Density Dependence and Vulnerability of Fish to Entrapment by Offshore-Sited Cooling-Water Intakes

Simultaneous measurements of the offshore fish density and inplant fish entrapment ware made during eight surveys at four electric-generating stations along the Southern California coastline in 1979. Hourly estimates of the fish biomass in the vicinity of the cooling-water intake sites with state-of-the-art precision were made possible with hydroacoustic techniques. Synchronous hourly measurements of fish entrapment were made in order to describe the density dependence of fish entrapment. An entrapment vulnerability statistic, the ratio of the weight (kg) of fish entrapped in the plant (E) to the weight (kg) of fish offshore in the vicinity of the intake (B), i.e., E/B, was employed to describe the effect of water transparency, the velocity-cap and volume of flow on the entrapment of fish.