Thermal limits for behavioural function and resistance-adaptation of goldfish,Carassius auratus L.

Summary Goldfish were trained to perform a conditioned avoidance response in a shuttle tank at acclimation temperatures between 10 °C and 35 °C. A high level of success (85–100%) was maintained over a relatively wide range of test temperatures, although outside this range the response was rapidly and reversibly blocked. The upper and lower thermal limits for the avoidance response were determined in goldfish acclimated to temperatures between 10 °C and 35 °C. The absolute thermal limits for the avoidance response in goldfish were approximately 3 °C to 42 °C, but the range for individuals was considerably more restricted. Increased acclimation temperature resulted in higher upper and lower thermal limits and thus constitutes a reasonable resistance adaptation. Over the lower range of acclimation temperatures the upper thermal limit showed greater mobility, whereas over the upper range of acclimation temperatures the lower thermal limits showed greater mobility. Goldfish acclimated to 5 °C and 38.5 °C exhibited very reduced % success at their respective acclimation temperatures even though they showed high % success when the same individuals were previously acclimated to less stressful temperatures. These extreme acclimation temperatures probably represent the absolute limits for chronic exposure.