Swimming performances of four California stream fishes: temperature effects

The critical swimming velocity (U-crit) 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 degrees C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10 degrees C, higher at 15 degrees C, and then decreased or remained constant at 20 degrees C. Hitch swimming performance was lower at 10 degrees C than at 20 degrees C. There were no significant differences among species at 10 or 15 degrees C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20 degrees C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar U(c)rit 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).