2020 年 49 巻 p. 109-120
Metapenaeopsis provocatoria owstoni (Decapoda: Penaeidae) is distributed in the waters of Japan, Korea and Taiwan. There is, however, no study available on the population biology of this species to design its sustainable management and conservation protocols. We, therefore, studied for the first time its oocyte development, ovarian maturation, size at sexual maturity and spawning season using samples collected from Kagoshima Bay, southern Japan. Histological observation of ovaries confirmed seven oocyte developmental stages. This species exhibited asynchronous ovarian development, which indicates multiple spawning in a single reproductive season. Ovarian maturity stages were classified into three categories based on the developmental stage of the most advanced oocytes in the ovary: immature, maturing and mature. Females containing oocytes that either had evidence of germinal vesicle breakdown or migrating nucleus were defined as mature. The gonadosomatic index exhibited a positive but gradual relationship with ovarian maturation progression. In contrast, macroscopic staging showed a sharper relationship with histological stages of ovarian maturity, which exposed its potential as a maturity index for M. provocatoria owstoni. The size at sexual maturity was estimated to be 12.8 mm CL, and the spawning season appeared to last from April to December, with May to June being the main part.
