Research Document 1998/93

Estimating the percentage of hatchery-reared juvenile coho salmon in the Strait of Georgia in 1997

By R.J. Beamish, R. Sweeting, and Z. Zhang

Abstract

The marking of a large number of hatchery coho in 1997 by removal of the left pelvic fin provided an opportunity to estimate the percentage of hatchery and wild coho in the Strait of Georgia. The survey of juvenile coho abundance and distribution in the Strait of Georgia and Puget Sound in 1997 provided samples that enabled estimates of hatchery and wild coho to be determined prior to any fishery. These marked coho and catches from surveys in June/July and in September indicated the proportion of juvenile hatchery coho within the Strait of Georgia ranged from 76-79%. If estimates of smolts from enhanced adults (i.e., hatchery fish spawning in the wild) were included as hatchery releases, estimates of hatchery percentages in the catch could be as high as 87%. Both hatchery and wild juvenile coho remained within the Strait of Georgia until after September, several months after coho left Puget Sound. There was no difference in the length of coho with or without the left pelvic fin

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