Occurrence and Distribution of Adult Chinook Salmon in the New Zealand Commercial Fishery

Abstract

To characterize the marine distribution of New Zealand adult chinook salmon Oncorhynchus tshawytscha, we analyzed data on chinook salmon taken off the South Island east coast as a bycatch of a commercial fishery dominated by bottom trawling on the continental shelf and slope in depths up to 1,000 m. Chinook salmon, widely but sparsely distributed out to depths of 100 m throughout most of the year, showed a strong tendency to concentrate off Banks Peninsula (latitude 43°45′S) in midsummer (December–February). Of 161 metric tons taken between 1984 and 1988, 151 metric tons were taken by larger trawlers capable of towing nets with 6-m headline heights at speeds of up to 6.5 km/h. Most chinook salmon caught at sea were maturing adults returning to nearby rivers, such as the Rakaia, rather than immature fish associated with the oceanic phase of their life cycle. The low incidence of immature fish and the lack of data for offshore waters preclude any definitive conclusions about the extent to which chinook salmon travel offshore, but our results are consistent with their northern distribution being bounded by subtropical water north of about latitude 43°S and their eastern distribution being bounded by cold, low-productivity sub-Antarctic waters.