Intraspecific variation in swimming- and escape performance in the labriform shiner perch, Cymatogaster aggregata

Abstract

Intraspecific variation in swimming performance, morphology and escape responses was assessed in the labriform shiner perch, Cymatogaster aggregata. Shiner perch were videotaped while swimming in a respirometer during a critical swimming speed (Ucrit) protocol. The degree of individual variation in both oxygen consumption rate (ṀO2) and kinematic performance was evaluated from this Ucrit challenge. Fast escape performance was also evaluated in the same group of fish. There was an approximately two-fold variation in metabolic rate of fish swimming at 0.5 body lengths per second (MR@0.5 bl s-1) and active metabolic rate, aerobic scope for swimming and critical swimming speed. A significant correlation was found between active metabolic rate and aerobic scope and between MR@0.5 bl s-1 and aerobic scope. Similarly there was a significant relationship between active metabolic rate and Ucrit. Individual variation in swimming performance could not be explained by differences in morphology of the caudal or pectoral fins or variation in body shape or size. There were no significant relationships between stage of escape response completed and any metabolic variables indicating that anaerobic escape responses are independent of aerobic capacity of the fish.