According to research, there may be an answer to mercury toxicity....Selenium:
Researchers conclude that dietary selenium reduces the accumulation and enhances the elimination of mercury in fish.The most important factor to consider when eating fish is the relative amount of selenium the fish contains. Visit the ncbi.nlm.nih.gov's site and look for study pubmed/25481787 for detailed scientific insight.
The best way to supplement is with a high-selenium yeast - always choose the organic form to avoid inorganic and potentially bad products.