Dispersal and seasonal movements of Pacific halibut (Hippoglossus stenolepis) in the eastern Bering Sea and Aleutian Islands, as inferred from satellite-transmitting archival tags

Abstract Background Understanding connectivity is critical to the management of exploited fish stocks, but migratory dynamics of Pacific halibut ( Hippoglossus stenolepis ) in the Bering Sea and Aleutian Islands region are not well-understood. In the current study, 145 Pacific halibut ≥ 82 cm fork length were tagged with Pop-up Archival Transmitting (PAT) tags to evaluate interannual dispersal, seasonal migration, and depth-specific habitat use. Results Endpoint locations obtained after 1 year at liberty ( n = 79), fishery recoveries after 2–3 years at liberty ( n = 5), and at-liberty geopositions based on light data ( n = 5313 estimates from 109 fish) indicated geographically distinct movement patterns: Pacific halibut tagged in the Western and Central Aleutian Islands remained within the island groups in which the fish had been tagged; fish in the eastern Bering Sea remained in that ocean basin, moving among International Pacific Halibut Commission (IPHC) regulatory areas and into Russian waters; those tagged south of Unimak Pass in IPHC Regulatory Area 4A displayed the greatest amount of emigration, dispersing eastward both seasonally and interannually to as far south as Washington State. Analysis of daily maximum depth and temperature data from 113 individuals demonstrated group-level variation in summer temperatures experienced by the fish and in the timing, duration, and synchrony of movement to deep-water wintering grounds. Conclusions Depth-specific habitat use was suggestive of regionally explicit migratory contingents, while interannual dispersal patterns were consistent with the existence of multiple functional spawning units. The results may guide future research to examine cross-basin connectivity in the Northern Bering Sea and provide inputs for numerical modelling of individual movements, larval advection, and recruitment analyses.