Effect of sublethal copper on growth efficiency of the shrimp, Metapenaeus dobsoni (Miers)

Energy utilization and growth are regarded as important biological indices to interpret stress effects in the case of aquatic organisms. In this investigation, an attempt is made to elucidate the effect of copper at sublethal concentrations, on the energy conversion and growth efficiency of a commercially important penaeid shrimp Metapenaeus dobsoni. Juvenile M. dobsoni were exposed to 0.05 and 0.15 mg Cu l super(-1). The animals were fed ad libitum on fish meat or clam meat. Animal tissue, faecal pellets and feed were analysed for CHN and the caloric values were calculated employing a stoichoimetric model. Growth rates of animals maintained under controlled conditions and those exposed to 0.05 mg Cu l super(-1) were not significantly different suggesting tolerance of the animal to low concentration of copper in the culture media. The differences between the assimilation rates for different treatments were also not statistically significant even though variations were noticed in the feeding rates of animals exposed to the heavy metal. Animals exposed to the higher concentration of copper (0.15mg Cu l super(-1)) resulted in lesser growth efficiency. The differences in gross and net growth efficiency were statistically significant. It was observed that the energy utilization for maintenance was increased in the case of M. dobsoni exposed to copper. Such enhanced energy expenditure led to reduction in somatic growth.