Gait transition speed, pectoral fin‐beat frequency and amplitude in Cymatogaster aggregata, Embiotoca lateralis and Damalichthys vacca

Abstract

Surfperches are labriform swimmers and swim primarily with their pectoral fins, using the tail to assist only at higher speeds. The transition, from pectoral to pectoral and caudal fins, occurs at a threshold speed that has been termed physiologically and biomechanically ‘equivalent’ for fishes of different size. The gait transition (UP‐C) of Cymatogaster aggregata occurred at a higher speed (measured in bodylengths s−1) for smaller fish than larger fish. At UP‐C, pectoral fin‐beat frequency was size‐dependent: smaller fish have a higher pectoral fin‐beat frequency than larger fish. In contrast, at low speeds (i.e. <60% of UP‐C) the pectoral fin‐beat frequency was independent of the size of the fish. Inter‐specific comparisons of UP‐C, pectoral fin‐beat frequency and amplitude among C. aggregata, Embiotoca lateralis and Damalichthys vacca showed that C. aggregata had a higher UP‐C than E. lateralis and D. vacca. The pectoral fin‐beat frequency at UP‐C showed no significant differences among species. Cymatogaster aggregata achieved higher UP‐C, in part, through increased fin beat amplitude rather than frequency. These differences in performance may be related to the different habitats in which these species live.