Total mercury and methyl mercury concentrations in fish from the Persian Gulf and the Caspian Sea

In order to understand the bioaccumulation of mercury in fish in the Iranian coastal waters of the Caspian Sea and the Persian Gulf, different fish species were sampled from both regions in January 2002. Mullet fishes were sampled from the Caspian Sea and six other species from the Persian Gulf: Largetooth flounder, Spotfin flathead, Japanese threadfin bream, Greater lizardfish, Elongate sole and Giant seacatfish. In the Persian Gulf, total Hg concentrations in fish ranged from 0.0123 to 0.0867 mg kg(-1) w.w. (0.0614 to 0.433 mg kg(-1) d.w.). Methylmercury accounts for 64-100% of the total mercury. Highest mercury concentrations were observed in the predatory fish: Giant seacatfish, Threadfin bream and the larger Greater lizardfish caught near Mogham Port. In these species the methylmercury fraction is always higher than 90%. A low methylmercury fraction was only observed in the smallest specimen of flounder and Elongate sole. In the Caspian Sea Hg concentrations in Mullet ranged from 0.0102 to 0.108 mg kg(-1) w.w. The observed concentrations are comparable to those found in other areas of the Persian Gulf as well as in other marine environments and are much lower then the WHO guideline of 0.5 mg kg(-1) w.w.