Bioaccumulation of toxic metals in fish cause serious threats to human when consumed. The detection of toxic element concentration in fish is important and mercury especially in the form methyl mercury is very toxic to fishes. Prolonged consumption of fishes containing mercury (especially methyl mercury) can damage the liver and brain of human. It could cause birth defects in pregnant women. The objective of this study was to assess the mercury level in fish muscle and liver of the Gulf of Mannar coast, Tamil Nadu. The fish samples were collected fortnightly from different stations namely Kayalpatinam (Staion - I), Kombuthurai (Station - II), and Thoothukudi thermal bridge (Station - III) for a period of eight months. The fish species analyzed for the presence of mercury were Honey comb grouper (Epinephelus meera), Checkered snapper (Lutjanus decussates), White spotted spine foot (Siganus canaliculatus), Black tail snapper (Lutjanus fulvus), Blue lined hind (Epinephelus formosa), Short silver belly (Parupeneus indicus), Ornate emperor (Lethrinus ornatus), Streaked spine foot (Siganus javus), Blue barred parrot fish (Scarus ghobban), Pink ear emperor (Lethrinus lentjan) in all the stations throughout the study period. The fish were placed in sterile polythene bags in ice box and bought to the laboratory on the same day. Each fish was properly rinsed with distilled water to remove debris, plankton and other external adherents. Scales were removed and liver and muscle were separated and then transferred into sterile sample bottles and kept for digestion. The mercury analysis was done using Inductive Coupled Plasma-Mass Spectrometer (ICP-MS) technique at SGS laboratory Pvt. Ltd, Chennai. The result showed that mercury levels in muscle and liver tissues of all fish samples in three different stations (Kayalpatinam - Station I, Kombuthurai - station II and Thermal Bridge - Station III) were below the limit of quantification (BLQ) of 0.01mg/kg throughout the study period.
The mercury level in all the fish samples were found below the quantification limit of 0.01mg/kg as recommended by WHO (1985) (0.1 mg/kg); FDA (1996) (0.1 -0.5 mg/kg); NHMRC (1990); (1mg/kg) and EC (2000) (1.0 mg/kg) standards. This might be due to the efficient effluent treatment measures and good management practices followed in the industries in and around Thoothukudi coastal waters in recent years.