Speed and Stamina in Three Fish

1. Measurements of the maximum speed sustained during bursts of swimming of up to 20 sec. duration by dace, trout and goldfish of various lengths are reported. 2. The ability to sustain periods of swimming appears to be related differently to length in different species. In the dace it is proportional to L 1.09, in the trout and goldfish to L 0.65 2. The ability to sustain periods of swimming appears to be related differently to length in different species. In the dace it is proportional to L 1.09, in the trout and goldfish to L 0.65. 3. The dependence of this relationship upon various factors is considered. It is concluded that allometric increase of muscle and the influence of an increasing Reynolds number, possibly combined with other, physiological, factors could adequately account for the variation observed. 4. The precise form of the speed/duration relationship differs in different species. These variations are also probably accountable for by a combination of different muscle percentages and fineness ratios together with other, physiological, factors. 5. The ability to maintain speed diminishes rapidly with increasing time interval in all the species measured. The maintained speed falls from about 10 L /sec., maintainable for only 1 sec. of swimming, down to 5 L /sec. for 10 sec. and further to a cruising speed of about 4 L /sec. by 20 sec. The nature of this time/speed relationship is considered to be determined by the ability of the muscle to utilize stores of raw material and by the rates at which these can be supplied to, and waste products removed from, the muscle. 6. A diagram showing the relationship between velocity of water flow and the maximum distance which various hypothetical fish could traverse in such currents is constructed; and possible applications of this information are briefly considered.