Growth of landlocked sockeye salmon (Oncorhynchus nerka) in New Zealand

Abstract

The growth of landlocked sockeye salmon in the Waitaki lakes, New Zealand, was studied from 1975 to 1984. Age and growth were determined by length frequency analysis and by back calculation of growth from annual rings laid down on otoliths and scales. Growth was also determined for fish reared at three hatcheries. Salmon resident in Lake Ohau, a large deep oligotrophic lake, grew relatively slowly. Mature fish from two to five years of age averaged 182, 224, 263, and 329 mm in length, respectively. Growth was more rapid in Lakes Benmore, Aviemore, and Waitaki, which are relatively shallow and productive hydro‐electric storage reservoirs. In Lake Benmore, mature fish from two to five years of age averaged 243, 288, 352, and 450 mm in length, respectively. Fish reared in hatcheries grew faster than in the wild with some averaging 382 mm at two years of age. Food supply was considered to be the principal factor influencing growth rates. The fish originated from anadromous ancestors in the Frazer River, Canada, and have been resident in fresh water in New Zealand for about 18 to 25 generations; they retain the capacity for rapid growth in favourable environments.

Keywords:

• Oncorhynchus nerka
• sockeye salmon
• kokanee
• age
• growth
• otoliths
• back calculations
• Waitaki River
• Lake Ohau
• lake Benmore
• Lake Aviemore
• Lake Waitaki