Pelvic fin removal modifies escape trajectory in a teleost fish

Abstract

Pelvic fin removal has been used in mark-recapture studies and non-lethal tissue samplings; however, there is limited knowledge on the effect of fin removal on the locomotor performance in fish. We investigated the effect of pelvic fin removal on the escape response in hatchery-reared black-spot tuskfish Choerodon schoenleinii. The left pelvic fins of the tuskfish were removed, and the escape response of the modified fish was compared with control fish. The modified fish and the control fish showed C-starts that consisted of an initial bend (stage 1) and a return tail flip (stage 2). The stage 1 angle and the escape trajectory angle were greater in modified fish that turned to the side missing the pelvic fin, compared with unmodified control fish. In contrast, when the modified fish turned towards the side with the intact pelvic fin, the angles were similar to the control fish. Since both pelvic fins were extended during the stage 1 turn, it is likely that they allowed maintenance of the turning angles that determine the escape trajectory. These results suggest that pelvic fin removal has potential to negatively affect predator evasion through the modification of the escape trajectory in fish.