FOOD BASE

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The Aquatic Food Base below Glen Canyon Dam The Colorado River below Glen Canyon Dam has been altered by dam-induced modifications to the river’s flow, temperature, and sediment supply. Nonnative species have also changed the natural system. Nonnative fish are thought to prey on and compete with native fish, including the endangered humpback chub (Gila cypha). These impacts have likely changed both the amount and sources of energy that fuel the aquatic food web and the flows of energy within the food web. Installation of the dam created a relatively clear, cool aquatic environment below the dam that now allows aquatic plants to capture the sun’s energy, and they in turn are now consumed by a few species, including scuds (Gammarus lacustris), midges (Family: Chironomidae), blackflies (Simulium arcticum), and New Zealand mudsnails (Potamopyrgus antipodarum). The first three species can provide food for both native and nonnative fishes, but fish cannot digest the New Zealand mudsnail. Desired Future Condition for the Aquatic Food Base The aquatic food base will sustainably support viable populations of desired species at all trophic levels. Assure that an adequate, diverse, productive aquatic foodbase exists for fish and other aquatic and terrestrial species that depend on those food resources.

EPT as Biologic Indicators of Stream Condition	Algae and Aquatic Macrophytes	Aquatic Macroinvertebrates

Updates Kennedy's 2016 Bioscience paper presents a conceptual model describing how hydropower flows could be limiting aquatic insect diversity and production by limiting the reproductive success of insects accustom to laying their eggs along the shoreline. It provides supporting data from an egg desiccation study done below Flaming Gorge Dam, light trap data collected in the Grand Canyon, and a comparison of fluctuation intensity and EPT diversity in several western US hydropower tailwaters. The paper concludes that egg desiccation from fluctuating flows is likely a leading factor in limiting aquatic insect diversity and production in tailwaters below hydropower facilities. The paper also proposes a bugflow experiment to be tested at Glen Canyon Dam as a possible mitigation for fluctuating flows made for hydropower production.

Links and Information GCMRC Aquatic Food Base Lab USU Buglab Foodbase Projects Measuring Primary Production in the Lees Ferry Reach Effects of BugFlows and HFEs on the Aquatic Foodbase The Bugflow Experiment Page Hyporheic Anoxia in the Lees Ferry Reach Downstream Recovery of the Foodbase Community in Several Colorado River Tailwaters Oviposition and Egg Desiccation Macroinvertebrate Oviposition (egg-laying) Habitat Preferences on the Green River below Flaming Gorge Dam Foodwebs and Bioenergetics Drift and Food Availability Responses of macroinvertebrate drift, benthic assemblages and trout foraging to hydropeaking Foodbase PEP 2001 Foodbase PEP 2004 Foodbase PEP Papers and Presentations 2017 Fluvial Aquatic Ecology of the Colorado River (… especially Lees Ferry) Floods, Flows and the Aquatic Foodbase PPT The Grand Beyond: Aquatic Foodbase of the Upper Colorado River Basin 2016 Grand Canyon Monitoring and Research Center Science Updates (BO Compliance, Trout Updates, Green Sunfish, Fisheries PEP, Partners in Science) Voichick et al. 2016. Water clarity of the Colorado River—Implications for food webs and fish communities: U.S. Geological Survey Fact Sheet 2016–3053, 4 p. Aquatic Foodbase of the Little Colorado River Kennedy et al. 2016. Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs. BioScience Food availability in the Little Colorado River over space and time A Life History Bottleneck for Aquatic Insects Arising from Load Following 2015 Invertebrate drift in Glen Canyon 2007-2013 2014 Citizen Science Insect Monitoring: A Powerful Tool for Detecting Ecosystem Change Science Updates - Recent Research on Sand, Bugs, and Fish Foodbase Enhancement Suggestions from Federation of Fly Fishers Foodbase Findings Low flows in Glen Canyon: preliminary geomorphic analysis of the potential effects on fish and food base (Melis) 2013 Miller and Judson. 2013. Responses of macroinvertebrate drift, benthic assemblages, and trout foraging to hydropeaking. Can. J. Fish. Aquat. Sci. 71: 675–687 GCMRC Update - Status of Resources and Sediment Conditions Macroinvertebrate diets reflect tributary inputs and turbidity-driven changes in food availability in the Colorado River downstream of Glen Canyon Dam Kennedy et al. 2013. The relation between invertebrate drift and two primary controls, discharge and benthic densities, in a large regulated river Annual Reporting Meeting: Foodbase Update 2012 Air –water oxygen exchange in a large whitewater river Temperatures, TCD, and Food Base 2011 Ecosystem ecology meets adaptive management: Food web response to a controlled flood on the Colorado River, Glen Canyon Secondary production rates, consumption rates, and trophic basis of production of fishes in the Colorado River, Grand Canyon, AZ: An assessment of potential competition for food Diet overlap and competition among native and non-native small-bodied fishes in the Colorado River, Arizona 2010 Resource composition and macroinvertebrate resource consumption in the Colorado River below Glen Canyon Dam Short-Term Effects of the 2008 High-Flow Experiment on Macroinvertebrates in Colorado River Below Glen Canyon Dam, Arizona Basal Resources in Backwaters of the Colorado River Below Glen Canyon Dam—Effects of Discharge Regimes and Comparison with Mainstem Depositional Environments Aquatic production and carbon flow in the Colorado River Pages 105-112 in Proceedings of the Colorado River Basin Science and Resource Management Symposium, November 18–20, 2008, Scottsdale, Arizona Invasion and production of New Zealand mud snails in the Colorado River, Glen Canyon 1999 Watershed influence on the macroinvertebrate fauna of ten major tributaries of the Colorado River through Grand Canyon, Arizona 1991 Zooplankton of the Colorado River: Glen Canyon Dam to Diamond Creek 1988 The utilization of Cladophora glomerata and epiphytic diatoms as a food resource by rainbow trout in the Colorado River below Glen Canyon Dam, Arizona 1981 A survey of the aquatic flora and fauna of the Grand Canyon 1959 Ecological Studies of the Flora and Fauna in Glen Canyon (Woodbury 1959) Other Stuff Caddis hatch below Parker Dam. There are several species of EPT below Parker and Davis Dam in spite of daily fluctuations that exceed 6 feet per day. Macroinvertebrate egg masses on the Green River below Flaming Gorge Dam Black Flies and Midges fuel fish production below Glen Canyon Dam. Black Flies and Midges respond positively to spring HFE's. Mud Snails were introduced below Glen Canyon Dam around 1995.