Abstract

Total mercury (Hg) concentrations were determined in the tissues of 11 species of pelagic fishes, with a special emphasis on apex predators (large vertebrates). Highest mercury concentrations were observed in blue marlin (Makaira nigricans), Carcharhinid sharks (genus Carcharhinus)and little tunny (Euthynnus alletteratus), ranging from 1.0 to 10.6 ppm. Moderate to low concentration (< 1.0 ppm) were observed in greater amberjack (Seriola dumerili), blackfin tuna (Thunnus atlanticus), cobia (Rachycentron canadum), king mackerel (Scomberomorus cavalla), little tunny (Euthynnus alletteratus), wahoo (Acanthocybium solandri), yellowfin tuna (Thunnus albacares) and dolphinfish (Coryphaen hippurus). For the majority of species examined, contaminant loads of mercury did not vary significantly between two consecutive years (2002 and 2003) and between two adjacent locations (Texas and Louisiana). The relationship between Hg concentration and fish size was also explored in certain species. Several species showed a positive relationship between mercury level and body size. Natural dietary tracer, stable isotopes of nitrogen also showed that Hg levels in fish tissues were positively associated with trophic position. Our findings in this study not only added to the information on mercury contamination in pelagic fish, but also furthered our understanding on mercury accumulation in these fish.

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