Determination of stages of sex maturity of Rutilus frisii kutum Kamenskii, 1901 in the Caspian Sea using biological indexes

The Caspian sea as a unique habitat has accommodated Rutilus frisii kutum for as long as the course of history but has undergone extreme ecological & managerial disturbances over the recent centuries which has in turn, borought about dire consequences including the formation of a potentially fragile ecosystem. In fact, various researches undertaken on this issue has shown that the specter of such ominous changes in ecosystem and the living resources of the Caspian Sea loom near. The present study aims at investigating the sexual and biological aspects of fish &their sex organs in Rutilus f. Kutum along the southern coasts of the Caspian Sea. To this end, the fish and gonad samples of Rutilus f. kutum migrating to rivers & estuaries were collected & analyzed through sampling procedures based on fish gonad. Upon treating the samples with Bouin & the related preparations, (I.e. extraction of water, making from the sample them transparent, molding & doing them based on H&E method),, whereas Peterson correlation coefficient was applied for toxic variables. The results of the analysis shows that 45 percent of sampled fish with an average length of (349 58) mm weighing 564 334) were male and 54.4 were Females. The sexual maturity rate, as specified by the six stages analysis me Thad of Johnson’s (Johnson’s, 1970) in dictated the position of female in the stages: IV & V during March, April & June. 32% of female fish were in stage V & %68 in stage IV in March whereas the percentages of female fish in April was %87 in the stage V followed by %94 in the stage V during June.