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AQUATIC INVERTEBRATE RESPONSE TO TROUT REMOVAL IN BRIGHT ANGEL CREEK, GRAND CANYON, AZ

Top predators often act as keystone species, and their removal from an ecosystem can trigger trophic cascades, affecting all levels of the food web. In Bright Angel Creek, a tributary to the Colorado River in Grand Canyon, the National Park Service is concluding a five-year effort to mechanically remove introduced top predators, brown trout and rainbow trout from the stream. We evaluated the effects of nonnative fish suppression on food web dynamics and macroinvertebrate resource availability to native fish species. We collected benthic, drift and emergent adult samples seasonally throughout a 3.2 km trout removal reach and compared results to a baseline study conducted prior to trout removal. We predict that invertebrate community response to trout removal will manifest as an increase in predatory insects and a decrease in collector-gatherer insects consistent with a trophic cascade. By exploring the consequences of trout removal on the food web, our results will aid managers in better understanding the ecosystem-wide effects of nonnative fish within Bright Angel Creek, and in assessing the suitability of the stream for potential native endangered species reintroduction.

Megan Daubert (Primary Presenter/Author), USGS Grand Canyon Monitoring & Research Center , mdaubert@usgs.gov;


Ted Kennedy ( Co-Presenter/Co-Author), USGS Grand Canyon Monitoring and Research Center, tkennedy@usgs.gov;


Jeffrey Muehlbauer ( Co-Presenter/Co-Author), USGS Grand Canyon Monitoring and Research Center, jmuehlbauer@usgs.gov;


Brian Healy ( Co-Presenter/Co-Author), National Park Service, brian_healy@nps.gov;