WH A T W E H A V E L E A R N E D
Previous surveys found very high abundances of young Arctic cod on the northeast Chukchi Sea shelf, suggesting that this region is a nursery area for young fish during summer. Relatively few adult Arctic cod have been found during research surveys on the Chukchi Sea shelf during summer months, leading to questions about when and where they spawn. Arctic cod from multiple spawning times and loca- tions, likely including areas in the northern Bering Sea, Bering Strait region, and Kotzebue Sound, hatch over an extended period from November into June and are carried into the northeast Chukchi Sea by currents. They appear to remain in the Chukchi Sea during summer where they feed and grow, and are then transported northwards to the Arctic shelf break in fall. These fish are distinct from spawning popula- tions in the Eastern Beaufort Sea based on multiple lines of evidence, including differences in hatch date distributions and otolith chemistry. In the southern Chukchi Sea, adult Arctic cod were scarce near the seafloor in June 2017 & 2018. However, Arctic cod are more abundant in the same area in the summer, suggesting that adult Arctic cod could be migrating from the north where food is abundant, to the south where they may spawn. In the Beaufort Sea in the summer, young Arctic cod are grouped into east and west populations. Those groups become less distinct as fish grow in size and swimming ability.
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