Migration Characteristics and Hatchery Returns of Winter Steelhead Volitionally Released from Cole Rivers Hatchery, Oregon

Abstract

Juvenile winter steelhead Oncorhynchus mykiss from four brood years were reared at Cole Rivers Hatchery on the Rogue River and were released from raceways each year either by volitional migration from 1 April to 16 June or by forced eviction during 21–26 April. The date of maximum volitional migration was 4 May ± 7 d. Recapture of “half-pounders” (the small immature steelhead that enter the river in the summer and fall, after 2–6 months at sea) was not significantly different between the two release groups, but fewer adults returned to the hatchery from groups that had been volitionally released than from groups that had been forced from the raceways. No significant difference in average adult size or life history composition at each return age was found between the two groups.