The Effect of Warmer Water Temperature of Walleye Pollock (Gadus chalcogrammus) Larvae

Abstract

We examined the effect of warm temperature on the survival of larvae of walleye pollock and on their swimming behavior during the four days of post-hatch. Observations were conducted on larvae in Petri dishes and in 85 cm tall, cylindrical tanks that had a warmer upper layer and cooler lower layer separated by a small thermocline. Mortality was carried out in four temperature ranges from to . The number of days to 50 % mortality () was longest (18.7 days) at and decreased with increasing temperature to 10.3 days at . And were similar level to that at temperature 3.1 and (17.9 days). Larval responses to warmer temperatures varied depending on developmental stages. 2dph larvae changed the distribution to the thermocline of the water column. And, 3dph larvae had a ability for escaping from the unfavourable warmer temperature. These results suggest that the warmer water negatively affects the larval survival.