Determination of the sexual maturation time in different species of the genus neogobium Neogobius melanostomumknipowtchia in gomishan wetland

The reproductive biology of the genus Neogobius melanostomus was examined from Gomishan wetland a period of one year (2006-2007). In the present study, one fish species namely N. melanostomus was studied, This species are as important food for economic fish species in caspian sea, specially for Acipenserid species. Different samples were taken from Gomishan wetland during one-year period of study. At this stage, the number of undifferentiated, previtellogenic stage, vitellogenic stage and postvitellogenic oocytes, and oocytes were counted. The number and diameter of ovary, nucleus and nucleolus were also measured. Data were analyzed using Systat statistical software. Results indicated that N. melanostomus was significantly different (p <0.05) with other two species with respect to the numbers of differentiated and previtellogenic oocytes, and the diameter of chorion layers. GSI measurement showed that peak of sexual maturity in this species occurred in July.