Abstract
Although few studies have been conducted to directly quantify ichthyoplankton mortality at hydroelectric installations, there is a considerable body of literature on examinations of the various stresses (i.e., pressure changes, blade contact, shear) that could affect turbine-entrained eggs and larvae. A review of these studies suggests that turbine-passage mortality of early life stages of fish normally would be relatively low at the low-head, propeller-type turbine installations (e.g., bulb or STRAFLO turbines), for which relevant design information is available. The shear forces and pressure changes in low-head bulb turbines are unlikely to cause ichthyoplankton mortality. Probability of contact with turbine blades is related to size of the fish; less than 5% of entrained ichthyoplankton would be affected. Potential additional sources of mortality related to the design and operation of hydroelectric facilities, and thus mitigable, include withdrawal of deep water and cavitation.