Application of ultrasonography to non-invasive sexing based on the sexual dimorphism in gonads of immature barfin flounder verasper moseri

Abstract

An ultrasonographic technique for non-invasive sexing of barfin flounder Verasper moseri was established based on sexual dimorphism of gonadal appearence. We used here a high frequency transducer (10 MHz) attaching to ultrasonography to improve echoic images. Although gonads of 23-month-old males were impossible to discern, those of females were visible as bright oval contours in the ultrasonographic images. Accurate identification of sex was accomplished in 63 fish ranged from 204 to 274 mm in total length of 14-month-old fish, 288 to 401 mm of 19-month-old fish and 252 to 370 mm of 23-month-old fish, except for three false diagnosis. On the other hand, it was difficult to determine sex in 11-month-old fish, 98-135 mm in total length, by this technique. The present results indicate the practical usefulness of ultrasonography for a rapid, non-invasive and realtime sexing of immature flounders.