Gulf-Wide Fish Monitoring Program
Dr. Spencer Garrett
National Marine Fisheries Service

Synoptic Survey of Total Mercury in Recreational Finfish in the Gulf of Mexico
E. Spencer Garrett and Tony Lowery
National Marine Fisheries Service

The public health ramifications of mercury (Hg) in fish is a complex issue of numerous dimensions. There are professional differences of opinion on what the allowable tolerance (guideline) in fishery products should be. Methylmercury is an ecotoxicant that bio-accumulates in marine seafood species. There are natural sources and anthropogenic sources of mercury released into the marine environment that through bacterial processes becomes the bio-accumulating ecotoxic Methylmercury. Methylmercury binds to proteins in living organisms and is passed up the food chain where the Methylmercury can reach dangerous levels in certain seafood species.

The strategy to protect the public against ingesting unsafe amounts of Methylmercury has been premised on the following:

1. the average consumer eats approximately 15 pounds of seafood per year;
2. the primary source of seafood for the average consumer is from commercial harvested species; and
3. the amount of seafood consumed can be used to back calculate an acceptable level of methylmercury ingestion,
4. therefore, seafood below 1.0 part per million (ppm) Methylmercury is generally acceptable.

Various consumption advisories have been issued by FDA and EPA encouraging the public, especially women of child bearing age and children to consume seafood species that are low in Methylmercury, and to avoid eating Swordfish, Shark, Tile Fish, and King Mackerel. As Methylmercury can adversely affect the neurological development of fetuses and small children at low doses, women of child bearing age and children are of particular concern. EPA and FDA recognize and have so indicated in 1996, that "...FDA's action levels ensure a safe food supply for consumers of commercial fish, they may not be appropriate levels for ensuring the safety of those who consume locally caught fish...." and therefore various fish consumption advisories have been issued by states to take into account local conditions and local consumption patterns.

There may be an unrecognized portion of the public that consumes seafood in excess of 15 pounds per year, and they also consume large quantities of seafood that are harvested for personal consumption. In particular, subsistence, commercial, and marine recreational fishermen and their families may be at increased risk of exceeding the FDA Methylmercury consumption guidelines as they may be consuming seafood well in excess of 15 pounds per year, and they may be consuming non-commercially harvested seafood that exceeds the FDA's 1.0 ppm
Methylmercury monitoring and restrictions. Therefore, subsistence, commercial, and marine recreational fishermen and their families represent a new sub-population of the seafood consuming public that could likely require additional informational safeguards in order to protect them against excessive Methylmercury ingestion via seafood.

The Methylmercury levels in commonly available commercially harvested seafood species are fairly well known. However, the Methylmercury levels in seafood species not commonly available through commercial sources are less well known. Since the development of consumption advisories for the subsistence, commercial, and marine recreational fishermen and their families should be based on sound science, data on the mercury levels in the seafood species this sub-populations consumes will be collected. NMFS' National Seafood Inspection Laboratory and EPA's Gulf of Mexico Program plan to carry out a synoptic survey analyzing 2,500 samples in 2002-2003 to collect preliminary data on the mercury level for selected popular marine recreational seafood finfish, and to provide data for later more extensive Gulf-wide mercury in seafood survey designs if needed.

The synoptic survey will be carried out in three parts:

1. Estuarine Sampling and Modeling: Selected estuarine finfish will be collected from estuaries with varying degrees of mercury contamination. Previously collected mercury data in oysters from these estuaries will be modeled against the finfishes mercury levels. If the modeling finds that the low oyster's mercury levels can be used as a surrogate for the finfishes mercury levels, then the 31 estuaries of the Gulf Coast could be modeled for their finfishes mercury levels using NOAA's Mussel Watch's previously collected oyster mercury data for the 31 Gulf estuaries.
2. Reef and Rig Sampling: Selected reef finfishes will be collected from oil and gas drilling rigs and non-oil and gas drilling rig reefs. The samples will be tested to determine if a statistical difference exists in the mercury level in the reef finfish caught near the drilling rigs versus those caught near the non-rig reefs. If no difference is observed, then a generic Gulf-wide modeling of the mercury levels in reef fish could be possible. Conversely, if the mercury levels in the reef finfish taken from the vicinity of the rigs are statistically higher than those taken at non-rig reefs, then additional surveys will be required.

Migratory Species Sampling: Selected highly migratory finfish species will be collected from off the Florida Gulf and Texas Coasts. The samples will be tested to determine if a statistical difference exists between the fishes taken from these geographic regions of the Gulf. If no difference can be determined, then a generic Gulf-wide modeling of the mercury levels in these species could be possible. Conversely, if a difference is observed, then additional surveys would be required.

NMFS anticipates that the synoptic survey will, at a minimum, provide valuable data that will allow for an assessment of the scope of sampling required to adequately cover the marine recreational finfishes of the Gulf of Mexico. Such data is needed to support the development of consumption advisories for the general public, and especially for the subsistence, commercial, and marine recreational fishermen sub-population that is believed to be at the highest risk presently.

It should be understood that this NMFS Synoptic Survey deals, in a limited manner, with only one-half of the information needs that address the exposure component of a mercury risk assessment. The other necessary component of the exposure risk assessment is the need for consumption studies for the recreational fisheries and/or commercial fishers (who consume portions of their catch) relative to the species that may be identified as containing elevated mercury levels.

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