Grizzly Details: Salmon Collapse Could Be Bad News for Bear

Government helicopter surveys conducted this fall along the Kimsquit River area north of Bella Coola, British Columbia, tallied below-average numbers of grizzly adults and cubs. This suggests poor salmon returns of prior years might be taking their toll on the bears, starving them of their primary prehibernation food source. "The science of it says you're going to have a density of bears and productivity of the population proportional to the salmon base," says Barrie Gilbert, a retired wildlife biologist from Utah State University in Logan.

Coastal grizzlies are a different beast altogether from their smaller interior cousins. The more salmon a male eats, the larger his skull grows; the more fish a female eats, the earlier she'll reach reproductive maturity—and the more cubs she'll have each year. The population density of grizzly bears in Alaska's salmon-rich areas runs 10 to 20 times higher than those in the sans-salmon interior of the state. The more fish in an ecosystem, the more grizzly bears that can be supported. Remove the salmon from an ecosystem and grizzly numbers drop, which is what happened over the short term when Owikeno Lake's salmon stock went AWOL in coastal British Columbia in the late '90s. "There are very few biologists who will argue that salmon aren't a key limiting factor to grizzly bear numbers on the coast," says Garth Mowat, a senior wildlife biologist with the British Columbia Ministry of Environment.

Scientific American