Relationships among swimming performance, behavior, water velocity, temperature, and body size for sauger Sander canadensis and longnose dace Rhinichthys cataractae

Abstract

Migration barriers and resulting habitat fragmentation are a major conservation concern for freshwater fishes. Characterizing the swimming abilities of fish is vital for fishway design and identifying potential movement barriers. The objective of this study was to assess the swimming performance of two of the most widely distributed prairie fishes, the large-bodied, large river sauger Sander Canadensis, and the small-bodied, small stream longnose dace Rhinichthys cataractae. Swimming performance for both species was assessed using a variety of metrics (passage success, maximum ascent distance, maximum sprint speed) in an open channel flume over a range of velocities (sauger, 51, 80, 93 cm/; dace, 39, 64, 78, and 90 cm/s), temperatures (sauger, 10.0, 14.3, 18.3°C; dace, 10.7, 15.3, and 19.3°C ) , and body sizes (sauger, 34.0-43.9 cm; dace, 4.6-12.4 cm). Passage success of sauger was surprisingly high (91%) over all test velocities, as was the mean maximum sprint velocity (mean, 219 cm/s). Contrary to expectations, water temperature and body size had little effect on swimming performance. Video observation showed that sauger transitioned from steady sustained swimming (aerobic metabolism) to unsteady, burst-glide or steady burst swimming (anaerobic metabolism) at 97 cm/s. Additional testing of sustained time of burst swimming by sauger in a swim tunnel (critical velocity, U sprint) showed they are capable of short term maximum bursts of 124 cm/s over a 15 second duration before fatigue. Longnose dace had high passage success in the test flume (95%) at test velocities of 39 and 64 cm/s, but success rate dropped markedly at higher velocities (66% at 78 cm/s and 19.7% at 90 cm/s). Dace swam along the bottom of the flume at all test velocities, but increased position-holding as velocity increased. Their maximum sprint velocity (139 cm/s) was about half that of sauger. Dace swimming performance generally increased with water temperature and body size.