Mercury in Fishes and Their Diet Items from Flathead Lake, Montana

Mercury levels in lake trout Salvelinus namaycush, lake whitefish Coregonus clupeaformis, and benthic invertebrates were investigated in Flathead Lake, Montana. For both fish species, mercury increased with size and age and showed a negative relationship with growth rate. No gender-based differences in mercury levels were observed for either lake trout or lake whitefish. A positive relationship between mercury concentration and depth was documented for lake trout and the pooled invertebrate sample, suggesting that individual lake trout have some long-term habitat preferences. In general, these findings underscore the need to consider biological attributes of organisms when conducting contaminant assessments and illustrate the usefulness of contaminants as food web tracers.