All fish have some mercury in them, though those with the longest lifespan or that eat other fish typically have more. Government agencies monitor mercury levels in fish. Consuming too much mercury can be unhealthy to young children and pregnant women. Consequently, it is important to make sure the fish you eat is safe, as mercury is present in many freshwater and saltwater varieties.
Atlantic salmon have a complex life cycle when compared to other fish, as they can live in freshwater and saltwater habitats. However, they typically contain a low level of mercury. Juvenile Atlantic salmon spend about three years in rivers before making their way to the ocean. The three main groups of this variety are Baltic, European and North American.
Atlantic mackerel are found in the Baltic, Mediterranean and Black Seas, as well as along the Eastern coasts of Canada and the United States. Atlantic mackerel migrate extensively to and from spawning and summering grounds and live in large groups. The Atlantic mackerel is a safe fish to consume because of its low level of mercury.
Pacific flounder and sole
Pacific flounder and sole are both flat fish characterised by having two eyes on the same side of the head. They live primarily on the ocean floor and contain little mercury, which makes them safe for human consumption. These should not be confused with Atlantic flounder and sole, which have higher mercury levels than the Pacific varieties.
Sardines, anchovies and herring
Sardines, anchovies and herring are all frequently canned, smoked or preserved. Because these fish are eaten when they are relatively small, they do not spend a lot of time in the ocean. As a result, they are not exposed to contaminants for long periods of time.
Many types of shellfish, including shrimp, scallops, oysters and crab, are considered safe to eat because they contain a low level of mercury. Northern lobster, however, contains more mercury than other types of shellfish and should be eaten in moderation.