Functional design and burst-and-coast swimming in fishes

Abstract

A simple hydromechanical model is employed to determine the influence of overall body form on intermittent (burst-and-coast) swimming in fish. The optimum fineness ratio with respect to maximizing the distance covered per burst-and-coast cycle for given volume, mass, initial, and final velocities is about 5. Frequent burst-and-coast swimmers (e.g., Gadidae, Clupeidae) are characterized by fineness ratios of 4.0–6.5. Forms of low fineness ratio (< 2, e.g., Tetraodontidae, Diodontidae) do not swim in the burst-and-coast mode. The current view that fish are optimally designed for either high steady or unsteady swimming performance is questioned. It is suggested that the body form of many pelagic and nektonic fishes reflects a compromise appropriate for good burst-and-coast swimming performance.