Spatial distribution of arctic sand lance in the Chukchi Sea related to the physical environment

Abstract

Sand lance or sand eels (Ammodytes spp.) are small planktivorous forage fishes that play an integral role in pelagic ecosystems in the Northern Hemisphere. Arctic sand lance (Ammodytes hexapterus) is prevalent in the North Pacific in the Sea of Okhotsk, northern Bering Sea, Chukchi Sea, and Beaufort Sea. Few studies have focused on this species despite its critical position in energy transfer and trophic food webs. Recent surveys in the Chukchi Sea and Beaufort Sea have noted an increase in the prevalence of this species in concert with reduced ice extent. Sand lance are unique among forage species in having close associations with specific water column conditions as well as a reliance on specific sand substrates for burrowing. Life history and habitat dependency is influenced by both dynamic oceanographic conditions and static benthic substrata. This taxa, therefore, provides a unique opportunity to examine the potential expansion of a boreal species into Arctic marine habitats. We use comprehensive surveys conducted throughout the Chukchi Sea shelf over multiple years to evaluate spatial distribution and abundance relative to oceanographic variables in the water column and sediment composition on the seafloor. We applied logistic regression and generalized additive models to investigate presence and relative abundance of Arctic sand lance and to evaluate spatial distribution, as a function of oceanographic and benthic environmental variables. Spatial distribution shifted considerably between years in response to environmental conditions. Arctic sand lance presence was influenced by surface water mass and positively associated with Alaskan Coastal Water. Relative abundance was positively associated with high surface temperature, low surface salinity, and coarser substrates. Evidence is mounting that the distributions of many boreal species are expanding on the margins of the Arctic. Our research reports increased aggregations of Arctic sand lance in the Chukchi Sea and at the highest latitude on record for this species, at the shelf break of the Arctic Basin.