Effects of spawning temperature on the reproductive characteristics of walleye pollock Gadus chalcogrammus

Abstract

Reproductive characteristics under different water temperature regimes were examined in hatchery-reared walleye pollock Gadus chalcogrammus. The fish had been cultured for 33 months post-hatching before the experiment, and the first spawning was observed from 24 to 27 months post-hatching. From 33 months post-hatching, fish were cultured at three temperature regimes (2, 5, and 8 °C), and spawning was observed from 36 to 39 months post-hatching. The peak of the spawning period was earliest at 8 °C and latest at 2 °C, and a 3 °C difference resulted in the 2–5 weeks difference in the peak spawning period. Thus, high temperature would have accelerated gonadal maturation. In contrast, the effect of temperature on the egg quality was unclear. Egg diameter was largest at 5 °C, followed by 2 °C and 8 °C, but the starvation tolerance of larvae was not significantly explained by spawning temperature. These results elucidate the mechanisms that underlie variability of the spawning period and the larval survival of wild walleye pollock.