7401

• UCREFRP Catalog Number: 7401
• Author: U.S. Bureau of Reclamation.
• Title: Ruedi Reservoir, Colorado Round II Water Marketing Program, Final Supplement to the Environmental Statement, Fryingpan - Arkansas Projects, Colorado.
• USFW Year: 1989.
• USFW - Doc Type: Billings, Montana.
• Copyright Material: NO

3.28
Nitella are especially prevalent in the Fryingpan River inlet and growths of
Elodea, Potamoqeton and mosses are dense in Bagley Creek Bay.
Zooplankton concentrations usually peak during July (Nesler, 1979).
Synchaeta was the dominant rotifer and Cyclops, Daphnia, and Bosmina were the
most abundant crustaceans.
The benthos of the deep portions of the reservoir is comprised mainly of
oligochaetes and chironomids (Finnell, 1977; Nesler, 1979). Benthic studies
conducted by ERT in October 1982 revealed that the macro invertebrate communities
of Ruedi Reservoir inlet and bay areas are variable (Appendix D, Tables D.7 and
C.8). Various species of chironomids and snails generally dominated the
samples. However, macro invertebrate densities ranged from 1,804/m2 in the
shallow area of Fryingpan inlet to 14,485/m2 in the deep area of Fryingpan inlet;
total biomass (wet weight) ranged from 0.93 g/m2 in the deep area of Gypsum Bay
to 25.5 g/m2 in the shallow area of Bagley Creek Bay. The communities were
representative of clean water and oligotrophic conditions.
Since late 1985, Mvsis relicta (opossum shrimp) have been found in the
Fryingpan River immediately below the Ruedi Dam outlet. Introduced to the
reservoir in 1970 as a fisheries management attempt to augment the supply of
nutrients in oxygen-rich lakes, the mysids became a viable population by 1983.
Release of the mysid shrimp through the Ruedi outlet works has provided a
tremendous food supply for the trout populations in the Fryingpan just below the
dam. Due to the appearance of the mysids, the size of the trout has increased
significantly (Nehring, 1988). Post-mysid growth is most evident in the first
one mile below the dam and is negligible 5 to 6 miles downstream.
Periphyton in the Fryingpan River consists mainly of diatoms and green
algae typical of cold, rapid streams (ERT, 1982a). Aquatic macrophytes are also
important primary producers in some areas of the Fryingpan River. Large beds
of Ranunculus aquaticus are present just below the dam and 7 miles downstream
of the dam (ERT, 1982a). Macrophyte beds can provide refugia for benthic
organisms and shelter for fish.
Longitudinal changes in the benthic community were noted in the Fryingpan
River downstream of the dam in August 1982 (ERT, 1982a). In October 1982 there
were fewer taxa and greater density and biomass of macro invertebrates immediately
below the dam compared to downstream sampling stations (Appendix B, Table B.6).
The community below the dam was dominated by the chironomid Pseudodiamesa, which
inhabits cold streams. Densities of this taxon declined in a downstream