Effect of recovery parameters on critical swimming speed of juvenile rainbow trout (<i>Oncorhynchus mykiss</i>)

Abstract

Critical swimming speed (U crit ) is commonly measured to evaluate the influence of particular parameters on the swimming ability and physiological status of fish. Prior to experiments, fish are often forced to swim at low speed for a period of time to allow them to recover from handling stress. In the past, recovery times and speeds have varied from study to study but their possible effects on U crit have not been thoroughly examined. Therefore, hatchery-reared juvenile rainbow trout (Oncorhynchus mykiss) were forced to swim at a velocity of 26.5 cm/s for 0, 0.5, 1, 2, 4, 8, or 16 h or at a velocity of 0, 17.0, 21.8, 26.5, 36.0, or 45.5 cm/s for 0.5 h prior to being subjected to the U crit protocol (5-min intervals and 2.5 cm/s increments were used). Fish were tested at 6 and 18 °C. Mean U crit values were independent of recovery time and speed at both temperatures, suggesting that the recovery phase of the protocol may not be required and that inconsistencies in U crit values among studies are probably not attributable to differences in recovery parameters used.