Mercury concentrations in Patagonian toothfish, Dissostichus eleginoides Smitt 1898, among three distinct ocean basins

Patagonian toothfish, Dissostichus eleginoides, collections (n-186) from three ocean basins were analysed for Hg concentration and comparisons were made by gender, total length (TL), wet weight (WW), and basin. There was no difference between TL-WW relationships by gender within any basin across the range examined. However, fish were significantly smaller within the Atlantic basin (mean=84.52 cm; 5.57 kg; n=142) than the Pacific (99.07 cm; 9.12 kg; n=15) and Indian (102.72 cm; 14.0 kg; n=29) basins, which were not different from each other. Similarly, Hg concentration did not differ by gender or size across the range examined and was less for Atlantic basin fish ) mean=0.23 ppm) than either Pacific (0.73 ppm) or Indian basin (0.80 ppm) fish, which did not differ.
The Pacific and Indian basin fish had Hg concentrations within the range found for other fish like shark, swordfish, tilefish, and king mackerel, that are considered high in Hg concentration by the U.S. Food and Drug Administration. In contrast, those from the Atlantic basin were found to have similar lower values in fish like haddock, halibut, cod, albacore tuna, and orange roughy.
Explanation of these geographical differences in Hg may be 1) the noted size differences among basins, or 2) the actual sample locations and associated hydrogeographical and oceanographical conditions. For example, sampling sites for the Pacific Ocean lie well outside the Antarctic Convergence whereas the Indian Ocean sites straddle the Convergence. The Atlantic sites lie well within the Antarctic Convergence, suggesting that the Polar Front may provide some type of hydrographic barrier, as suggested in other studies on Patagonian toothfish, to anthropogenic sources of contamination. With a steady global market demand for Dissostichus this could pose a human health risk that has yet to be adequately explored.