An Assessment of Mercury in Economically Important Fishes Commonly Landed off the Coast of North Carolina

Marine fish are an important dietary component for wildlife and humans, particularly because they contain high quality protein and essential nutrients, are low in saturated fats, and tend to be good sources of omega-3 fatty acids.  However, fish (marine fish in particular) are also the primary source of human and wildlife exposure to mercury, a potential neurotoxin that presents significant risk to pregnant women and children.  Though fish harvest and consumption is an important part of North Carolina’s heritage and economy, little is known about the Hg concentrations in marine fish commonly caught and consumed by our residents.  The goal of this study was to examine mercury levels in six commonly caught and consumed marine species in North Carolina, comparing our results to published fish consumption guidelines.  Specifically, we (1) quantified and compared tissue Hg levels of dolphinfish, Coryphaena hippurus; king mackerel, Scomberomorus cavalla; and wahoo, Acanthocyblum solandri caught recreationally, and porgy, Pagrus pagrus; red grouper, Epinephelus morio; and triggerfish Balistes capriscus, caught commercially and sold to local seafood markets, and (2) compared tissue Hg levels of these species with mercury consumption recommendations established by the Environmental Protection Agency (EPA), Food and Drug Administration (FDA), and the Monterey Bay Seafood Watch list.  Tissue samples were collected over a three month period when each species was in season.  Preliminary results indicate significant differences in Hg content among the targeted species.  In particular, dolphinfish had significantly less Hg (0.07 ppm mean) than other targeted species.  Though higher than dolphinfish, the mercury content of porgy was also relatively low (0.19 ppm mean), and nearly all (93%) individuals of both species were below EPA’s Hg action level (0.3 ppm), the most conservative of those that we examined.  Conversely, nearly all collected wahoo (0.46 ppm mean) and red grouper (0.56 ppm mean) exceeded the EPA Hg action level, and 10% of wahoo had mercury concentrations high enough to exceed the FDA action level (1.0 ppm). In general, we found a positive relationship between fish length and tissue Hg concentration.  Ongoing research will examine Hg trends for triggerfish and king mackerel, though preliminary data suggest that king mackerel will have very high levels of Hg contamination.  Thus far, our results suggest that dolphinfish and porgy are good choices for NC consumers and that consumption of wahoo and grouper should be limited or avoided, particularly by those in a high risk segment of the population.