Caudal fin aspect ratio as a predictor of maximum swimming speed

The speed at which a fish can swim is determined by a combination of the movement of the muscle structure, the shape of the fish and the fins. There are three different types of swimming speeds identified in fish; sustained swimming, prolonged swimming, and burst swimming. It is generally recognised that maximum swimming speeds are the most difficult to accurately estimate. The aim of this study was to predict the maximum swimming speed using morphometrics from historical data. The maximum speeds of various teleost species were collected from a range of sources dating back to 1952. Each species was classified into a swimming mode based on Lindsay (1978) and only caudal fin swimmers were used. The documented maximum speeds were plotted against caudal fin aspect ratio and an exponential trendline was fitted. A total of 255 individual swimming speed measurements of fish species were gathered from 31 different literature sources. Anguilliform had the lowest aspect ratio with values ranging from 0 to 1.61 and thunniform had the greatest with values ranging from 5.5 to 7.9. The relationship between caudal fin aspect ratio (AR) and maximum swimming speed of 74 species from the literature was best described by an exponential equation. (y = 0.59e^0.42x, R²= 0.85). This allows us to make general predictions as to the maximum swimming speed of a fish given the aspect ratio of the caudal fin. This study’s finding can be applied beyond these species, for example, the maximum swimming speeds of fish could be utilised for the design of bycatch reduction devices or refinement of existing gears/modifications.