Histomorphological and Biochemical (Serum 17β-estradiol) Characterization of the Reproductive Cycle of Female Common Carp (Cyprinus carpio) in Northeast Italy

To clarify the spawning seasonal dynamics of common carp (Cyprinus carpio) in northeast Italy, female fish were collected monthly from July 2002 to June 2003. The gonadosomatic index (GSI), histomorphology, 17β-estradiol serum concentration, and relative fecundity were compared. Between March-April and May-June, statistically significant differences were found in GSI, 17β-estradiol , and relative fecundity. Intermediate multispawner stages were found by histological analysis of specimens caught in July-August 2002 and May-June 2003. Final maturation stage was found mostly in March-April. Development trends were well correlated with water temperature. Histomorphological analysis revealed that oocytes at the exogenous vitellogenesis stage were retained throughout the winter and final maturation was reached during a short period (March-April). The beginning of the spawning season was fixed between April and May, and the end of the spawning occurred during July and August.