9505

• UCREFRP Catalog Number: 9505
• Author: Cooper, D. J. and C. Severn.
• Title: Wetlands of the Escalante State Wildlife Area on the Gunnison River, Near Delta, Colorado
• USFW Year: 1994.
• USFW - Doc Type: Hydrology, Water Chemistry, Vegetation, Invertebrate Communities, and Restoration Potential.
• Copyright Material: NO

Invertebrates
Introduction
Recent research indicates that several invertebrate taxa
are important to larval and juvenile fish. The Chironomidae
family of the Order Diptera and the Orders Cladocera and Copepoda
of the Class Crustacea 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, river channel, and river
backwater communities were sampled for invertebrates at this
site. The 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, Cnidaria, 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. Benthos 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'2
for benthic invertebrates. Benthic samples were collected to a
29