Differing swimming modes, methods of propulsion, and drag reducing effects account for the wide variation found among the swimming abilities of the world’s fishes (Videler 1993, Webb 1975, 1994). Most fish swim by pushing backwards against the water with undulation of their body and their fins (Lindsay 1978). Different species of fish have different swimming modes defined by variation in these body and fin undulations (Breder 1926), examples include: anguilliform where the whole body is thrown in a wave (e.g., eels); carangiform where the body and caudal (tail) fin is thrown into a wave (e.g., pike, cod, salmon); and ostraciform where the body is held rigid and the caudal fin oscillates (e.g., cowfishes, boxfishes). Fish also have different propulsion systems due to differences in body and fin morphologies, and their drag reducing features differ (e.g., mucus, skin, and scale morphologies).

The fastest swimmers are characterized by streamlined bodies that are elliptical in cross section and have a narrow caudal peduncle. Examples of these fast swimming fish include tuna, salmonids, and black basses (Micropterus sp.). Fishes that are compressed laterally, such as the sunfishes (Lepomis sp.), have well developed maneuverability and are capable of quick bursts and turns. Some of the slowest fishes have rounded bodies and use oscraciform swimming. The swimming abilities of different fishes are often reflected in their life history traits (Castro-Santos 2002, Peake et al. 1997, Swanson et al. 1998, Taylor and Foote 1991). For example, fish completing long migrations in flowing water or that spend more time in fast moving riffles have better swimming performance than more sedentary species or species that mainly inhabit pools.