The Effect of Low Temperature on the Early Life Stages of the Walleye Pollock, Gadus chalcogrammus—A Laboratory Study

The walleye pollock Gadus chalcogrammus is an important commercial species in Japan whose larvae and eggs may be negatively affected by the cold water mass from coastal Oyashio current that present spawning ground of Japanese Pacific stock this species. Therefore, we investigated egg larval specific density, mortality, behavioral response to temperature change during ontogenetic development understand effect surface (<1.5 °C). Egg density varied but were lower than corresponding values waters. Within our study range (0.3–10.0 °C), number days 50% mortality (D50) was high at 3.1 °C. Below above temperature, D50 showed a decreasing trend. Regarding response, 1.5°C 5.0°C, newly hatched occurred abundantly layer, irrespective rearing temperatures. When these released into thermally stratified column (surface: 1.5 °C, bottom: 5.0 reared °C with mouth open yolk sac completely absorbed moved layers. However, remained layer. These results suggest could affect survival limit escape ability unfavorable conditions.