Monitoring of Sexual Maturation in Silver Eels Using Ultrasonography

Understanding and control of eel maturation has strong interest for scientific and commercial purposes. To progress in this area, possible improvement of sex determination and maturation monitoring using ultrasonography was investigated in silver eels (Anguilla anguilla). Ninety six fish were scanned for sex determination using portable ultrasound equipment. Part of them was then subjected to artificial induction of maturation for monitoring of gonad growth at the individual level, and estimation of ovary mass and then gonadosomatic index (GSI) in females. A linear model based on estimations of gonad length and cross-sectional areas at different times of maturation was defined and used for calculation of ovary mass. Ultrasonography resulted in 100 % success in sex determination and good estimation of ovary mass (97% correlation with true values). Ultrasonography made possible the detection of early inter-individual differences in maturation in female silver eels, and has great potential for use in eel both for conservation and aquaculture.