Freshwater life history of chinook salmon (oncorhynchus tshawytscha) in the rangitata river catchment, new zealand

Abstract

Migration and residence of chinook salmon in the Rangitata River and 1 of its tributaries (Deep Stream) were investigated during 1983–85, and compared with findings from similar studies undertaken in the nearby Rakaia River catchment during 1972–84. The estimated spawning population (±95% confidence interval) in Deep Stream was 748 ± 161 in 1983, and 1071 ± 147 in 1984. The seasonal timing of adult and juvenile movements in and out of Deep Stream was similar to that in Glenariffe Stream, a Rakaia River tributary, as was the development of a population of resident juveniles in spring and early summer. Juvenile salmon biomass in Deep Stream from October to March averaged 0.31 ± 0.14 g m−2. During peak fry migration, juvenile chinook salmon were found throughout the Rangitata mainstem, although only in the upper reaches was there evidence of extended freshwater rearing. Juvenile salmon migration from Deep Stream appears to be less influenced by competition for rearing habitat than in Glenariffe Stream, suggesting that differences may exist between the egg to fry survival and/or rearing capacity in the 2 streams. © Crown copyright 1989.