Evaluating Pacific Groundfish Schooling Behavior and Untrawlable Refuges Using Multi-Species Mixture Models and Data from Autonomous Underwater Vehicles

Washington Sea Grant’s NOAA Fisheries Fellow spearheads development of a simulation model and sampling design, using newly developed underwater devices, to measure the abundance and improve the management of Pacific rockfishes.


James Thorson, Virginia Polytechnic and State University

Project Leader

André Punt, University of Washington, School of Aquatic and Fishery Sciences

Co-Project Leader

Ian Stewart, NOAA, Northwest Fisheries Science Center


Washington Sea Grant’s NOAA Fisheries Fellow led a team exploring the ways in which rockfish spatial behaviors affect stock assessments. The team developed a simulation model that accounts for variable schooling behavior and devised a new sampling design, using newly developed underwater sampling devices, to gather data.

Research Updates


Pacific rockfishes (Sebastes sp.) are intensively managed and in some cases listed as overfished on the U.S. west coast. Accurate stock assessments are vital to managing these species, but survey data can vary widely because of the fishes’ variable schooling behavior and deep, rocky habitats unsuited to conventional bottom trawling.


The new simulation model confirmed the improved accuracy of the mixture-distribution method the team developed for analyzing data from rockfish surveys. It also showed that inconsistent trawl efficiency across variable terrain skews survey results, but the new sampling design and data gathered with the underwater devices can correct this problem. The new mixture-distribution method is being incorporated into software tools for estimating abundance, which will be used in stock assessments of West Coast rockfish species.