Effects of water temperature changes on the early life stages (egg and larvae) of walleye Pollock (Gadus chalcogrammus) – Laboratory experiments and field applications

Abstract

The eastern coast of Korea (ECK) is the southern limit of walleye pollock (pollock) distribution in the North Pacific. Since the climate regime shift in the 1980s, pollock catch has decreased sharply, with <1 ton recorded annually since the 2000s. Pollock, a semi-demersal cold-water species, is greatly affected by sea surface temperature changes during its early life stages. This study analyzed the effect of different water temperatures (3.6, 5.1, 7.1, 10.0, 13.3, and 15.1 °C) on the survival and growth of fertilized pollock eggs and larvae to investigate whether the ECK is still suitable for the early life stages development of pollock. The hatching rate of eggs was 82%, 57%, and 4%, and the hatching period was 20.7, 11.6, and 5.6 d at 3.6, 10.0, and 15.1 °C, respectively. The larval size-at-hatch was the highest at 3.6 °C (5.14 mm) and lowest at 15.1 °C (4.24 mm). Above 10.0 °C, the hatching rate decreased rapidly, and the abnormality rate increased. Since the 1980s, the 10 °C isotherm in the ECK has been moving northward in winter, which is the pollock spawning season. Continuous warming of the ECK has thus been unfavorable for the early life stages of pollock. Overall, this study improves our understanding of changes in pollock abundance due to climate change.