Age, reproduction and migration of blue shark [Prionace] in the north Pacific ocean
1994
Nakano, H. (National Research Inst. of Far Seas Fisheries, Shimizu, Shizuoka (Japan))
The life history of blue shark is discussed, including age, growth, reproduction and migration. Age and growth of blue shark embryos to adults were analyzed using length frequency data and vertebra samples. Using the values of modes from the length frequency graph and calculated length from the rings of vertebrae, a von Bertalanffy growth curve was estimated for each sex. The measurements of reproduction organs were used for analyzing size at maturity and reproduction cycles of blue sharks. The males and females reach maturity at a body length of 130 to 160cm and between 140 and 160cm, respectively. The biology of blue shark pregnancy was described. The migration of blue sharks in the North Pacific was explained analyzing sex ratio in each area, distribution of each sex, and length class data from 29,161 blue sharks. Based on these observations, a schematic blue shark migration model was made in the North Pacific
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