TEMPERATURE EFFECTS ON SWIMMING PERFORMANCE OF LARVAL AND JUVENILE COLORADO SQUAWFISH - IMPLICATIONS FOR SURVIVAL AND SPECIES RECOVERY

We determined prolonged swimming ability of larval and juvenile Colora do squawfish Ptychocheilus lucius at 10, 14, and 20 degrees C. Fatigue velocity (velocity at which 50% of the fish failed to sustain swimmin g in 30-min tests) increased significantly with water temperature and fish length. Differences in swimming ability between 10 and 14 degrees C became less pronounced as fish length increased, but differences re mained substantial between the two cooler and the 20 degrees C swimmin g experiments for all size-classes tested. We conclude that cold hypol imnetic releases from hydroelectric dams can significantly reduce prol onged swimming ability of young-of-year Colorado squawfish, and may he lp explain the decline of this species in the Colorado River basin.