- 著者
-
鳥羽 光晴
夏目 洋
山川 紘
- 出版者
- 日本水産學會
- 雑誌
- 日本水産学会誌 (ISSN:00215392)
- 巻号頁・発行日
- vol.59, no.1, pp.15-22, 1993
- 被引用文献数
-
13
20
Seasonal gonadal changes were investigated by observation of oocyte diameter and histological examination in samples of Manila clam <i>Ruditapes philippinarum</i> collected from Funabashi waters in Tokyo Bay from May 1988 to September 1991. Gametogenesis was observed from January to November and gonadal maturation was bimodal, similar to southern areas of the Japanese Pacific coast, with peak periods occurring from April to June and from August to October. Gametogenesis in summer was less synchronous between individuals than in winter-spring and was characterized by the prolonged holding of a large number of matured gametes together with partial resorption and new growth of young gametes. Two annual peak periods in the condition factor, which conincided with gonadal maturation, were evident from April to May and August to September. The major spawning period of Manila clam in Funabashi waters was supposed to occur in spring, since gonadal maturation was highly synchronized and the condition factor reached its annual maximal value in this season.