256 EISLER 



Several observations can be made regarding mercury residues in 

 teleosts collected in the field. First, mercury tends to concentrate in 

 the edible flesh of finfish, with older fish containing more mercury 

 per unit weight than young fish (Alexander et al., 1973; Barber, 

 Vijayakumar, and Cross, 1972; Cross et al., 1973; Cumont et al., 

 1972; DeClerk, Vanderstoppen, and Vyncke, 1974; Evans, Bails, and 

 D'ltri, 1972; Forrester, Ketchen, and Wong, 1972; Giblin and 

 Massaro, 1973; Greichus, Greichus, and Emerick, 1973; Hannerz, 

 1968; Johnels and Westermark, 1969; Johnels etal., 1967; Kleinert 

 and Degurse, 1972; Knight and Herring, 1972; Nuorteva and 

 Hasanen, 1971; 1975; Peterson, Kalwe, and Sharp, 1973; Scott and 

 Armstrong, 1972; Svansson, 1975; Taylor and Bright, 1973; 

 Vermeer, 1972). Second, most of the mercury in fish flesh was in the 

 organic form, primarily methyl mercury (Fukui et al., 1973; Kamps, 

 Carr, and Miller, 1972; Koeman etal., 1973; Peterson, Kalwe, and 

 Sharp, 1973; Rissanen, Erkama, and Miettinen, 1972;Westoo, 1966; 

 1969; 1973; Zitko etal., 1971). Third, levels of mercury in muscle 

 from adult tunas, billfishes, sharks, and other carnivores were higher 

 than those in young fishes with a shorter food chain; this indicates 

 associations among predatory behavior, longevity, and mercury 

 accumulation (Forrester, Ketchen, and Wong, 1972; Jernelov, 1972; 

 Peakall and Lovett, 1972; Peterson, Kalwe, and Sharp, 1973; 

 Ratkowsky, Dix, and Wilson, 1975; Saila, 1971; Ui, 1972; Walter, 

 June, and Brown, 1973). Finally, elevated levels of mercury in 

 wide-ranging oceanic fish are not solely the consequence of anthro- 

 pogenic activities but also result from natural concentrations as well 

 (Greig, Wenzloff, and Pearce, 1976; Miller et al., 1972; Schultz et al., 

 1976). 



Birds that feed on aquatic animals exhibit markedly increased 

 concentrations of mercury in comparison with terrestrial raptorial 

 species (Johnels and Westermark, 1969; Karppanen and Henriksson, 

 1970). Top trophic-level predators, such as cormorants and pelicans, 

 demonstrated mercury concentration factors in their flesh of 14- and 

 6-fold, respectively, over prey fish (Greichus, Greichus, and Emerick, 

 1973). Mercury levels in aquatic and fish-eating birds were elevated 

 in the vicinity of chlor— alkali plants where mercury is used as a 

 catalyst (Fimreite, 1974; Fimreite etal., 1971); these differences 

 were detectable up to 300 km from the chlor— alkali plant (Fimreite 

 and Reynolds, 1973). Eggs of fish-eating birds, including herons and 

 grebes, collected near mercury point-source discharges contained 

 abnormally high levels of mercury; 29% of eggs contained more than 

 0.5 mg/kg wet weight, and 9% contained more than 1.0 mg/kg 

 (Faber and Hickey, 1973). Seasonal variations in mercury levels 



