Long-term data on the induced spawning of common carp (Cyprinus carpio) at a large-scale hatchery were evaluated. Breeders at the farm prefer medium-size fish with body weights between 4 and 8 kg. The number of females selected for propagation in the first period of the spawning season made up about half of the total number of females (47.5%). The average spawning ratio from the data of 2620 females receiving hormonal injections was 79.8%. From the egg production data of 2086 females, the average pseudogonadosomatic index (PGSI) was calculated as 16.3 ± 5.87% (mean ± SD) for the same period. There was a high correlation between fish weight and the time of induction, determined by the breeder on the basis of secondary sexual characteristics. The similarity of the responses of females among the different weight categories proved the reliability of this method for identification. The time of induction has a significant effect on both the responsiveness of the females and the relative quantity of eggs released. Spawning ratio was significantly lower in the third period of the reproductive season, compared with those in the first and second period. Mean PGSI for the third period was significantly lower than that for the first period. The considerable decrease of both reproductive parameters by the end of the spawning season is attributed to ovarian atresia. The spawning ratio and the mean PGSI for the mirror and scaled varieties were similar.
ASJC Scopus subject areas
- Animal Science and Zoology