Influence of Spawning and Nursery Ground Environmental Changes on Walleye Pollock Catches Along the Eastern Coasts of Korea and Japan After the Late-1980s Climate Regime Shift

Abstract

The eastern coasts of Korea (ECK) and Japan (ECJ) are located at the southernmost limit of walleye pollock distribution in the Northwest Pacific. Following the climate regime shift (CRS) in the late 1980s, pollock catches in these regions have declined sharply, with different trends emerging. This study examined the relationship between environmental factors, such as sea surface temperature (SST) and habitat suitability, and changes in pollock catches from the late 1980s to 2022. From the late 1980s to the late 1990s, El Niño and positive Pacific decadal oscillation (PDO) phases dominated, increasing SST in the ECK and ECJ habitats and rapidly decreasing catches. Although spawning grounds (SGs) have maintained high habitat suitability, nursery ground (NG) suitability has declined. From the late 1990s to 2022, La Niña and negative PDO phases prevailed, with SST continuing to rise along the ECK, further reducing catches. SG suitability remained high, but NG suitability declined. Along the ECJ, SST decreased after the late-1990s CRS, stabilizing catches. After the mid-2010s, the SST increased along the ECJ, reducing pollock catches, although SG suitability remained high. This study elucidates SST changes during early life stages and their effects on pollock catch, habitat, and resources in future marine environments.