In our study, the general trend for GSI in hybrids was to be intermediate between common carp and gibel carp. In spring, the gonads of
common carp and gibel carp were highly different, suggesting some differences in reproduction aspects. Generally, the reproduction times of
both species overlap. However, there are two aspects that could explain
the observed pattern of GSI and the presence of F1 hybrids with a maternal origin in gibel carp. In spring, even though the males of both gibel