New Zealand Journal of Marine and Freshwater Research abstracts

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Stream residence time, size characteristics, and migration patternsof juvenile Chinook salmon (Oncorhynchus tshawytscha) from a tributary of the Rakaia River, New Zealand

M. J. UNWIN

Fisheries Research Division Ministry of Agriculture and Fisheries P. O. Box 8324, Riccarton Christchurch New Zealand

Abstract The downstream migration of juvenile chinook salmon in Glenariife 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 outmi-gration 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.

Keywords chinook salmon; juvenile salmon; Oncorhynchus tshawytscha; migration; stream residence; size; Rakaia River; Glenariffe Stream; salmon trap

New Zealand Journal of Marine and Freshwater Research, 1986, Vol. 20: 231-252 Received 24 May 1984; accepted 23 September 1985

PDF file of entire paper: medium quality (2537K); (scanned from paper original: notes about this process)

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