Stream residence time, size characteristics, and migration patterns of juvenile chinook salmon (Oncorhynchus tshawytscha) from a tributary of the Rakaia river, New Zealand

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Abstract
The downstream migration of juvenile chinook salmon in Glenariffe Stream, a tributary of the Rakaia River, South Island, New Zealand, is described, based on data collected between 1966 and 1981, and in particular over the period 1973–1976. The migration is characterised by large numbers of newly emerged fry in August, September, and October, followed by greatly reduced numbers of larger juveniles in November, December, and January which have reared within the stream. Total migration ranged from 275 000 in 1973 to 3 732 000 in 1976, with emergent fry accounting for 91–98% of the outmigrants. Availability of spawning gravel does not appear to be a limiting factor, but the maximum rearing capacity of Glenariffe Stream is estimated as c. 90 000 fingerlings, and it is suggested that intense population pressure within Glenariffe Stream contributes to the high proportion of emergent fry leaving the system. The relation between juvenile outmigration and subsequent adult returns is examined. Comparisons are drawn between the behaviour of juvenile salmon in Glenariffe Stream and in a number of North American systems.