Swimming Ability of Fish

Abstract

A method to deal quantitatively with swimming ability of fish was investigated. Duration of swimming [swimming time: t (sec)] was measured at various current velocities [swimming speed: V (cm/sec)]. The relationship between swimming speed and swimming time presented a curve, “swimming curve”, and was expressed by the following formula: V·tk=a where k and a are constants peculiar to any one species and its growth stage. Swimming ability was assumed to be proportional to the total swimming time a fish could maintain itself against various current velocities. Therefore, swimming ability index (SAI) was defined as follows: [formula omitted] SAI may be considered as the synthetic index of swimming ability. Both cruising speed and burst speed have been used as the index for the estimation of swimming ability, but they are not sufficient to estimate swimming ability synthetically. SAI should be used for the accurate estimation of swimming ability of fish. The values of SAI were obtained for 16 species by means of swimming tests. The values of SAI of Plecoglossus altivelis and Salmo gairdnerii irideus were high and those of Anguilla anguilla and Misgurnus anguillicaudatus were low. The values of SAI of P. altivelis were also obtained and discussed for the different growth stages. © 1975, The Japanese Society of Fisheries Science. All rights reserved.