Ovarian maturation of Liza ramada in captivity

Abstract

ABSTRACTIntroduction: Continuous maintenance of broodstock in the captivity and the control of ovarian development are crucial for fish reprodcution, particularly when linked to mass propagation of juveniles in the hatcheries.Aim of the work: The present work was to perform a conclusive description of the maturing ovaries and recruit mature females of thin-lipped grey mullet, Liza ramada suitable for relaiable breeding in captivity.Material and methods: We used the morphological and the histological methods to describe the ovarian cycle of female mullets in captivity. Then, we will use hormonal administration to obtain the mature mullet females in captivity. Results: The ovaries of the fish cultured in freshwater, exhibit marked variation in size, weight and color accompanying the stage of maturity. During ovarian development, only one clutch of oocytes undergoes maturation. Also, six stages of oocyte development could be identified, namely primary oocytes stages, vesicles stage, primary yolk stage, secondary yolk stage, tertiary yolk stage and spawning (ripe) stage. Yolk deposition occurre during vesicles stage, primary yolk stage, secondary yolk stage and tertiary yolk stage. The ovarian development started as early-vitellogenesis when the day length (photoperiod) and water temperature began to decrease. Whereas the gradual decline of both the photoperiod and water temperatures ensure completion of ovary development. However, the ripe stage was absent in captivity, except by hormonal injection. Importantly, the injection of carp hypophyseal homogenate in combination with gonadotropin releasing hormone (triptorelin acetate) was powerful in trigger reproductive activities in mature spawners of mullet.Conclusion: Ripe oocytes are known to be prevailing in the ovaries occur immediately before ovulation. However, ripe oocytes were observed only in the females, acclimated to saline water and stimulated by hormones.