Total and organic mercury concentrations in the muscles of Pacific albacore (Thunnus alalunga) and bigeye tuna (Thunnus obesus) Chiee-Young Chen a , Chien-Cheng Lai b , Kuo-Shu Chen c,d , Chien-Chung Hsu d , Chin-Chang Hung c,e , Meng-Hsien Chen c,⇑ a Department of Environmental Engineering, National Kaohsiung Marine University, Kaohsiung 81143, Taiwan b Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung 80424, Taiwan c Department of Oceanography and Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung 80424, Taiwan d Institute of Oceanography, College of Science, National Taiwan University, Taipei 10617, Taiwan e Taiwan Ocean Research Institute, National Applied Research Laboratories, Kaohsiung 85243, Taiwan article info Article history: Available online 18 February 2014 Keywords: Hg pollution Heavy metal Growth dilution Methylmercury Predatory fish Seafood safety abstract Muscles of 115 North Pacific albacore (ALB, Thunnus alalunga) and 75 Pacific bigeye tuna (BET, Thunnus obesus), collected from 2001 to 2006, were analyzed. No ALB, but 13 large BET had organic mercury (OHg) concentrations exceeding 1 lgg À1 wet weight. For both ALB and BET, total mercury (THg) and OHg concentrations were significantly and positively correlated with fork length (FL) and body weight. The muscle Hg bioaccumulation rates of BET were higher than those of ALB, particularly in the adult fish. Moreover, the lines had crossover points among the two species that imply the young BET (FL < 110 cm) contains lower muscle Hg concentrations than ALB of the same size. The suggested weekly dietary intake of ALB and small-BET meats is 340 g, and of BET meat it is 150 g for a 60-kg person based on the provi- sional tolerable weekly intake (PTWI) of methylmercury set by the WHO. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Methylmercury (MeHg), a metal–organic compound, is an envi- ronmental toxicant and is produced by microorganisms through biomethylation of mercury (Hg) in the natural environment (Clarkson et al., 2003). High MeHg exposure (Hg poisoning) in hu- mans can cause adverse health effects, for example, the Minamata disease (Harada et al., 1998). Fish is a key food source of Hg expo- sure in humans (Wheeler, 1996), and MeHg is the major organic compound of Hg in fish (Storelli et al., 2005). Many publications have demonstrated that predator fishes occupying higher trophic levels have higher Hg contaminations because Hg can be biomagni- fied in predator fishes through marine food chains (Bargagli et al., 1998; Storelli et al., 1998, 2007). Studies have also shown that high Hg exposure in humans is associated with the consumption of contaminated predatory fishes (Storelli et al., 2002, 2005, 2007). Therefore, scientists and health administrators worldwide are con- cerned about Hg exposure from consuming large predatory fish. Tunas are migratory predators occupying high trophic positions in marine ecosystems and are important fisheries resources for many nations. Owing to their excellent movement ability, high Hg contamination in tunas is an indicator of non-point global Hg pollution in the ocean. For food safety reasons, Hg contamination in local and imported tuna products has been a concern for many nations (U.S. Food and Drug Administration, 2011; World Health Organization, 2008). Although many publications have reported Hg concentrations in tuna muscle (e.g., Besada et al., 2006; Boush and Thieleke, 1983; Kumar et al., 2004; Menasveta and Siriyong, 1977; Sun and Chang, 1972; Yamashita et al., 2005), relatively few- er studies on total mercury (THg) and organic mercury (OHg) have been reported for North Pacific albacore (ALB) Thunnus alalunga and Pacific bigeye tuna (BET) Thunnus obesus. In particular, inter- specific and intraspecific (gender and size) factors affecting OHg bioaccumulation in the muscles of these two tunas have seldom been studied. For many marine fishes of high trophic levels, including tunas, sharks and swordfish, studies have shown that muscle Hg contam- ination relates to their body size (Besada et al., 2006; Menasveta and Siriyong, 1977; Sun and Chang, 1972; Yamashita et al., 2005). For Pacific ALB and BET, positive correlations between mus- cle Hg concentration and fish size have also been previously re- ported (Boush and Thieleke, 1983; Morrissey and Geise, 2006; http://dx.doi.org/10.1016/j.marpolbul.2014.01.039 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Address: Department of Oceanography and Aisa-Pacific Ocean Reseach Center, National Sun Yat-sen University, 70 Lianhai Rd., Gushan, Kaohsiung 80424, Taiwan. Tel.: +886 7 525 2000x5028, + 886 7 525 5228; fax: +886 7 525 5228/5028. E-mail address: mhchen@mail.nsysu.edu.tw (M.-H. Chen). Marine Pollution Bulletin 85 (2014) 606–612 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul