Relation between age and heavy metal content in the otoliths of Pomadasys stridens Forskal 1775 collected from the Arabian Gulf

A total of 216 otolith samples (89 male, 127 female) from Pomadasys stridens (Forskal 1775), a common fish of the Arabian Gulf, were analyzed for the concentrations of heavy metals. Standard length, age, sex, body, and otolith weight were recorded for each fish. Otolith weight from male fish was found in the range of 0.047-0.143 g with a mean value 0.101 ± 0.023 g, whereas, mean otolith weight from female fish samples was 0.111 ± 0.019 in the range of 0.062-0.151 g. Average concentration of zinc, copper, manganese, nickel, cadmium and lead was found 0.965, 0.229, 0.195, 0.122, 0.100, and 0.119 μg per otolith in case of male fish and in females it was 1.371, 0.241, 0.297, 0.133, 0.089, and 0.123 μg per otolith, respectively. At the age of two to three years, concentrations of all the analyzed elements, except for Cd, were found higher in otoliths of female fish samples, but at the age of four years this difference becomes minimum and mostly opposite, i.e., otoliths of male fish have little higher concentrations as compared to otoliths from females. The concentration variation of different elements was different in males and in females, but was not statistically significant. The otolith weight at the age two years was significantly different with other age group samples and among both sexes.