Effect of Temperature on Initial Feeding in Alevins of Chinook Salmon (Oncorhynchus tshawytscha)

Abstract

Growth and survival of chinook salmon (Oncorhynchus tshawytscha) during the transition to active feeding were examined in relation to the timing of initial food presentation at 6, 8, 10, and 12 °C. The transition to active feeding in these salmon involved a period of "precocious feeding" during which ingestion of food had no effect on fish size, growth rate, or survival. Initial utilization of food for growth and survival did not coincide with any specific stage of development, but rather it occurred earlier and at a less mature stage of development at higher temperatures. Delays in initial food presentation beyond this point reduced fish size and survival. Temperature and the timing of initial food presentation interacted to create a zone of optimum feeding. Biomass production was maximized when alevins began to feed within this zone, independent of the precise time of initial food presentation or temperature. This optimum feeding zone existed at temperatures below 12 °C, between 905 thermal units (tu) postfertilization and a point (F, tu) which varied with temperature (T, °C) as F = 1201.1 − 20.3 T.Key words: temperature, initial feeding, Oncorhynchus tshawytscha, fish culture