Behavioural and endocrine study of Oreochromis aureus, with special reference to sex-reversed males. In Proceedings of the Fifth International Symposium on the Reproductive Physiology of Fish

The relationship between social status and hormonal profiles (T, E2,11-KT, T3 and 74) was analysed in normal tilapias Oreochromis aureus. Dominant females and dominant males exhibited respectively T and 11-KT plasma level higher than subordinate fish of the same sex.Moreover, the behaviors of females and 17a-ethynylestradiol sex-reversed males (pseudo-females) were studied in mixed pairs or assemblages (4,6 or 8 fish in 500l and 10 fish in 100 l). The results suggested that pseudofemales were more aggressive and dominant that females. Activity rhythms were similar in females and pseudo females.