FOOD BASE

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Food Base USGS- GCMRC DefinitionThe 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.

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Information USGS- GCMRC Aquatic Food Base Link Reports and Links 2016 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 Foodbase Enhancement Suggestions from Federation of Fly Fishers Foodbase Findings Foodbase Update 2013 Food-web dynamics in a large river discontinuum Native and nonnative fish populations of the Colorado River are food limited - Evidence from new food web analyses Macroinvertebrate diets reflect tributary inputs and turbidity-driven changes in food availability in the Colorado River downstream of Glen Canyon Dam The relation between invertebrate drift and two primary controls, discharge and benthic densities, in a large regulated river 2012 Ecosystem ecology meets adaptive management: food web response to a controlled flood on the Colorado River, Glen Canyon Air –water oxygen exchange in a large whitewater river 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, GRAND CANYON, 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 Other Stuff Black Flies and Midges fuel RBT growth. Black Flies and Midges respond positively to HFE's Mud Snails were introduced to the system around 1995. Temperatures/ TCD on Food Base: Benthic algae and invertebrates that form the fish food base are adapted to constatn, cold water temperatures. They may not be able to withstand cycling between warm and cold temperatures. (pg23) GCMRC scientists and their university cooperators (University of Wyoming, Idaho State University, and Loyola University, Chicago) are studying the kinds of organic matter (for example, algae and leaf litter) and invertebrate communities (for example, black flies and bloodworms (Families: Lumbricidae and Tubificidae)) in the Colorado River below Glen Canyon Dam and how the sun’s energy is captured and passed from one species to another. Collectively, organic matter and the aquatic invertebrates that consume it largely constitute the food base for fish in the Colorado River ecosystem. Current research efforts focus on the temporal patterns, multi-year trends, and factors that affect the amount and sources of food for humpback chub and rainbow trout (Oncorhynchus mykiss). This information is used to understand the role that food plays in determining the distribution, population density, and growth of these animals. A better understanding of the aquatic food web of the Colorado River will allow natural resource managers to describe the conditions that would be expected to support the Grand Canyon population of humpback chub, the economically important Lees Ferry trout fishery, and other fish species. Red Orbit - Lessons From The Grand Canyon: Dams Destabilize River Food Webs