Steelhead and Chinook Salmon Bioenergetics: Temperature, Ration, and Genetic Effects

The bioenergetics of two anadromous native salmonid fishes in California were investigated, concentrating on effects of water temperature and ration size on juvenile Nimbus Hatchery strain steelhead (Oncorhynchus mykiss irideusy and juvenile Nimbus strain chinook salmon (Oncorhynchus tshawytscha). Nimbus strain steelhead reared at water temperatures of 11, 15, and 19°C and ration levels of 100 and ca. 87% satiation showed increases in growth rates, food consumption rates, and upper acute thermal tolerance at increased temperatures. Temperature generally did not affect steelhead oxygen consumption rates, swimming performance, or thermal preference. Ration level affected oxygen consumption rates. Juvenile Nimbus strain steelhead differ from some other anadromous and resident rainbow trout strains. Nimbus strain chinook salmon reared at water temperatures of II, 15, and 19°C and ration levels of 100 and 25% satiation showed increases in growth rates and food consumption rates with temperature. Salmon recieving the 100010 ration grew faster than those on the restricted ration at all temperatures. Salmon fed the unrestricted ration at 19°C had higher swimming performances than those fed the restricted ration; no ration dependentdifferences in upper acute thermal tolerance or oxygen consumption were observed