Population Dynamics, Distribution and Diet of Arctic Cod (Boreogadus saida) in the Eastern Chukchi Sea

As the most abundant forage fish in the Chukchi Sea and Arctic Ocean, Arctic cod play an integral role linking plankton to apex predators and transferring energy between the benthic and pelagic realms. During August/September of 2012 and 2013, two comprehensive fisheries oceanographic standardized grid surveys were conducted with stations spaced every 30 nautical miles throughout the eastern Chukchi Sea. Arctic cod were sampled by surface trawl, bottom trawl (2012 only) and acoustic surveys. We present an overview of age-0 and age-1+ Arctic cod distribution and abundance in the eastern Chukchi Sea and examine how physical and biological (prey, predators and competitors) factors influence spatial patterns in catch per unit effort. Additionally, we present results from a simple Leslie Matrix model using updated life history parameters, and recent survey data to better understand the status of Arctic cod in the eastern Chukchi Sea. Finally, to further explore Arctic cod’s ecosystem role, we assess the ontogenetic, spatial and temporal variability in their trophic role (trophic level and diet source), using C and N stable isotopes. Linear mixed-effects models were used to detect possible variation in the relationship between body length and either δ¹³C or δ¹⁵N among water masses. Age-0 Arctic cod, which were primarily found in the northern Chukchi Sea, occupied a similar isotopic niche space in different water masses, while larger Arctic cod, occurring throughout the study region, consumed a broader diet of higher trophic level prey that varied by water mass. Specifically, Arctic cod in Pacific derived waters fed mainly on pelagic prey, while cod in Arctic waters incorporated more benthic prey. Overall, examining how spatial gradients in distribution, abundance and trophic role are linked to environmental drivers can provide insight into potential shifts with a changing climate.