Sublethal effects of carbaryl on surfacing behaviour and food utilization in the air-breathing fish, Macropodus cupanus.

Sublethal effects of carbaryl on surfacing behaviour and food utilization in the obligatory air-breathing fish Macropodus cupanus were studied by rearing the fish individually in freshwater (pesticide-free) and four different sublethal concentrations of carbaryl (1 to 2.5 ppm). M. cupanus exhibited increased surfacing with the increased concentration of carbaryl. Enhanced rate of surfacing may be the result of stress exerted by the toxicant. Food intake of M. cupanus reared in different concentrations of carbaryl did not vary significantly. Growth decreased with increased concentrations of carbaryl, possibly due to excessive expenditure of energy on metabolism that otherwise could have been channelled into fish growth. Frequent surfacing may also account for the expenditure on metabolism. Hence, the conversion efficiency of M. cupanus reared at higher concentrations of carbaryl was poor and was inversely related with higher concentrations of carbaryl.