Ovarian development trend in Kutum (Rutilus frisii kutum Kamenskii, 1901) during spawning season from Southwestern of Caspian Sea, Guilan province (Bandar-e Kiashahr)

Studies were conducted on the changes occurring in the ovaries of adult female Kutum, (Rutilus frisii kutum Kamenskii, 1901) in Bandar-e Kiashahr in Southwestern of Caspian Sea during a yearly cycle (between two spawning period) from October 2007 to May 2008. No abnormalities or pathological changes in the ovarian or body of the investigated fish were detected. The aims of this study were confirm to timing, frequency and duration of the spawning period, monitor changes in the gonado-somatic index(GSI), relate (GSI) to the histological characteristics of the ovaries and describe the stages of Kutum oocyte and ovarian development.
64 kutum specimens caught and after separation to assess biological parameters such as length, body weight, gonad weight and sexual maturity stages, were measured and recorded. Gonad samples were taken monthly from the females stained with H&E stain and Samples were studied by light microscope. Different stages of oocyte development (nucleus changes, oocyte diameter and forming of yolk vesicle, yolk granules and lipid droplets) were surveyed.
Findings: Gradual trend of Gonadosomatic index in kutum during biopsy showed that Gonadosomatic index (GSI) began to gradual increase in March and reached the highest value (29.47±4.2) significantly in April and then suddenly drop in early may.
Discussion and According to the results gonad development of Kutum was synchronous group. Four maturity stages were observed during our study that included: Maturing virgin (II), Developing (III), Gravid (IV) and Spawning (V).