Seasonal reproductive dynamics in common carp (Cyprinus carpio): Variations in gonadosomatic index and hormonal profiles

This study investigated the seasonal reproductive cycle and hormonal dynamics in common carp (Cyprinus carpio var. communis), emphasising variations in the gonadosomatic index (GSI) and gonadotropin hormones (GtH-I and GtH-II). GSI remained low from late summer to December and peaked in May, reaching 9.5±0.46 in males and 16.3±0.12 in females. GtH-I levels showed minimal fluctuations throughout the year and had no significant correlation with GSI. In contrast, GtH-II exhibited marked seasonal variations, peaking in May (1.26±0.03 IUl-1 in females and 0.36±0.15 IUl-1 in males), with a strong positive correlation with GSI (females: r = 0.91, males: r = 0.84). These findings highlight the pivotal role of GtH-II in regulating gonadal development and reproductive timing in common carp, providing insights into its endocrine control mechanisms.