熊野灘におけるイサキの成熟と産卵

概要

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The present report deals with the fishery biology of Parapristipoma trilineatum, Pomadasyidae, with particular reference to maturity and spawning habits, on 1242 individuals taken from corstal areas of Kumano-nada (Kii Peninsula, central Japan) from March 1978 to August 1979. The larger half of specimens have a pair of gonads bilaterally asymmetrical in weight. Of these, the specimens with dextral gonads dominate over the specimens with sinistral ones. The development of ovarian egg proceeds uniformly throughout the ovary. The gonad index can effectively be utilized as an indicator representing the state of maturity of ovary. The index of matured female is represented as "GI≥3". The spawning takes place from June to August. The surface water temperature in the season ranged from 23°C to 28°C. The group maturity rates of female for each age group were estimated as follows: 1-age, 0%; 2-age, 36.4%; 3-age, 86.2%; 4-8-ages, 100%. The biological minimum sizes were estimated at about 160mm for both sexes. The number of ovarian eggs larger than 0.3mm in diameter (E) was given by the following equation: E=1.49L5.00×10-7 (L, fork length in mm). The estimated number of eggs spawned (Es) was obtained by the following equation: Es=5.17L5.10×10-8.
日本水産學會の論文