Hydroacoustic Surveys for Thermal Plume Effects

Hydroacoustic sampling was used to provide a synoptic view of the distribution of pelagic fish targets as related to the distribution of excess temperatures from an electric generating facility’s thermal discharge under summer and fall conditions.  Initially, the aquatic habitat near the discharge was mapped using hydroacoustic technology in areas potentially inside and outside the area of thermal influence to describe bathymetry and aquatic habitats in the study area.  Mobile hydroacoustic surveys were conducted in September and November concurrently with shipboard thermal surveys.  A midwater trawl and variable-mesh gill nets were used to support the hydroacoustics data by identifying species that comprise the acoustic targets, and to characterize the species and size composition of the pelagic fish community present within the study area at the time of the surveys.  The surveys were used to produce geo-referenced maps of concurrent water temperature, fish distribution, and substrate habitat.