Saturday, May 30, 2009

Columbia River seeing record number of jack chinook

For the last two years the columbia system has been seeing unprecedented numbers of jack chinook returning. Last years return of last year during the spring run of chinook 17,683 jacks were counted passing upstream of Bonneville dam, nearly 8,000 more than the ten year average 9,968 fish. Traditionally biologists have used Jack counts to predict the following years return of adult fish. This year however that relationship appears to have broken down with a much smaller return of older fish than managers had been predicting. This year Jack counts are even higher, with more than 64 thousand jacks already past Bonneville. The sudden change in the proportion has maangers vexed and has them questioning their understanding of how the environment, as well as hatchery practices may be influencing the life histories of these fish. An article in the Seattle Times today provides some background.

Also see some discussion of how Jack counts may be throwing off managers ability to preseason forecast at the Columbia Basin Bulletin.

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