Rapid food web recovery in response to removal of an introduced apex predator

Abstract

Non-native species have increased extinction rates, decreased diversity, altered organism distributions, and constrained ecosystem functioning in native aquatic and terrestrial communities. Although widespread fish introductions have dramatically altered fish communities in north temperate lakes, restoration of native fish communities has been rarely accomplished. This study evaluated a native fish community restoration using a stable isotope based metric. Stable isotopes from a native apex predator (lake trout (Salvelinus namaycush)) were used to measure food web changes following removal of a dominant non-native apex predator (smallmouth bass (Micropterus dolomieu)). Prior to bass removal, lake trout consumed primarily invertebrates. Within 2 years of the initiation of an experimental removal effort, lake trout δ13C values(–25.9‰ to –24.9‰) and trophic position (3.5–3.9) increased, reflecting a switch to prey fish consumption that was supported by stomach contents analyses. Here, we show the rapid reestablishment of food web linkages within a native fish community in response to changes in principal energy sources and trophic position of a native apex predator along with the ability to quantify the extent of these changes.