COOKE, SJ; STEINMETZ, J; DEGNER, J; GRANT, EC; PHILIPP, DP; Queen’s University Biology Station and the University of Illinois; University of Illinois; University of Illinois; University of Illinois; Illinois Natural History Survey: Interaction of Fish Size and Avian Predator Species on the Non-lethal Costs of Predation in Largemouth Bass

Recently, researchers have identified that non-lethal costs of predation may arise not only from lost energy intake, but also potentially from increased energetic expenditure. During periods of heightened stress following unsuccessful predation attempts, organisms may remain in altered physiological state with elevated metabolism for some time. Few studies have quantified these non-lethal energetic costs of predation. We monitored the cardiac response (cardiac output (CO), heart rate (HR) and stroke volume(SV)) of largemouth bass ranging in size from 200-450 mm to simulated avian predation attempts by great blue heron and osprey. Fear bradycardia during a 30 second predation attempt varied depending upon the size of the fish and the type of predator. The magnitude of the bradycardia decreased with increasing size of the fish, however, the disturbances were more extreme in response to osprey than to blue heron models. Maximal cardiac disturbance following simulated predation attempts by osprey were consistent among size classes of bass. The magnitude of the disturbance following heron predation attempts, however, was reduced as the size of fish increased. Size specific trends were even more extreme for cardiac recovery durations. Largemouth bass of all sizes exposed to osprey predation attempts required ~40 min for CO and HR, and ~30 min for SV to return to predisturbance levels. Although small bass exposed to heron predation attempts required recovery times similar to fish exposed to the osprey, as the size of largemouth bass exposed to the heron model increased above ~300 mm, the recovery time decreased significantly.