Intra-seasonal and inter-annual patterns in the demographics of sand lance and response to environmental drivers in the North Pacific

Sand lance and sand eels (Ammodytes spp.) are a critical component in all northern latitude pelagic ecosystems. They are primary forage species for marine birds and mammals, target stocks for commercial fisheries in Europe and Asia, and prey to nearly all commercial fishes in the North Atlantic and North Pacific oceans. Throughout their range, there are significant knowledge gaps in the status of populations, stock structure, and life history. Our analyses of Pacific sand lance Ammodytes personatus in the fall season provide insight to life history attributes, demographic patterns, intra-seasonal trends, and response to climate forcing. We document a seasonal shift from pelagic foraging to winter dormancy, coincident with reductions in light, temperature, and a shift from upwelling to downwelling. Intra-seasonal and inter-annual trends in relative abundance and body condition demonstrate a response to regional climate indices as well as local environmental conditions, particularly evident in the context of recent North Pacific anomalous warming. We provide new insights into life history patterns, including a shift from nearshore to deep water benthic habitats as a function of age. Inter-annual patterns in size structure and juvenile abundance suggest a regular pattern of biennial fluctuations in year-class strength. These results have implications for understanding annual recruitment and seasonal variation in availability of this important resource. Our findings expand knowledge of Pacific sand lance in the California Current and Gulf of Alaska ecosystems, with application to fisheries management, ecological interactions, and comparative analyses to other regions that host this important genus of small pelagic fishes.