Sex Ratio of Marbled Sole Pleuronectes yokohamae Distributed in Harima Nada and Osaka Bay, Eastern Part of the Seto Inland Sea, Japan

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Marbled sole <I>Pleuyonectes yokohamae</I> is a commercially important flatfish in the Seto Inland Sea. The sexes of this species were examined for 6093 specimens collected from Harima Nada and Osaka Bay in May 1986 to Jan. 2001. The overall sex ratio (females/total) was 0.54, but it differed between fishing gears, months, ages and total-length classes. In the spawning season, the sex ratios in the compact trawls were higher than 0.5, while those in the gill nets were lower than 0.5, suggesting that migrations of the marbled sole differed between females and males in the spawning season. The sex ratios also varied between body sizes; fish under 240mm in total-length class had a tendency of the sex ratio to be under 0.5 and those of the over 240mm total-length classes were over 0.5. Cohort analyses simulated that the different growth patterns between the sexes could cause the difference of the sex ratio in the total-length classes. The sex ratio of the 1-age group was under 0.5 and those of the over 2-age groups were over 0.5. The sex ratio of the specimens collected by compact trawl showed no clear temporal trend in the period from 1986 to 2001.
日本水産増殖学会の論文