The effect of oceanographic variability on the distribution of larval fishes of the northern Bering and Chukchi seas

Abstract

We investigated the pelagic habitat requirements of Arctic larval fish and the effects of interannual variability of ocean conditions on their distribution. We examined the distribution of larval Arctic cod, Bering flounder, yellowfin sole and capelin in the Chukchi and northern Bering seas during two years with different oceanographic conditions. We found that despite marked changes in water mass distribution, the distributions of larval fishes were not significantly different between the two years. In both years, Arctic cod and Bering flounder were found in cold, high salinity shelf waters advected from the south and influenced by winter cooling (Chukchi Winter Water and Anadyr Water mix). Yellowfin sole and capelin distributions were also similar from year-to-year but they were only found in warm, low salinity Alaska Coastal Water. The cold, high salinity water masses had elevated large copepod biomass, and the Alaska Coastal Water had elevated small copepod biomass. Thus, we propose that these water masses provided different but nonetheless potentially profitable foraging habitat for the four species of larval fishes. We conclude by suggesting that the timing and location of spawning of these species has evolved such that larval offspring are distributed in suitable foraging habitat despite interannual variability in ocean conditions. This study provides a baseline of Arctic larval fish distribution and insight into the degree of climate variability that might be expected to impact early life history stages of larval fish. Our results also increase the knowledge of the mechanistic links between oceanography and the early life history of fish. Because growth and survival of early life stages of fish often drives population change, our results contribute to the understanding of the impacts of climate change on Arctic fish populations.