Walleye pollock biomass dynamics in the Bering Sea: possibility of long-term forecasting

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This study investigates relationships between climate variations and dynamics of walleye pollock biomass in the Bering Sea. А 100-year time-series of the major climate indices were examined: air temperature in the Arctic (Arctic dT), Pacific decadal oscillation (PDO), Aleutian Low Pressure Index (ALPI), and 150-year temperature time-series of temperature changes in Gulf of Alaska (GOA SST). In addition, a 100-year series of variations in the Total Solar Irradiance (TSI) index was examined. All climatic indices and TSI show common cyclic dynamics of 60–65 year periods with peaks in the 1940s and 2000s and minima in the 1960–1970s. The overall Bering Sea pollock biomass dynamics was assessed by three major fishing regions: Donut hole area (+ Bogosloff area), West and North Bering Sea, and East Bering Sea. Each region has its own characteristics of biomass dynamics, although a comparative analysis of walleye pollock biomass changes in the entire Bering Sea and climate indices reveals their similarity. The correlation can be seen between the total walleye pollock biomass dynamics and North Pacific climate indicators (PDO and ALPI). A historical maximum in walleye pollock total biomass was observed in the mid-1980s (32 million tons), which was followed by a notable decline in biomass. The authors suggested a stochastic model to estimate long-term changes in the total abundance of the Bering Sea pollock According to the model the downward trend in the total pollock biomass will continue up to historic minimum in 2020–2030.