Rose C, Nielsen JK, Gauvin J, Loher T, Sethi SA, Seitz AC, Courtney MB, Dorbny P. (2019) Survival outcome patterns revealed by deploying advanced tags in quantity (160): Pacific halibut (Hippoglossus stenolepis) survivals after release from trawl catches through expedited sorting. Canadian Journal of Fisheries and Aquatic Sciences 76:2215-2224.
Abstract
Pacific halibut (Hippoglossus stenolepis) bycatch limits many Alaska trawl fisheries and greatly concerns stakeholders from local communities and fisheries that rely on Pacific halibut. To reduce Pacific halibut mortality, Bering Sea trawlers that target flatfish have been developing expedited release procedures to sort Pacific halibut from catches earlier than current regulations allow, while continuing accurate bycatch accounting. We studied survival rates of released Pacific halibut from three trawlers by deploying accelerometer-equipped Popup Satellite Archival Tags (PSATs) on 160 fish handled under expedited procedures. PSATs recorded and transmitted two metrics indicating swimming activity for every two hours while attached to the fish for up to 60 days. Analysis of the resulting survival outcomes largely validated current survival estimation methods, based on structured viability assessments, and found longer fish length, shorter air exposure, and shorter trawl tow duration all improved predicted Pacific halibut survival. Differences in these results were detected between vessel trips and species targeted by trawling. PSATs provided detailed data from all tagged fish, while exposing fish to conditions experienced by normal releases.