EFFICACY OF COMMON CARP Cyprinus carpio TESTIS ENDUCING SEX REVERSAL OF NILE TILAPIA Oreochromis niloticus

Rahul Ranjan, Narayan P. Pandit*, Nabin B. Khanal, Madhav K. Shrestha,
 and James S. Diana
 
 Department of Aquaculture and Fisheries
 Agriculture and Forestry University, Rampur, Chitwan, Nepal
 panditnp@gmail.com

Sex reversal of Nile tilapia (Oreochromis niloticus) using 17α-methyl testosterone is the most commonly used method. An experiment was carried out to explore the possibility of using common carp (Cyprinus carpio) testis as natural androgen source as an alternative for sex reversal of Nile tilapia fry. Six diets containing different proportions of dried common carp testis (CCT) were fed to sexually undifferentiated fry in aquaria for 25, 30 and 35 days. Feed types included 0% (Control), 50%, 65%, 80%, 95% and 100% dried CCT mixed with fish meal. After treatment, fish were transferred to nylon hapas suspended in an outdoor concrete tank and fed with normal diet until they reached 160 days of age.

Feeding CCT to Nile tilapia fry during the critical period of sex differentiation increased the fraction of male fish in a dose-dependent manner (Table 1). The highest proportion of males was 95.8±4.2% grown on the diet of 100% CCT for 30-35 days and lowest proportion was 62.5±7.2% on the diet with 50% CCT fed for 25-30 days. There were significant differences in male proportion with different diets but the differences in male proportion over different times of exposure were not significant. This experiment clearly demonstrates that common carp testis can efficiently masculinize Nile tilapia fry when fed for at least 30 days after hatching. However, it suggests a need for further study on 100% CCT feed and duration of feeding.