Differences in growth rate and feed utilization between male and female African catfish, Clarias gariepinus (Burchell 1822)

Abstract

Performances of all-male, all-female and mixed-sex (1:1) groups of African catfish, Clarias gariepinus (Burchell 1822), were compared at 25°C in two separate experiments, using weight ranges from 70 to 200 g (Experiment 1) and from 200 to 400 g (Experiment 2). Three feeding levels were applied in each experiment, using a commercial trout diet. Growth rate and feed conversion were significantly affected by feeding level in both experiments. All-male groups had a higher growth rate and better feed conversion than all-female groups, especially in the weight range from 200 to 400 g. Both males and females of mixed-sex groups at the intermediate feeding level, which is also the level recommended for commercial production, had higher growth rates than fish of the respective mono-sex groups. The gonadosomatic index was significantly affected by feeding level and sex composition of groups. Fish at the lowest feeding level had a higher gonadosomatic index than fish fed at higher levels. The mean gonadosomatic index of mixed-sex groups was higher than the average over all-male and all-female groups together, due to an increased index for females from mixed-sex groups. Yield after gutting was significantly affected by sex composition of groups, but not by feeding level. Gutting of males gave the highest yield. The results of the present experiments show that male African catfish can attain a higher growth rate and better feed utilization than female fish. Moreover, more product will remain after gutting. Growth rate and feed utilization of mixed-sex groups can be at least as good as those of all-male groups, due to a positive male-female interaction. Decisions in favour of mono-sex male culture should therefore be based on expected advantages in yield after gutting.