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Invertebrates Introduction Recent research indicates that several invertebrate taxa -are important to larval and juvenile fish. The Chironomidae-and the Crustaceans Cladocera and Copepoda are important food for these fish. Grabowski and Hiebert (1988) analyzed stomach contents from many species of fish at different developmental- - stages. Their work was performed during 1987-88 on the Green River in backwater and riverine habitats from Island Park to Ouray National Wildlife Refuge. They reported that chironomids were by far the most frequently encountered prey in the stomachs. of all the fish studied.. A study conducted by Marsh and Langhorst (1988) of wild larval razorback suckers diet in-Lake Mohave and an adjacent backwater at Arizona Bay found that Cladocera .and Copepoda made up a greater frequency of the diet than other available taxa. This study, which occurred in a lentic as opposed to the lotic environment studied by Grabowski and Hiebert, also found a greater selection of Cladocera than Copepoda in relationship to availability. A key objective of the present study was to determine the suitability of study wetlands along, the Colorado,- Green, and. Gunnison Rivers as habitat for rearing endangered fish. Three .key aspects of habitat suitability-are hydrologic regime, ' chemical ,environment .and .food availability. The hydrology and .water chemistry variables were discussed above, and this section discusses the availability of food. Bulrush, open water-aquatic and other wetland communities .occurring on each. site as .well as river channel and river backwater communities.were,sampled.for.invertebrates. Thee river community was used as a control to compare food resources available in the channel to those in-other communities. .Our analyses emphasize the following water column invertebrate groups: 1) Cladocera, 2) Copepoda, 3) Chironomidae, 4) all .other insects less the Chironomidae, and 5) all-other invertebrates which include Gastropoda, Hydra, Nematoda,-and Protozoa. Taxonomic divisions presented for benthic invertebrates are: 1) Chironomidae-.and 2) other invertebrates -which include Gastropoda, Nematoda, Odonata, Hemiptera, Ephemeroptera, Coleoptera, and Culicidae. Water column-invertebrate data is typically .reported as number L`1 while benthic invertebrate densities are typically: reported as number m-2. Benthic data-was converted to a volume basis so that the two strata can be compared. -When applicable two Y axes are displayed to include-both number L'1 and number m_Z for benthic invertebrates. Benthic samples were collected to a-depth of 2 cm. A liter of this material would comprise an area 39