Tilefish and king mackerel are two such fish, and both were sold to consumers who believed they were procuring red snapper and halibut respectively.

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Larger fish such as shark, king mackerel, swordfish, and tilefish tend to be highest in mercury because they eat smaller fish and consume the mercury in them as well.

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The agency warns, however, that pregnant and breast-feeding women shouldn't eat swordfish, tilefish, shark, or king mackerel and should limit consumption of white, albacore tuna, a commonly canned variety.

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