Heavy metal bioaccumulation in commercial Lethrinidae fish species in Mauritius

Concentrations of heavy metals arsenic, cadmium, lead and mercury and trace elements chromium, copper, nickel and zinc were tested in the muscle tissue of four commercial edible lethrinids fish species from different region of Mauritius. Sky emperor (Lethrinus mahsena) was collected from coastal regions as well as offshore regions (banks) for this study. Blackspot emperor (Lethrinus harak) and spangled emperor (Lethrinus nebulosus) were also studied for their popularity in the fish market. Condition factor was calculated for each fish and the highest value obtained was in Lethrinus mahsena collected from offshore regions (2.598 cm/g). Flame atomic absorption spectrometry was used to analyse copper, nickel and zinc while, graphite furnace technique was used for cadmium, chromium and lead. Mercury levels were evaluated with the cold vapour technique and arsenic with the thermal hydride cell. The level of lead, mercury, copper, nickel and zinc ranged from 0.0011-0.0024 mg/L, 0.0016-0.0036 mg/L, 0.080-0.389 mg/L, 0.566-1.192 mg/L and 0.219-0.422 respectively in wet weight. Interspecies variations in levels of heavy metals and trace elements were observed for nickel and no significant variations occurred for mercury, lead and zinc. Concentrations of heavy metals and trace elements were all within the permissible level except for nickel. As per this study, the Food Act 1998 of Mauritius must be reviewed in order to incorporate the Maximum Permissible Level for nickel.