Arctic cod (Boreogadus saida) hatching season and growth rates in the Bering, Chukchi and Beaufort seas

Abstract

Arctic cod is an important prey species in Arctic marine ecosystems that provides efficient energy transfer from producers to consumers in the food web. Arctic cod are locally abundant throughout the Arctic, though little is known about their early life stages in the Pacific Arctic, especially when and where they spawn and hatch. This study estimated hatch dates and growth rates of first year Arctic cod through analysis of otolith growth increments. First-year Arctic cod were captured in the northern Bering, Chukchi, and Beaufort seas during the spring or summer between 2012 and 2017. Estimated hatch dates ranged widely from November to June with peak hatching occurring from February through May, depending on the region of capture. Combined with large individual and regional variability in growth rates, this suggests a bet-hedging strategy to ensure some larvae encounter favorable growth conditions. In addition to regional differences, we identified a clear separation of hatch dates between spring- and summer-caught Arctic cod in the Chukchi Sea, suggesting different origins or strong size-dependent mortality. Finally, differences in hatch dates between pelagic and demersal juveniles indicate that older, larger juveniles begin to settle to the seafloor on deeper portions of the shelf in late summer. The results of this study set a benchmark for Arctic cod early life history in these regions and provide context for monitoring early life stages in a changing environment.