Ganther et al. ( 1972) reported that the mercury 

 to selenium molar ratio for high-mercury tuna 

 (can tuna) (average 2.87 mg/kg) approaches 0.5. 

 They also noted that the mercury and selenium 

 increments between low-mercury tuna (0.32 

 mg/kg) and high-mercury tuna were about in a 1 : 1 

 molar ratio, implying they are accumulated to- 

 gether. 



The total mercury-selenium relationships ob- 

 served in marine mammals and man are similar to 

 those found in tuna. Koeman et al. (1973) found a 

 1:1 molar ratio in the livers of seals, P/zoco vitu- 

 lina , porpoises, Phocoena phocoena , and dol- 

 phins, Tursiop truruatus, Delphinus delphis, 

 Lagenorhynchus obscurus, and Sotalia guianen- 

 sis. Regression analyses of their data give an av- 

 erage slope of 2. 7 ±0.2 or 1.1 ±0.1 on a molar basis 

 for mercury-selenium interactions (r = 0.932). In- 

 terestingly, they found that only 2 to 14^}^ of mer- 

 cury in the liver and 2 to 13^7^ in the brain was 

 recovered as methyl mercury. Post-mortem 

 studies on humans exposed to high inorganic mer- 

 cury (from a mercury mine) showed a 1:1 molar 

 ratio of mercury to selenium (/• = 0.998) in tissues 

 which had accumulated high amounts of mercury, 

 i.e., thyroid, pituitary, kidney, and brain (Kosta et 

 al. 1975). They noted, however, that this ratio did 

 not exist for a nonexposed group in which mercury 

 and selenium levels were insignificant. Elevated 

 mercury levels were apparently responsible for 

 increasing the selenium concentrations such that, 

 in many cases, the molar ratio of mercury to 

 selenium increments over normal levels ap- 

 proached 1:1 (selenium was low in the m.ine envi- 

 ronment: 1 mg/kg versus 100 mg/kg Hg — in con- 

 trast to the relative enrichment of selenium in the 

 diet of tuna and marine mammals). The levels of 

 methyl mercury in organs of the exposed group 

 were low, implying that no significant in vivo 

 methylation occurs in man. 



Because selenium is high in the marlin ( average 

 1.98 mg/kg in muscle, 17.47 mg/kg in liver, 23.42 

 mg/kg in kidney ), the possibility of selenium toxic- 

 ity should not be discounted. Aptly, though, mer- 

 cury has been shown to mitigate the toxicity of 

 selenium in rats and chicks (Pafizek et al. 1971; 

 Hill 1974). 



In an earlier study, it was indicated that cooking 

 did not remove either methyl or total mercury 

 from marlin fillets (Schultz and Crear 1976). 

 Higgs et al. ( 1972) have found that baking does not 

 remove selenium from flounder or chicken al- 

 though some loss was reported from boiling two 



vegetables. It does appear then that mercury 

 (muscle average 3.12 mg/kg) and selenium (mus- 

 cle average 1.98 mg/kg) concentrations in raw 

 fillet are representative of that in cooked fish. 



Ackn()\\ ledgments 



We thank Jerry A. Wetherall of the National 

 Marine Fisheries Service (NMFS) for performing 

 the statistical analyses for this study. Grateful 

 appreciation is also extended to Eriks Leitis of the 

 Hawaii Epidemiologic Studies Program, Univer- 

 sity of Hawaii, and the Water Resources Research 

 Center, University of Hawaii, for the use of the 

 atomic absorption spectrophotometer and 

 fluorometer. The authors also acknowledge the 

 helpful discussion with Susumu Nishigaki of the 

 Tokyo Metropolitan Research Laboratory of Pub- 

 lic Health. The NMFS Office of Resource Utiliza- 

 tion contributed to the financial support of this 

 project. 



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