Annual Rhythm of Gonad Development Trend and Ovarian Stages in Caspian Sea Kutum (Rutilus frisii kutum)

The changes occurring in the gonad were studied during cortical alveoli, vitellogenesis and oocyte maturation in of female Kutum, (Rutilus frisii kutum) during March 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 to confirm annual rhythm of gonad development trend, the timing, frequency and duration of spawning period, monitor changes in the gonado-somatic index (GSI). GSI can be relate with the histological characteristics of the ovaries and describe the stages of Kutum oocyte and ovarian development. Gonadal samples were taken monthly from the females stained with H and E stain and 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 during study. This study showed that gonadosomatic index (GSI) began to increase in March and reached the highest value (29.47±4.2) in April and then decreased sharply in early May. According to these results, ovarian development strategy in the Rutilus frisii kutum is synchronous and Spawning occurred once a year during February to April.

Annual Rhythm ; Gonad ; Rutilus frisii kutum ; Caspian Sea