A test by the U.S. Food and Drug Administration revealed that the tuna species with the highest level of mercury is fresh or frozen bigeye, and canned light tuna has the lowest.

The larger the tuna, the more mercury they have. Bigeye tuna develop more slowly and grow to be around 5 ½ feet long, which leads to more mercury in their bodies.

Interestingly, the FDA doesn't include bluefin tuna anywhere in its ranking of mercury content in commercial fish, even though it’s the largest tuna species at over 13 feet long.

However, a 2010 American Museum of Natural History and Rutgers University study found bluefin tuna contains higher amounts of mercury than smaller species like yellowfin.

Canned light tuna most often uses skipjack tuna, which is the smallest tuna species, averaging at 3 feet long. It's very unlikely you'll get mercury poisoning from canned tuna.

Canned albacore has around three times the amount of mercury found in canned skipjack and other light tuna on average. However, most can safely eat it in moderation.