Turbine-Passage Mortality of Juvenile American Shad at a Low-Head Hydroelectric Dam

The immediate (1-h) turbine-related mortality of juvenile American shad Alosa sapidissima at the Hadley Falls Hydroelectric Station on the Connecticut River, Holyoke, Massachusetts, was estimated to be 0% +/- 14.5% (95% confidence interval) at the 35% wicket gate opening and 2.7% +/- 16.2% at the 100% opening. We used the HI-Z Turb\u27N tag-recapture technique, which helped minimize control mortality and maximize recapture rates. Earlier literature estimates of turbine-related mortality (up to 82%) of juvenile alosids in passage through Kaplan turbines, in our view, were substantially overstated due to either low recapture rate, high control mortality, or both