Determination of the spawning history of Pacific saury Cololabis saira from rearing experiments: Identification of post-spawning fish from histological observations of ovarian arterioles
2016
Suyama, S. (Tohoku National Fisheries Research Institute, Fisheries Research Agency Japan, Hachinohe, Aomori (Japan). Hachinohe Station) | Shimizu, A. | Isu, S. | Ozawa, H. | Morioka, T. | Nakaya, M. | Nakagawa, T. | Murakami, N. | Ichikawa, T. | Ueno, Y.
Rearing experiments under controlled temperature conditions were carried out to establish a methodology for estimating the spawning history of the Pacific saury Cololabis saira. The experiments involved histological examination of ovarian arterioles at various maturational stages. We found that pre-spawning immature fish lacked Victoria blue (VB)-positive arterioles in the ovaries, as did maturing fish, while post-spawning females had VB-positive arterioles. The latter were also observed after 6 months when most spawning activity had ceased. The results indicate that VB-positive ovarian arterioles are a characteristic feature of actively spawning Pacific saury and that females with VB-positive arterioles can be classified as post-spawning fish. Females without VB-positive arterioles can be regarded as 'practically unspawned' fish, and this group may include some fish that have spawned a number of times, in addition to completely unspawned fish. The methodology has many practical uses such as in the estimation of maturation rates for stock management.
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