Total Mercury Residues in Livers and Eggs of Oldsquaws

Abstract

Total mercury was determined in 99 oldsquaw (Clangula hyemalis) livers and 11 composite clutches collected on Lake Michigan and in northwest Hudson Bay. Residue levels were similar in different sex and age-classes collected during the same time period on Lake Michigan. Mercury levels were higher in oldsquaws collected in Hudson Bay than in those taken on Lake Michigan. Residues in the hen and clutch were positively correlated. Mercury in duckling livers was negatively correlated with the weight of the liver. J. WILDL. MANAGE. 40(4):704-709 Studies on mercury residues in waterfowl generally have indicated fish-eating ducks contain higher mercury residues than invertebrate feeders, whereas vegetarian ducks usually showed relatively low mercury levels unless they had been feeding on mercury-treated grain (Vermeer and Armstrong 1972, Vermeer et al. 1973). Our work on the oldsquaw (Ellarson 1956, Peterson and Ellarson, unpublished data) indicated, for several reasons, this species would be suitable for monitoring mercury residues and other environmental toxicants. First, oldsquaws arrive on Lake Michigan in late November or early December and remain there until they migrate north in April and May. Therefore, any detectable changes in contaminant body burdens presumably would have come from within the lake's ecosystems. Second, the sexes are readily distinguishable and ageclasses can be determined. Third, while on Lake Michigan, oldsquaws eat essentially one invertebrate, Pontoporeia affinis, a deepwater bottom-dwelling amphipod (Peterson and Ellarson, unpublished data). The authors thank E. Ellefson and other commercial fishermen on Lake Michigan for saving birds caught in their gill nets. Appreciation is extended to R. G. Williamson, Arctic Research and Training Center at Rankin Inlet, NWT, for allowing us to use the Center's facilities during our arctic survey. Acknowledgment is made to the Toxic Chemicals Section of the Canadian Wildlife Service and the Wisconsin Department of Natural Resources for financial support in the determinations. This study was financed in part by the National Oceanic and Atmospheric Administration's Office of Sea Grant, Department of Commerce, through an institutional grant to the University of Wisconsin.