Behavioural thermoregulation and activity patterns in the green sunfish, Lepomis cyanellus.

Behavioural thermoregulation and locomotory activity of green sunfish were examined in a temporal temperature-gradient apparatus. Green sunfish actively avoided temperatures exceeding 30.3 degrees C and below 26.5 degrees C and had a median preferred temperature of 28.2 degrees C. Temperature preference did not vary significantly during the diel period even though locomotory activity patterns were markedly crepuscular. Activity was stimulated by the change in illumination levels at dawn and dusk.