Brown Bear Predation on Sockeye Salmon at Karluk Lake, Alaska

Publication Type:Journal Article
Year of Publication:1971
Authors:Gard, R
Journal:The Journal of Wildlife Management
Volume:35
Date Published:1971
ISBN Number:0022541X
Keywords:Ursus arctos
Abstract:

Effects of predation by brown bears (Ursus arctos) on sockeye salmon (Oncorhynchus nerka) were studied at Grassy Point Creek, a tributary of Karluk Lake on Kodiak Island, Alaska, during the summers of 1964 and 1965. In 1964 bears were allowed free access to the stream, but in 1965 an attempt was made to exclude them with an electric fence. Bears were efficient predators in the stream, killing up to 79 percent of the salmon in 1964; however, only 9.6 percent of the dead females sampled were unspawned bear-killed fish. The maximum estimate of eggs lost to bear predation in 1964 was about 1 million, compared with a total loss, from all causes, of 8 million potential eggs. As a result of certain behavioral patterns of sockeye salmon, bears usually take spawned-out rather than unspawned females. The ratio of males to females in each year's escapement approached 1:1; the ratio among bear kills was about 3:2. Males acted as a buffer against predation on females. The fence reduced bear predation by two-thirds. It is concluded that bear predation has little adverse effect on the production of sockeye salmon.

URL:http://www.jstor.org/stable/3799591
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