Methylmercury concentration in shark muscle by species, size and distribution of sharks in Florida coastal waters

The concentrations of methylmercury (MeHg) in 124 samples of muscle taken from nine species of common sharks of varying sizes and locations along the Florida coast were determined. Muscle MeHg levels averaged 0.88 mu g/g (wet sample basis) and ranged from 0.06 to 2.87 mu g/g, with 33.1% of the samples exceeding the U.S. Food and Drug Administration's 1 mu g/g action level. Differences were found in MeHg concentration by species but not by sex. A positive correlation between MeHg levels and shark size was found such that most sharks larger than approximately 200 cm total length contained MeHg concentrations exceeding the 1 mu g/g action level. Fetal sharks contained consistently lower MeHg levels than their mothers. Sharks collected off southern regions of the state contained significantly higher MeHg concentrations than those off the northeast coast. The human health concerns for consumers of Florida shark meat are discussed in relation to these findings.