The development of carp gonads in warm water aquaria

Abstract

The development of carp gonads in warm water (23°C) aquaria under controlled conditions is described. In this environment males mature at 6 months of age. Females ripen at 14 months, and by 15 months 25% of these have started to spawn, whereas under natural conditions female European carp do not ripen until they are 4 years old. Fishes do not lay all their eggs at once, as evinced by the finding of partly‐spent ovaries. Sexual maturation of the ovaries has been described in six stages, based on histological changes, and associated with changes in the female gonado‐somatic index and the maximum ova diameter. The maturation of testes occurs in four stages. The percentage incidence of each stage of ovarian maturation has been calculated for the 6th to the 15th month. Larger fishes become sexually mature before smaller fishes.