title: Changes in mercury bioaccumulation in an apex predator in response to removal of an introduced competitor.
abstract: We evaluated methylmercury (MeHg) concentrations in native apex predators, lake trout Salvelinus namaycush before and after the large-scale removal of introduced predators, smallmouth bass Micropterus dolomieu in a 270 ha Adirondack lake. Previous studies show that removing competitors can result in increased growth and decreased mercury concentrations in remaining fish. Instead, we observed a significant increase in lake trout MeHg concentrations despite observed increases in lake trout growth. Bioenergetics simulations predicted similar increases in lake trout MeHg concentrations. Higher MeHg in prey fish (post-removal diet) relative to invertebrates (pre-removal diet) was the most important factor increasing lake trout MeHg concentrations. However, this effect was counteracted by increased lake trout growth (i.e., growth dilution) likely due to a combination of decreased foraging costs and an increase in prey energy density. These data provide evidence for a mechanism (diet shift due to reduced competition) by which changes in food web structure can influence MeHg concentrations in top predators.
authors.affiliation: Warner College of Natural Resources, Colorado Cooperative Fish & Wildlife Research Unit, Colorado State University, Fort Collins, CO 80523, USA. jmlepak@lamar.colostate.edu
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Lepak
authors.forename: Jason M
authors.initials: JM
authors.lastname: Robinson
authors.forename: Clifford E
authors.initials: CE
authors.lastname: Kraft
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Josephson
mesh_terms: D000818:Animals; D001492:Bass / Q000378:metabolism / Q000502:physiology; D044822:Biodiversity; D003198:Computer Simulation; D004734:Energy Metabolism; D020387:Food Chain; D005618:Fresh Water; D008767:Methylmercury Compounds / Q000378:metabolism*; D008954:Models, Biological; D009518:New York; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior; D014337:Trout / Q000254:growth & development / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical