Effects of density on food utilization and surfacing behaviour in the obligatory air-breathing fish Channa striatus

Abstract

Rearing Channa striatus in groups of 1, 2, 4, 8 or 16 individuals/aquarium, effects of density on food utilization and surfacing behaviour were studied. Individuals in the control group consumed more but converted less efficiently. Those reared in higher densities too consumed less and converted far less efficiently, spending greater amount of energy on surfacing. At the optimum density of 4 individuals/aquarium, the fish consumed the highest ration and converted it with maximum efficiency, conserving energy by decreased surfacing activity. Growth of smaller individuals is inhibited in the presence of larger ones at all the tested densities. The inhibition is minimum at the optimum density and is maximum at the densities of 2 and 16 individuals/aquarium. Individuals reared in the maximum density produced maximum but the mean body weight of a single individual was only half of that in the optimum density. The optimum density, which yields maximum production without sacrificing mean body weight, is profitable for aquaculture.