Mercury in Marine Fish and Health Advisories

Mercury is a heavy metal that occurs naturally throughout the environment. Unlike other metals, it is a liquid at normal temperatures and is easily transformed into a gas. Many natural processes, such as volcanic activity, and human activities, such as incineration and industrial manufacturing, result in worldwide distribution of mercury.

In large enough doses, mercury is toxic to mammals, birds, and fish. Mercury can cause severe nerve and brain damage, sight and hearing loss, and birth defects. Levels that cause serious illness have only occurred in rare situations of gross pollution or accidental poisonings.
Among the dietary routes for low-level human exposure to mercury, consumption of fish is the most common. The complex relationships between mercury, the atmosphere and marine organisms indicate that mercury contamination of certain marine fish probably predates human uses. Even if all human-related sources were removed, the problem would continue to exist for several generations.

Florida’s marine fish are generally considered safe to eat.  However, certain fish can be potentially unhealthy to eat because those fish can take up contaminants from the water they live in and from the food they eat.  Fish may contain different levels of contaminants based on their location, size, age, length of life, and feeding habits. Although pesticides, algal toxins, and other manmade compounds are of interest to health officials, mercury is currently the contaminant of greatest concern in Florida’s fish. The Food and Drug Administration (FDA) monitors commercial seafood for mercury. In 2004, the FDA and the Environmental Protection Agency (EPA) has recommended that women might wish to modify the amount and type of fish they consume if they are planning to become pregnant, are pregnant, nursing, or feeding a young child. They suggest that these women should not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury. The EPA and FDA has determined that five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish. Another commonly eaten fish, albacore ("white") tuna has more mercury than canned light tuna.

Since 1989, the Florida Fish and Wildlife Conservation Commission (FWC), the Florida Department of Environmental Protection (DEP), and the Florida Department of Health (DOH) have been actively investigating the occurrence of mercury in Florida’s marine environments.  This multi-agency effort has focused on surveying important marine and freshwater bodies and species of fish throughout the state. The State of Florida has collected data on mercury levels in several species of marine fish from around Florida. Accurate species identification and location information is critical. The majority of collections have been made by the Fish and Wildlife Research Institute during regular surveys and fishing tournaments.

Fish consumption advisories for specific water bodies are issued when contaminants found in fish are at levels that may pose a risk to human health.  DOH, in cooperation with DEP and FWC, issues fish consumption advisories.  FWC biologists collect species of concern; DEP scientists analyze fish tissue for mercury, and DOH officials conduct risk assessments and issue fish consumption advisories.  Advisories for mercury in Florida waters have been issued since 1989. The advisories are not intended to discourage anglers from eating fish but should be used to choose fish lower in mercury while limiting consumption of some species of fish from certain waters.

Many Florida waters have been tested for mercury levels in fish.  For these, the DOH Web site offers regularly updated consumption advisories containing specific advice about eating fish from Florida’s fresh and marine waters. Visit the DOH online at the link below to view the advisories. The DOH can also be contacted through regular mail or by telephone:

Florida Department of Health
Bureau of Community Environmental Health
4052 Bald Cypress Way Bin# A08
Tallahassee, FL, 32399-1712
(850) 245-4299

Consumption advice about commercially caught fish sold in supermarkets and restaurants can be found at the Food and Drug Administration (FDA) website and the Environmental Protection Agency (EPA) website via the links below.

Certain species have high contaminant levels and should be avoided, while authorities advise limited consumption of other species. Mercury testing of fish from marine and estuarine waters of Florida has included over 100 species, representing all major groups from primary consumers to apex predators.  Apex predators are fish at the top of the food chain.  These species include many popular sportfish collected from state waters.  The majority of marine and estuarine fishes examined contained low levels of mercury, but levels in individual fish varied greatly within and among species.  Examples of species with low levels include striped mullet, Florida pompano, sheepshead, common dolphin, gray snapper, gulf flounder, and southern flounder.  Many other species also contain low mercury levels.  The current fish consumption advisory provides specific advice regarding Florida marine fishes.