With the exception of occupational exposure, fish are acknowledged to be the single largest source of mercury for the human beings. Nevertheless, there are stringent quality guidelines imposed by the statutory authorities for mercury in seafood under fish export regulations to ensure food safety. Hence, the present study was undertaken to determine the total mercury contents in four major exported food fish species of high economic importance to Sri Lanka to see whether the levels exceed the legal limits. Total mercury concentrations were measured from the muscle tissue of Xiphias gladius (n=50) , Carcharhinus limbatus (n=45) , Makira indica (n=40) and Thunnus albacares (n=50) by colorimetric dithizone method using standard analytical procedures during the period from January to December, 2002.
The highest level of total mercury was found in Xiphias sp . where the values ranged from 0.03 – 0.47 mg/kg wet wt with a mean value of 0.22 mg/kg wet wt. The second largest mean value for the total mercury (0.13 mg/kg wet wt) was recorded from the Carchairinus sp and the levels ranged from 0.06-0.45 mg/kg wet wt. The mean values of total mercury (0.05 and 0.04 mg/kg wet wt) in Thunnus sp and Makira sp were significantly lower (p<0.05) than those in the Xiphias sp . According to the rules in force, none of the samples exceeded the peak value of 1 mg/kg wet wt declared by the European Commission and the Food and Drug Administration, USA for human consumption. Correlations between the specimen weight and the mercury content were evident in all four species examined.
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