スケトウダラ卵の発生に対する水温の影響およびその浮上速度について
1984 年 50 巻 6 号 p. 937-942
詳細
1984 年 50 巻 6 号 p. 937-942
Development of walleye pollock Theragra chalcogramma eggs fertilized artificially, and their tolerance for thermal chage, were examined. In addition, upward speed and density of the eggs reared at 4°C were measured from 2 cell stage before hatching.
At 0°C-10°C, high hatching rates of 86-100% were obtained, and declined at -1°C and 13°C. The relationship between the mean days required for 50% hatching (T) and water temperature (θ) is shown by the following equation; T=31.70 exp (-0.12θ). Although the hatching rates of the eggs subjected to a thermal change from 4°C to -1°C at 2 cell stage were low (0-37%), they increased in more advanced stages of development. On the other hand, the hatching rates of the eggs subjected to a thermal change from 4°C to 0°C were high (73-97%) in all developmental stages. Mean upward speed and density of the eggs were 4.9-8.6 m/h and 1.020-1.023 g/cm3, respectively.
