Cyclic climate changes and major commercial stocks in the Arctic region

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Long‐term dynamics of spring‐spawning herring and northeast Arctic cod recruitment is reported to be in line with the several main Arctic climatic indices, such as Arctic air surface temperature (Arctic dT) and mean temperature of 200‐m water column along the “Kola Meridian” section (Kola meridian dT). Variation in the herring stock recruitment is shown to be correlate with the Arctic dT and Kola meridian dT dynamics, although the cod recruitment follows these indices with a 8‐ to 10year lag. The Russian Arctic and Antarctic Research Institute (AARI) reports that for the last 100 years Arctic dT has displayed some 60‐year regular fluctuations with maxima in the 1940s and 2000s, and suggests a descending trend in the Arctic dT in the most recent 10–20 years. Thus, in the next 10 years, commercial herring stocks are likely to decrease, whereas the cod commercial stocks are likely to increase. The walleye pollock fishable biomass in the Bering Sea for the past 35 years was shown to vary in line with the PDO (Pacific Decadal Oscillation), the main temperature index of the North Pacific. In particular, higher values of the walleye pollock fishable biomass were attributed to positive PDO anomalies, whereas the lower values of biomass were characteristic of negative PDO anomalies. Analysing both PDO and solar activity dynamics for the past 100 years, a negative PDO trend in the North Pacific may be forecast. Therefore, a gradual decrease in the fishable walleye pollock biomass is likely to take place in the next 10–20 years in the Bering Sea.