Application of hydroacoustic technology to marine fishery management in Washington State

Abstract

The Washington Department of Fisheries has utilized hydroacoustic stock assessment techniques since the early 1970s for research and management of state marine fish resources. The objectives of these applications have been to provide estimates of harvestable biomass, which drive in-season management of Pacific whiting ( Merluccius productus) and Pacific herring ( Clupea harengus pallasi) in Puget Sound, and to develop a new assessment technique for estimation of the population of black rockfish ( Sebastes melanops) off the coast of Washington and Oregon. During the early years of hydroacoustic assessment, there was considerable uncertainty from a manager's perspective concerning biomass estimates because of inconsistencies with the electronics, lack of target strength verification, inadequate data for determination of species and fish age composition, and inconsistent sampling designs. Continued improvements in methodology and equipment have resulted in better estimates of biomass which have substantially reduced the risk of making poor management decisions for herring and whiting. Because the sport and commercial line fisheries for black rockfish off the coast of Washington have emerged in recent years, estimates of harvestable biomass of this nearshore semi-pelagic species have been required for purposes of conservation and allocation between user groups. Results from the first 3 years of a 5 year project to develop a hydroacoustic survey plan have resulted in a coastwide bottom habitat map and characterization of fish distribution and densities. However, methodology for identification of species composition must still be developed before the population size of black rockfish can be estimated and applied to management.