Multiple Life-Stage Connectivity Of Pacific Halibut (Hippoglossus Stenolepis) Across The Bering Sea And Gulf Of Alaska

Pacific halibut (Hippoglossus stenolepis) is managed as a single stock throughout the Gulf of Alaska (GOA) and eastern Bering Sea (BS), but biogeographical barriers and the potential for differential impacts of climate change may alter habitat use and distributions, and restrict connectivity between these ecosystems. To improve our understanding of larval dispersal pathways and migrations of young fish within and between GOA and BS, we (a) examined potential pelagic larval dispersal and connectivity between the two basins using an individual-based biophysical model (IBM) focusing on years with contrasting climatic conditions and (b) tracked movement of fish up to age-6 years using annual age-based distributions and a spatiotemporal modeling approach. IBM results suggest that the Aleutian Islands constrain connectivity between GOA and BS, but that large island passes serve as pathways between these ecosystems. The degree of connectivity between GOA and BS is influenced by spawning location such that an estimated 47%-58% of simulated larvae from the westernmost GOA spawning location arrived in the BS, with progressive reductions in connectivity from spawning grounds further east. From the results of spatial modeling of 2- to 6-year-old fish, we can infer ontogenetic migration from the inshore settlement areas of eastern BS toward Unimak Pass and GOA. The pattern of larval dispersal from GOA to BS, and subsequent post-settlement migrations back from BS toward GOA, provides evidence of circular, multiple life stage, connectivity between these ecosystems, regardless of climatic variability or year-class strength.