A temperate labrid fish demonstrates compensatory mechanisms to feed at torpor‐inducing temperatures

Temperature can have profound impacts on fitness‐related activities in fishes. Feeding is an ecologically relevant task which is controlled by muscle function. Consequently, in ectotherms, muscle function and feeding kinematics can be altered by temperature. This study investigated the effect of decreasing temperature on the feeding kinematics of the northern most labrid in the Western Atlantic. During winter, cunner ( Tautogolabrus adspersus ) enter a state of extended torpor in order to conserve energy when water temperatures drop below ~10°C. We hypothesized that feeding kinematics would be slower at lower temperatures especially those associated with torpor (≤10°C). Additionally, we hypothesized that prey type will elicit different feeding behaviors. Feeding events on sandworms and Asian shore crabs were recorded at 5, 10, 15 and 20°C. Fish held at 5°C had slower opening and closing jaw velocities while using more ram than the other temperature treatments. No differences were detected between prey types. For both prey types, the temperature treatment which consistently induced torpor (5°C) slowed oral jaw movements, which likely forced cunner to rely more on ram than suction to capture prey. Torpor temperatures appeared to have less of an effect on feeding than on metabolic rate, steady swimming capabilities and muscle function, suggesting some compensatory mechanisms of feeding musculature in cunner.