Assessing spawning behavior at the northern latitudinal extreme of Pacific halibut

Many species have reduced reproductive potential at the poleward extreme of their range, where they exhibit unique spawning dynamics. However, recent poleward range expansions have resulted in many species being unstudied in these regions, such as the Pacific halibut ( Hippoglossus stenolepis) in the northern Bering Sea (NBS). To characterize Pacific halibut spawning dynamics at the northern extreme of their range, we attached pop-up satellite telemetry tags to large females in the NBS, with time series data and tag reporting locations being used to infer spawning behavior and to identify occupied spawning habitat conditions, location, and timing. Pacific halibut in the NBS occupied spawning habitat later and farther north than previously described, where spawning habitat was occupied from January to May and reached as far north as the Russian continental shelf edge. Additionally, 42% of mature individuals never occupied presumed spawning habitat, suggesting the presence of skip spawning behavior. These findings suggest that Pacific halibut exhibit unique spawning dynamics in the NBS, which may result in a reduced reproductive potential within this northern population component.