Ultrasonography for sex determination of Lebranche mullet

Ultrasonography has been increasingly used in aquaculture breeding programs for non-invasive determination of sex and the gonad maturation stage in fish. For the first time, this image exam was performed on a mugilid (Lebranche mullet). Nineteen male and 12 female fish were submitted to this evaluation, which were selected because they were identified to be in the final gonad maturation stage, which was previously confirmed through spermiation by abdominal pressure and ovarian sampling biopsy (oocytes of 626 ± 12 μm), respectively. The ultrasound images were obtained after anesthesia, using a linear multifrequency probe at the frequency of 8 MHz in females and 10 MHz in males, which revealed significant differences in echogenicity between the gonads. In males, the testes presented a hypoechoic and homogeneous aspect, while in females the ovaries had a hyperechoic appearance and granular echotexture, compared to adjacent body structures. The scanning time for sexual identification and characterization of reproductive system structures in each fish was 2.58 ± 1.68 seconds for males and 2.40 ± 1.05 seconds for females, there was no significant difference (p > 0.05) in relation to sexing time. Thus, the identification of the sex of the Lebranche mullet (Mugil liza) through ultrasonography proved to be an effective, fast and non-invasive method when applied to fish with mature gonads during the species’ reproductive period.