The Application of Hydroacoustic Techniques to Determine the Spatial and Distribution and Abundance of Fishes in the Nearshore Area in the Vicinity of Thermal Generating Stations

Hydroacoustic surveys of the nearshore population of fishes along the Southern California coastline have been conducted in the vicinity of thermal generating stations since 1976. A digital echo integration system was used in conjunction with Simrad EK 120 and Ross 105 kHz echo sounders. The nature of the hydroacoustic data made it far superior to net measurements of fish density because of the quantity, the speed, and the accuracy of the information collected. The hydroacoustic data revealed that significant changes in the nearshore fish density occurred between days and diel periods. This finding indicates that conventional net sampling techniques are inadequate to describe nearshore fish densities because of the length of time required for deployment of the nets. The acoustic surveys were supported by data from lampara seine catches.