Production of all male population of Indian catfish Heteropneustes fossilis (Bloch) by immersion and oral treatment of 17α-methyltestosterone

Abstract

Male dominated population of Indian catfish, Heteropneustes fossilis (Bloch) was produced through immersion and oral treatments with 17a-methyltestosterone (17a-MT). Two approaches were tested in immersion treatment. A group of fertilized eggs was exposed to a short duration treatment of 3 h with 17a-MT at 0, 50, 100, 150 and 200 µgl-1 and another group to a long duration treatment of 10 days at the same doses. A separate group of 3 days old hatchlings were fed with the hormone at 0, 5, 10, 15 and 20 mg kg-1 feed over a period of 28 days. Gonadal histology of the fishes 4 months post-treatment revealed significant (p<0.01) masculinising effect of 17a-MT both in orally and immersion treated groups over the control. Among orally treated groups, most significant (p<0.01) effect was observed in the group that received hormone @5 mg kg-1 feed where 92.27% males were produced as compared to 43.05% males in the control group. Highest rate of masculinisation (97.56%) was achieved in short term immersion in 100 µgl-1 followed by 96.29% in 50 µgl-1, whereas, in long term immersion, it was 92.59% in 50 µgl-1 followed by 92.41% in 100 µg l-1. There was no significant (p>0.05) difference between 50 and 100 µg l-1 concentrations in both short term and long term immersion treatments.