Swimming Performances of Four California Stream Fishes: Temperature Effects

Abstract

The critical swimming velocity (Ucrit) of four California stream fishes, hardhead, Mylopharodon conocephalus, hitch, Lavinia exilicauda, Sacramento pikeminnow, Ptychocheilus grandis, and Sacramento sucker, Catostomus occidentalis was measured at 10, 15, and 20°C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10°C, higher at 15°C, and then decreased or remained constant at 20°C. Hitch swimming performance was lower at 10°C than at 20°C. There were no significant differences among species at 10 or 15°C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20°C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar Ucrit but hitch were significantly (by 11%) faster. We recommend that water diversion approach velocities should not exceed 0.3 ms−1 for hitch (20–30 cm total length) and 0.4 ms−1 for hardhead, Sacramento pikeminnow, and Sacramento sucker (20–30 cm TL).