The Electric Power Research Institute (EPRI) has funded laboratory studies at Alden on the biological efficacy of fine-mesh screens for safely collecting larval and juvenile fish. However, little information existed on the effects of fish return systems on larval or early juvenile survival. Alden performed two years of laboratory evaluations on factors affecting larval fish survival in fish return systems at cooling water intake structures (CWISs). The project provided the additional data necessary to determine the overall biological efficacy of larval fish collection and return systems. The study was designed to evaluate the effects of velocity, drop height, length, drops and bends on larval fish survival through a fish return system.