Fig. 1. Interrelationships among selected orders of teleost fishes to illustrate variation in dorsal fin design (see Lauder and Liem, 1983). Basal teleosts (e.g. Clupeiformes and Salmoniformes) typically possess a single, soft-rayed dorsal fin (shown in red). Most acanthopterygian fishes have, in addition, a spiny dorsal fin (shown in blue) positioned anterior to the soft-rayed portion. The two fins may be either contiguous (e.g. Perciformes) or separated by a gap (e.g. Atheriniformes). In this study, we investigate the wake generated by the soft dorsal fin of Lepomis macrochirus, a representative perciform fish, to explore the functional role of this conserved feature of teleostean locomotor anatomy. Fish images modified from Nelson (Nelson, 1994).