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

Deep-bodied fishes with an acanthopterygian fin distribution are traditiona lly considered more maneuverable than fishes with a fusiform body and less derived fin positions. One measure of fish maneuverability is the ability t o make yawing turns. Goldfish (Carassius auratus), silver dollars (Metynnis hypsauchen), and angelfish (Pterophyllum scalare) were induced to swim thr ough narrow tubes bent at angles of 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees. These three species represent a range of body for m and fin position from goldfish (fusiform body and less derived ventral pl acement of the paired fins) through silver dollar (deep body and the same f in positions as goldfish) to the acanthopterygian angelfish (deep body and lateral pectoral fins). The minimum width of tubes through which the fish c ould 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 sw imming, while angelfish routinely used median- and paired-fin swimming. Gre ater body depth and anterolateral pectoral fin positions were not associate d with greater maneuverability Goldfish were most adept at making yawing tu rns in confined spaces and in such circumstances were most maneuverable.