Study of the sexual maturation time in different species of the genus Neogobium(Knipowitschia caucasica) in Gomishan wetland.

The reproductive biology of the genus Knipowitschia caucasica was examined from Gomishan wetland a period of one year (2006-2007). Some reproductive characteristics like، number of undifferentiated، previtellogenic stage، vitellogenic stage and postvitellogenic oocytes، and GSI index were examinedThis 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 Knipowitschia caucasica was (p <0. 05) with respect to the numbers of differentiated and previtellogenic oocytes، and the diameter of Chorion and fulicule layers. GSI measurement showed that peak sexual maturity in this species was occurred in February.