Influence of Acclimation Temperature on Preferred Temperature in the Rainbow Trout Salmo gairdneri

The relation of preferred temperature to acclimation temperature of 29 rainbow trout 15 months old was examined during summer. Fish were acclimated to 5, 10, 15, 20, and 25 C, respectively, and tested individually in an electrically controlled shuttlebox device. Body temperatures monitored by a radiothermometer ingested by the fish closely approximated occupied temperatures to within 0.2 C. No significant differences were found in preferred temperature over the acclimation range studied. The calculated final preferendum was 11.3 C. Fish regulated environmental and body temperature with the same precision as they selected temperature in a spatial gradient.