Through a process known as bioaccumulation, mercury becomes more concentrated with each step up the food chain. When smaller species are exposed and then bigger fish eat them, they absorb the mercury contamination of the smaller fish. Since bigger fish eat on a regular basis, they accumulate more mercury in their system than smaller, non-predatory fish do. Young fish also contain less mercury than older ones.
Because of this, mercury can concentrate more in certain species of seafood, making some food choices riskier than others. Unfortunately, the types of fish we eat often have the highest accumulation of mercury. Here are the average mercury levels by types of selected seafood:
Very low mercury levels
- Shrimp
- Salmon
Below average mercury levels
- Crabs
- Catfish
Above average mercury levels
- Cod
- Canned light tuna
Moderately high mercury levels
- Halibut
- American lobster
High mercury content
- Grouper
- Canned/Albacore tuna
Very high mercury content
- Swordfish –
- Tuna sushi/Bluefin Tuna
Other seafood high in mercury that your family should avoid:
- King mackerel
- Atlantic salmon
- Chilean seabass
- Shark
- Unidentified or farmed shrimp
- Tilefish
- Canned white tuna
- Fish caught in local lakes and rivers (unless you’ve checked the fish advisories first)
Fish and seafood that is low in mercury
Here are some healthy, eco-friendly seafood options that are low in mercury:
- Farmed abalone
- Farmed catfish
- Farmed caviar
- Farmed clams
- Blue crab
- Dungeness crab
- Snow crab
- Stone crab
- Flounder
- Northern shrimp
- Oregon shrimp
- Spot praws
- Farmed strip bass
- Haddock
- Atlantic herring and anchovies
- Atlantic mackeral (NOT king mackerel)
- Mahi mahi
- Farmed mussels
- Farmed oysters
- Wild Alaskan or Pacific salmon
- Canned wild pink or sockeye salmon
- Sardines
- Bay scallops
- Farmed scallops
- Farmed sturgeon
- Farmed trout