Effect of Body Size on Metal Concentrations in Wild Puntius chola

Abstract

In this study, relationships of body size (length and weight) with metals i.e., zinc, iron, copper, manganese and calcium in freshwater wild Puntius chola (whole fish) have been derived. Metal concentration levels in dried fish powders have been determined by flame atomic absorption spectrometry following wet digestion method involving the use of HNO3 and H2O2. Mean concentrations (g g-1 dry weight) of the metal in carcasses of wild Puntius chola have been found to be as 170.8 (Zn), 538 (Fe), 21.2 (Cu), 8.8 (Mn), and 69.10 (Ca, mg g-1 dry weight). Cadmium concentration was below the limit of detection of the technique. It was observed that all metals except copper showed significant positive correlation (p < 0.001) with total body weight or total body length. All metals, except cadmium which was not quantifiable, were found to increase in direct proportion to an increase in body weight showing isometry (when the value of slope b is either equal to 1.0 or not significantly different from 1.0). Calcium was found to increase in direct proportion to an increase in total length indicating isometric relationships (when the value of slope b is either equal to 3.0 or not significantly different from 3.0). Manganese showed positive allometry i.e., significant proportional increase in metal concentration with increase in body length which suggests that the metal is probably accumulated at higher rate compared to its rate of excretion as the fish grows. However, zinc, iron and copper showed negative allometry to an increase in total length, i.e., significant proportional decrease in metal concentration with increase in body length which suggests that these metals are probably accumulated at lesser rate compared to its rate of excretion as the fish grows.