Abstract:
Consumption of fish contaminated with non essential heavy metals such as Pb, Hg and Cd metals which exceed the required limits pose a risk to human health. Bioaccumulations of heavy metals in fish depend on several factors such as increased levels of industrial pollution and domestic solid waste dumping in the estuary. Based on the pollution inputs into the estuary, it is considered that different localities within the estuary are polluted at different rates. The objectives of this study were to determine the non essential heavy metals concentration in fish tissues and assess the seasonal variations in the ecosystem. For this study, fish tissue samples were collected from nine sampling locations along the North (n =3), South (n=2), West (n=2), and East (n=2) parts of the estuary for a period of one year from January to December 2014. Fish tissue heavy metals levels were analyzed employing standard methods. Results revealed that the average concentrations (mg/kg) varied from Pb 0 to 0.15 ± 0.06, Cd 0.35 ± 0.16 to 1.04 ± 0.28 and Hg 0.0005 ± 0.0004 to 0.05 ± 0.046 mg/kg respectively. The detected levels were below the maximum permissible limits for hazardous substances in fish and fishery products for recommendation of FAO. The detected lead, mercury and cadmium contents in fish tissue were below the standard limits defined for each element < 0.5 mg/kg < 0.05 mg/kg and < 0.05 mg/kg respectively. Significant differences (P< 0.05) were observed for Pb and Hg depending on fish tissues. The levels of Pb and Hg metals in muscle tissue were lower than the standard limit for FAO. The value obtained on Cd 1.04 ± 0.28 mg/kg concentration was much higher than the permissible threshold limit observed in the north, south, east and west regions. The most prominent increases in Pb and Cd metal concentrations in fish tissue were found during the October, November and December study of 2014, which corresponded to peak periods from October, November and December which apparently coincided with the second inter monsoon of the island respectively.
