Maturational gonadotropin hormone (GtH) and gonadotropin releasing hormone (GnRH) changes during growth and sexual maturation of female carp (Cyprinus carpio L.)

Fish originating from one couple of spawners were investigated with respect of GtH in the blood and pituitary, GnRH in the hypothalamus and pituitary (RIA), gonadosomatic index (GSI) and histology of gonads, GSI was showing great variability between specimens. The circulatory GtH levels did not fluctuate much troughout the investigated period except at the beginning of vacuolisation of the oocytes when peaks of GtH were observed. GtH in the pituitary started to accumulate from 13 months andGnRH from 33 months. GnRH contents int the hypothalami of the young females before 35 months were also very low, thereafter they increased and showed great variation