Hydroacoustic methods for assessing trawl catchability and fish responses to the vessel’s noise field during surveys

Methods of using stationary and mobile hydroacoustic devices for measuring fish distribution and density in different zones of the vessel-trawl accounting fishing system have been developed. Experimental estimates of the characteristics of the spatial distribution of walleye pollock and the avoidance response to the vessel’s noise field have been obtained. Measurements of depth-differentiated walleye pollock catchability coefficients have been made as part of the vessel-trawl accounting system, which summarize the avoidance of vessel noise by fish and the efficiency of the trawl itself. A model of fish movement behavior in the vessel’s noise field has been developed. Integrating this model into the algorithm of echo integration and trawl surveys will allow estimating the initial structure and spatial distribution (density) of catchable aggregations, thereby allowing for more accurate stock assessments.