal officials to lethally remove California sea lions to prevent salmon predation. The court questioned the program because federal agencies hadn't explained how sea lions are a threat worth killing but salmon fisheries aren't.
State and federal fishery managers say they're still hoping to ease rules on controlling sea lions on the Columbia – possibly with the help of their friends in Congress.