Thursday, May 29, 2008 - 2:30 PM
567

Food web effects of a nonnative fish: Initial results of a large-scale field experiment

Joseph R. Benjamin1, Fabio A. Lepori2, Colden V. Baxter1, and Kurt D. Fausch2. (1) Stream Ecology Center, Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007, (2) Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, CO 80523

Nonnative species may have unforeseen effects on communities they invade, and impacts may propagate across habitat boundaries.  In streams, invading fish may deplete benthic insect consumers, causing not only increased periphyton, but reduce adult insect emergence and riparian spiders (Tetragnathidae).  We tested these hypotheses by manipulating the presence and density of nonnative brook trout and native cutthroat trout in a large-scale field experiment.  Treatments included enclosed reaches with either no fish (NF), brook trout at natural densities (0.4 fish/m2; BKNat), cutthroat trout at natural densities (0.15 fish/m2; CT), or brook trout at densities similar to CT (BKRed).  We expected BKNat to reduce the flux of emerging insects and tetragnathid abundance and increase periphyton biomass, NF to exhibit the opposite response, and CT and BKRed to have intermediate values.  Initial results suggest that, contrary to our hypotheses, the abundance of riparian spiders and periphyton was similar across treatments. However, samples from the end of the experiment indicate that trout affected insect emergence, with brook trout showing the strongest effects. Although further analysis will be necessary to identify the mechanisms involved, our results suggest that the replacement of native by non-native species can alter potentially important fluxes of organisms across ecosystems.


Web Page: nonnative species effects, large-scale experiment, stream-riparian food web

See more of Food Webs III
See more of Contributed Sessions

See more of The Nabs 56th Annual Meeting (25-28 May, 2008)