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 Colorado squawfish Ptychocheilus lucius at 10, 14, and 20 degree C. Fatigue velocity (velocity at which 50% of the fish failed to sustain swimming in 30-min tests) increased significantly with water temperature and fish length. Differences in swimming ability between 10 and 14 degree C became less pronounced as fish length increased, but differences remained substantial between the two cooler and the 20 degree C swimming experiments for all size-classes tested. We conclude that cold hypolimnetic releases from hydroelectric dams can significantly reduce prolonged swimming ability of young-of-year Colorado squawfish, and may help explain the decline of this species in the Colorado River basi