Age, growth, and movement dynamics of Arctic cod (Boreogadus saida) in the Chukchi and Beaufort seas

Abstract

Arctic Cod (Boreogadus saida) dominates fish assemblages in the Arctic and provides a valuable food source to upper trophic level predators. Little is known about several important facets of its biology and ecology in the Pacific Arctic, including in the Chukchi and Beaufort seas. The physical connectivity of these two biologically and hydrologically unique seas provides an excellent opportunity to explore differences in Arctic Cod life history characteristics such as age, growth, and movement dynamics in these two adjacent areas. To establish a current benchmark of Arctic Cod life history and movement characteristics for the Pacific Arctic, Arctic Cod otoliths collected from 2009 to 2014 during twelve research cruises conducted throughout the Chukchi and Beaufort seas were used to estimate growth and age structure for this species from the two regions. Ages of Arctic Cod ranged from 0 to 5 years with significant overlap in size at age. Growth of Arctic Cod collected in the southern Chukchi Sea and eastern Beaufort Sea regions were similar, suggesting freshwater-influenced regions may enhance growth compared to other areas. Additionally, microchemistry of age-0 Arctic Cod otoliths was analyzed to determine potential differences in elemental signatures between the Chukchi and Beaufort seas, and to infer movement between them. Otolith trace element concentrations were distinct between the Chukchi and Beaufort seas, indicating populations of Arctic Cod from the Chukchi and Beaufort seas can be differentiated based on otolith elemental signatures. Furthermore, elemental signatures from the cores of otoliths were significantly different from those from the edges in both seas suggesting early life history movement. As the Pacific Arctic faces warming sea temperatures and sea ice reduction, predicting a species-level adaptation to a changing environment is nearly impossible without establishing a benchmark for future comparison. This research will provide valuable insight into Arctic Cod across a broad portion of its distribution.