FOOD BASE

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FoodbaseDiversity.jpg

The Aquatic Food Base below Glen Canyon Dam

The most abundant aquatic macroinvertebrates within the Glen Canyon reach include Gammarus lacustris (an introduced non-native amphipod), midges (order Diptera, family Chironomidae), snails (Physella sp. and Fossaria obrussa), segmented worms (especially Lumbricidae and Lumbriculidae) and other aquatic worms (Naididae and Tubificidae), fingernail clams in the family Sphaeriidae (Pisidium variable and P. walkeri), and the planarian Dugesia spp. (Blinn et al. 1992; Stevens, Shannon et al. 1997). Prior to 1995, snails were infrequently observed, but have since increased in abundance due to invasion by the non-native New Zealand mudsnail (Potamopyrgus antipodarum) (Valdez and Speas 2007; Cross et al. 2010). The mainstem Colorado River in Glen and Grand Canyons supports very few species or individuals of native mayflies, stoneflies, or caddisflies because of a combination of stressors, including altered temperature regimes and a pronounced varial zone (Stevens, Shannon, et al. 1997; Kennedy et al. 2016). Some tributaries of the Colorado River, along with backwaters and off-channel ponds, have higher diversity and densities of mayflies, stoneflies, and caddisflies compared to the mainstem. (2018 Expanded Non-Native Aquatic Species Management Plan EA)

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.

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

Updates


Aquatic macroinvertebrates found below Glen Canyon Dam

Gammarus lacustris: an introduced non-native freshwater shrimp (amphipod)
Midge (larvae)
Midge (adult)
Blackfly (larvae)


Links and Information

Foodbase Projects

Oviposition and Egg Desiccation Studies

Foodwebs and Bioenergetics Studies

Measuring Primary Production in the Lees Ferry Reach

The BugFlow Experiment

Citizen Science Insect Monitoring

Hyporheic Anoxia in the Lees Ferry Reach

Downstream Recovery of the Foodbase Community in Several Colorado River Tailwaters

Drift and Food Availability Studies

Foodbase PEP

Papers and Presentations

2018

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2016

2015

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1981

1959

Other Stuff

The interaction of fish, foodbase, and temperature

Fish occupying warmer water have higher metabolic demands than individuals in cooler water, and if these demands increase concurrently with a seasonal decline in prey availability, then growth rates may be reduced. [1]


  • 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.

Notably, several species of cold-tolerant nonnative invertebrates were intentionally introduced into the Colorado River after Glen Canyon Dam was closed in 1963. Altogether 10,000 immature mayflies were secured from a commercial source in Minnesota and released at three sites in the Lees Ferry reach. Also, 10,000 snails, 5,000 leeches, and thousands of insects representing at least 10 families were transported from the San Juan River in New Mexico to the river near Lees Ferry. In addition, 50,000 “scuds” (Gammarus lacustris) were introduced into Bright Angel Creek in 1932 and at Lees Ferry and below the dam in 1968, in addition to 2,000 crayfish taken from the LCR near Springerville, AZ (Blinn and Cole 1991). Gammarus lacustris has thrived in the cold, clear reaches below the dam, but the fate of the other introduced species is unknown.