How do body and paired-fin positions affect the ability of three teleost fishes to maneuver around bends?

Abstract

Deep-bodied fishes with an acanthopterygian fin distribution are traditionally considered more maneuverable than fishes with a fusiform body and less derived fin positions. One measure of fish maneuverability is the ability to make yawing turns. Goldfish (Carassius auratus), silver dollars (Metynnis hypsauchen), and angelfish (Pterophyllum scalare) were induced to swim through narrow tubes bent at angles of 0°, 45°, 90°, 135°, and 180°. These three species represent a range of body form and fin position from goldfish (fusiform body and less derived ventral placement of the paired fins) through silver dollar (deep body and the same fin positions as goldfish) to the acanthopterygian angelfish (deep body and lateral pectoral fins). The minimum width of tubes through which the fish could pass a bend increased with angle for all species and among species in the order goldfish < silver dollar < angelfish. Goldfish were consistently faster than angelfish, reflecting the routine use of body and caudal fin swimming, while angelfish routinely used median- and paired-fin swimming. Greater body depth and anterolateral pectoral fin positions were not associated with greater maneuverability. Goldfish were most adept at making yawing turns in confined spaces and in such circumstances were most maneuverable.