HIGHAM, T.E.; MALAS, B.; JAYNE, B.C.; LAUDER, G.V.; Univ. of California, Davis; Univ. of California, Irvine; Univ. of Cincinnati; Harvard University: Reduced pectoral fin surface area does not alter braking performance in bluegill sunfish
Many natural animal movements involve accelerating from a standstill and then stopping. A presumed correlate of improved braking performance in fish is increased pectoral fin area because most fish protract these structures as they decelerate. However, the kinematics and performance of stopping are poorly understood for most species of fish as well as most species of animals. Thus, for bluegill sunfish (Lepomis macrochirus) with complete and partially ablated pectoral fins (50% original fin area), we analyzed high speed video (200 images/s) of start-stop episodes of attacks on prey at a standardized distance from the fish (40 cm). We quantified body displacement, velocity, acceleration, deceleration, and several fin angles during each feeding event. Unexpectedly, several variables including maximum velocity and maximum deceleration (grand means 72 cm/s and -512 cm/s2, respectively) did not change significantly with reduced pectoral fin area. Furthermore, the similar braking performance was not attained by significantly altering the kinematics of the medial and caudal fins. Instead, the partially ablated pectoral fins were protracted significantly more (mean difference = 42 degrees) and with a faster average velocity of protraction. Since a behavioral mechanism was sufficient to compensate for a presumably detrimental perturbation of morphology, morphology appears less likely than behavior to be the primary constraint on braking performance for this particular task. Supported by NSF BNS 8919497 and IBN 9983003.
