372 



Mercury levels In four species of sharks from 

 the Atlantic coast of Florida 



Douglas H. Adams 



Florida Marine Research Institute 



Florida Department of Environmental Protection 



1220 Prospect Ave , Suite 285 



Melbourne, Florida 32901 



E mail address adams_dti gepic7dep state fl us 



Robert H. McMichael Jr. 



Flonda Marine Research Institute 



Florida Department of Environmental Protection 



100 Eighth Ave SE 



St. Petersburg, Florida 33701 



Florida's commercial and recre- 

 ational shark landings represent a 

 significant portion of the total U.S. 

 Atlantic shark landings (NMFS, 

 1993). Shark landings have in- 

 creased significantly during the 

 past decade because human con- 

 sumption of shark meat has become 

 increasingly acceptable and be- 

 cause, in Asian markets, the de- 

 mand for shark fins is very high — 

 as are the prices paid for them 

 (NMFS, 1993; Brown, in press). The 

 east-central coast of Florida is an 

 important area for commercial and 

 recreational shark fishing, and a 

 wide array of shark species, includ- 

 ing those examined in this study, 

 are landed in this region (Trent et 

 al., 1997; FDEP'). 



Mercury, a toxic metallic ele- 

 ment, has been shown to bioac- 

 cumulate in fish tissue, and there- 

 fore, fish can represent a major di- 

 etary source of mercury to humans 

 (Phillips and Buhler, 1978; Turner 

 et al., 1980; Lyle, 1986). Methyl- 

 mercury is the most toxic form of 

 mercury for humans to consume 

 (Meaburn, 1978; NMFS, 1993) and 

 essentially all mercury found in fish 

 muscle tissue (>95'}f ) is in the 

 monomethyl form (CH,3Hg)(Grieb 

 et al., 1990; Bloom, 1992). There- 

 fore, the measurement of total mer- 

 cury provides an approximation of 



methylmercury and has been rec- 

 ommended as the standard for 

 regulatory monitoring (Bloom, 

 1992). Elevated mercury concentra- 

 tions in fish have been a growing 

 concern among resource manage- 

 ment agencies. Apex predators, par- 

 ticularly long-lived species such as 

 billfishes (Forstner and Wittman, 

 1981; Barber and Whahng, 1983; 

 Kai et al., 1987), tunas (Miller et 

 al., 1972), mackerels (Meaburn, 

 1978). and sharks (Forrester et al., 

 1972; Walker. 1976; Lyle, 1986; Vas, 

 1991; Hueter et al., 1995, and oth- 

 ers ) have been reported to accumu- 

 late relatively high levels of mercury. 

 In May 1991, the Florida Depart- 

 ment of Health and Rehabilitative 

 Services (FHRS) released a health 

 advisory urging limited consump- 

 tion of all shark species from 

 Florida waters." Owing to mercury 

 concentrations in excess of U.S. 

 Food and Drug Administration and 

 State of Florida standards, FHRS 

 recommended "adults should eat 

 shark no more than once a week; 

 children and women of childbear- 

 ing age should eat shark no more 

 than once a month." State of Florida 

 guidelines recommended that fish 

 containing less than 0.5 ppm of to- 

 tal mercury should represent no 

 dietary risk, fish containing 0.5 to 

 1.5 ppm of total mercury should be 



consumed in limited amounts, and 

 fish containing greater than 1.5 

 ppm of total mercury should not be 

 consumed. The 1991 health advi- 

 sory regarding sharks in Florida 

 waters was derived from a limited 

 number of samples taken from re- 

 tail sources and from studies that 

 lacked important information re- 

 garding species, capture location, 

 sex, and size of sharks examined. 

 Increased landings of sharks in 

 Florida for human consumption 

 (Brown, in press; FDEPM has 

 prompted the need for more de- 

 tailed information regarding mer- 

 cury levels in Florida shark species. 

 Consequently, we report here 

 analyses of total mercury levels in 

 the muscle tissue of three carcha- 

 rhinids (bull shark, Carcharhinus 

 leiicas; blacktip shark, C. limbatus; 

 and Atlantic sharpnose shark, Rhizo- 

 prionodon terraenovae) and one 

 sphymid (bonnethead shark, Sphyr- 

 na tibiiro ) from the east-central coast 

 of Florida. 



Materials and methods 



Sample collection and mercury 

 analysis 



Sharks were collected during the 

 Florida Department of Environ- 

 mental Protection, Florida Marine 

 Research Institute's Fisheries-In- 

 dependent Monitoring Program in 

 the Indian River Lagoon system 

 and adjacent coastal waters or from 

 commercial gillnet or longline fish- 

 eries operating in the nearshore 



' FDEP I Florida Department of Environ- 

 mental Protection) Marine Fi.sheries In- 

 formation System. Fi.sheries Assessment 

 Section. 100 Eiglith Ave. SE, St. Peters- 

 burg, FL 33701. 



- FHRS (Florida Department of Health and 

 Rehabilitative Services). 1991. Health 

 Advisory for Marine Fish. 1317 Winewood 

 Blvd.. Tallahassee. FL 32399, 3 p. 



Manusci-ipt accepted 20 May 1998. 

 Fish. Bull. 97:372-379 1 19991, 



