A mercury chart for fish is available at NDRC.org. The Natural Resources Defense Council hosts a comprehensive list of seafood species that contain the least, moderate, high and highest amounts of mercury.
Species such as anchovies, crabs, salmon and sardineshe have the least amounts of mercury. Species such as cod, halibut, lobster, snapper and canned tuna contain moderate amounts of mercury. Swordfish, mackerel, tilefish and bigeye tuna have the highest amounts..
NDRC.org also lists amounts of various types of fish that may safely be eaten by women who are pregnant. NDRC.org hosts a mercury calculator that allows a user to enter the type and quantity of fish eaten in the past week to determine the average daily mercury dose and compare it with government standards.
Mercury is a neurotoxin that affects the brain and nervous system and is particularly dangerous for women who are pregnant as it can have adverse effects on a child’s development. Mercury does not break down once it enters a waterway and accumulates at increasing levels. Large predatory fish such as swordfish, sharks and tuna may contain mercury levels in their bodies that are 10,000 times higher than their surrounding habitat.