Relationships among Swimming Ability, Current Velocity Association, and Morphology for Freshwater Lotic Fishes

We determined swimming ability for 37 warmwater stream fishes in Texas and Louisiana and assessed relationships among swimming ability, habitat selection, and fish morphology. Mean absolute speeds (cm/s) were 17.8-81.9 cm/s for Cyprinidae, 50.9 cm/s for Characidae, 70.0 cm/s for Ictaluridae, 33.0 cm/s for Cichlidae, 40.0 cm/s for Percidae, 30.7-43.4 cm/s for Cyprinodontidae, 30.2 cm/s for Atherinidae, 15.7-18.6 cm/s for Poeciliidae, and 23.4-40.5 cm/s for Centrarchidae. Absolute swimming speeds were correlated (P<0.01) to reported habitat descriptions (i.e., sloughs, lakes, streams, and rivers) of fishes. Absolute swimming speeds also were good predictors of spatial (i.e., runs, pools, and riffles) distributions of fishes from Independence Creek, Texas (P=0.03), and Banita Creek. Texas (P=0.06). Multivariate ordination of nine morphological attributes identified the linear combination of relative body depth, dorsal fin length, and caudal span width as an adequate predictor (P<0.01) of swimming speed: however, several exceptions were noted. Understanding interactions between current velocity and swimming ability in fishes is critical to species conservation and to maintaining instream flow requirements for fishes.