Recent research on non-native species introductions in aquatic food webs has emphasized impacts on food web interactions. In this study, we compare food web impacts of an introduced predatory gamefish (Salvelinus namaycush) and an invertebrate (Mysis relicta) on the food web structure of Lake Tahoe (USA). Specimens spanning a 126 year period were measured for carbon and nitrogen stable isotopes to determine their trophic niche pre- and post-establishment. Introduction of the predatory gamefish did not result in major shifts in energy flow pathways through the food web, although there have been documented top down impacts on native trout and forage fishes. In comparison, introduction of Mysis represents the insertion of a new species into the middle of the food web. We found that Mysis introduction significantly restructured food web energetics, as evidenced by changes in the trophic niche of fish species from both benthic and pelagic habitats. Prior research showed strong alterations of zooplankton community structure resulting from Mysis predation. These ecosystem-altering impacts of invertebrate invaders are of particular concern because of the onslaught of invertebrate invaders colonizing North American lakes, particularly the Laurentian Great Lakes. Since invertebrate introductions are difficult to reverse, preventing the spread of invertebrate invaders should be a priority for lake managers
Species 1: Salmoniformes Salmonidae Salvelinus namaycush
Species 2: Mysidacea Mysidae Mysis relicta
Keywords: Stable isotopes, aquatic food web
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