Dispersal of Hatchery-Reared Chinook Salmon Parr following Release into Four Idaho Streams

Abstract

Repeated snorkel surveys were used to observe dispersal of parr of hatchery-reared chinook salmon Oncorhynchus tshawytscha from release sites in four mountain streams during 1994. The distribution of hatchery chinook salmon released in two streams at multiple sites was compared with the distribution of hatchery fish released in two streams at single release sites. Hatchery chinook salmon parr remained concentrated within 1.5 km of release sites through summer, but they were more evenly distributed in streams where multiple release sites were used. Densities of hatchery fish remained relatively stable following release, although there was a trend of gradual declining densities through summer and early fall.