北海道後志沿岸におけるクロソイの年齢と成長

抄録

Age and growth of Sebastes schlegeli collected from the coastal waters of the Shiribeshi subprefecture in Hokkaido were studied. Observations of the otolith margin verified that annuli (outer margins of the opaque zone) were formed chiefly in June. This period accorded approximately with the parturition season (late May-mid-June) that was judged from the seasonal change in gonadosomatic index, occurrence of eyed eggs and histological observations of ovaries. The surface method of otolith aging was found to be inadequate for aging of S. schlegeli older than 7 years because of the underestimation of age. A significant difference was found in the parameters of the growth equations between females and males. Growth of S. schlegeli was expressed by the von Bertalanffy asymptotic growth function as TL_t=633.1(1–exp ^{-0.160(t+0.965)}) for females and TL_t=417.7(1–exp^{-0.363(t+0.368)}) for males, where TL, is the total length (mm) at age t (after parturition in years). Based on previously published data, the growth rate of S. schlegeli in this region was relatively low, especially in males, because of low temperatures during the winter and spring and the shortness of the high growth period of 10-20°C.