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6/07/2017 | 9:00 AM - 9:15 AM | MISMATCH BETWEEN BENTHIC MACROINVERTEBRATE DENSITIES AND STABLE ISOTOPES OF FISHES IN DYNAMIC HIGH-HEAD RESERVOIRS IN THE WILLAMETTE RIVER BASIN, OREGON. | 306C
MISMATCH BETWEEN BENTHIC MACROINVERTEBRATE DENSITIES AND STABLE ISOTOPES OF FISHES IN DYNAMIC HIGH-HEAD RESERVOIRS IN THE WILLAMETTE RIVER BASIN, OREGON.
How do seasonally fluctuating reservoir water levels affect the availability of benthic invertebrates vs. zooplankton as prey for fishes? The Willamette River Basin, Oregon is impounded by high-head dams that undergo water level fluctuations, exposing much of the sediments. We examined the littoral benthic macroinvertebrate community, zooplankton, and fishes including juvenile Chinook Salmon, Bluegill, Largemouth Bass and crappie at three such reservoirs (Fall Creek, Hills Creek and Lookout Point). We found very low densities of benthic macroinvertebrates (generally < 25/m2), dominated by Chironomidae. Stable carbon isotope ratios of benthic macroinvertebrates were variable across families, but were enriched compared to those of zooplankton. Although observed macroinvertebrate densities were very low and gut contents of fishes suggested that Daphnia are their dominant food source, the relatively enriched carbon isotope ratios of fishes suggest a major macroinvertebrate contribution to their diets. We explore hypotheses to explain this mismatch of low observed macroinvertebrate densities with their apparent dietary importance to fishes, as suggested by isotopic ratios.
- C36 Water Resource Management
- C03 Invertebrates
- C07 Lentic Ecology & C03 Invertebrates
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Presenters/Authors
Christina Murphy
(), Oregon State University, Department of Fisheries & Wildlife, christina.murphy@oregonstate.edu;
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Ivan Arismendi
(), Oregon State University, Department of Fisheries & Wildlife, ivan.arismendi@oregonstate.edu;
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Stephen K. Hamilton
(), Michigan State University, hamilton@kbs.msu.edu;
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Sherri Johnson
(), U.S. Forest Service, Pacific Northwest Research Station, sherrijohnson@fs.fed.us;
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