Mercury Hazard Assessment for Piscivorous Wildlife in Glacier National Park

We examined the mercury hazard posed to selected piscivorous wildlife in Glacier National Park (GNP), Montana. Logging Lake was our focal site where we estimated the dietary mercury concentrations of wildlife (common loon [Gavia immer], American mink [Neovison vison], river otter [Lontra canadensis], and belted kingfisher [Megaceryle alcyon]) by assuming that fishes were consumed in proportion to their relative abundances. To evaluate if Logging Lake provided a suitable baseline for our study, we made geographic comparisons of fish mercury levels and investigated the distribution and abundance of high mercury fishes within GNP. We complimented our assessment by examining selenium:mercury molar ratios in fishes from Logging Lake and Saint Mary Lake. Our results suggest fish consumption does not imperil wildlife from Logging Lake based on published thresholds for adverse mercury effects, but some hazard may exist particularly if there is strong feeding selectivity for the most contaminated species, northern pikeminnow (Ptychocheilus oregonensis). The geographic comparisons of fish mercury levels, together with the distribution and abundance of high mercury fishes within GNP, suggest that Logging Lake provided a relatively protective baseline among our study lakes. Risk may be further reduced by the molar excess of selenium relative to mercury, particularly in the smaller fishes typically consumed by GNP wildlife. Our findings contrast with studies from northeastern US and southeastern Canada where greater mercury hazard to wildlife exists. An emergent finding from our research is that waterborne concentrations of methylmercury may provide limited insight into regional differences in fish mercury levels.

Stafford CP, Downs CC, Langner HW (2016) Mercury Hazard Assessment for Piscivorous Wildlife in Glacier National Park. Northwest Science 90: 450–469. Available:

The following people assisted with field sampling: Ben Keggi, Tess Kreofsky, Keith Joint, and Melvin Woody (GNP); Samantha Chilcote and Elizabeth McGarry (GNP volunteers); and Toby Tabor and Thad Tidzump (Blackfeet Fish and Wildlife Department). We thank Leo Rosenthal, (Montana Fish, Wildlife, & Parks) and Candy Schrank (Wisconsin Department of Natural Resources) for providing unpublished data, as well as Trevor Selch (Montana Fish, Wildlife, & Parks) for helping locate USEPA data from Upper Two Medicine Lake. Funding was provided by the NPS Cooperative Ecosystem Study Unit at the University of Montana and the Glacier National Park Conservancy.

Northwest Scientific Association

Northwest Science


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