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

Abstract

The production characteristics of diploid and triploid sibling African catfish, Clarias gariepinus (Burchell 1822), were compared. Triploid fish were obtained by cold-shocking (5°C) eggs for 40 min starting 3 min after fertilization. The cold-treated group proved to be triploid for about 95%. The untreated group consisted of diploid fish only. The experiment started when the fish were 163 days of age and weighed about 150 g. Two series of seven 150-l glass aquaria were used. Each aquarium contained 24 fish with a varying ratio of untreated and cold-treated fish ( 24 0 , 20 4 , 16 8 , 12 12 , 8 16 , 4 20 and 0 24 respectively). Fish in one series of seven aquaria were fed at a low level (±8.29 g·kg −0.8·d −1). The others were fed about three times as much. The experiment lasted 8 weeks. Growth rate was not significantly ( P>0.05) affected by feeding level nor by percentage of triploids per aquarium. Feed conversion at the high feeding level was significantly ( P<0.01) less efficient than that at the low feeding level. Diploid and triploid fish converted their feed with similar efficiencies ( P>0.05). At both feeding levels less protein, more fat and more energy (all P<0.01) was deposited per gram growth by groups of fish containing more triploids. Male and female diploid fish had significantly higher gonadosomatic indices than triploid fish, irrespective of feeding level. At the high feeding level more ( P<0.01) product remained after gutting triploids than after gutting diploids. It is concluded that decisions in favour of triploid culture should be based on expected advantages concerning body composition and gutted weight.