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depth was measured, and a 63f.1, 20.32 cm diameter plankton tow net was lowered into the water and allowed to settle at the bottom of the backwater for 60 seconds. After the haul was completed, the net was rinsed and plankton were concentrated in the collecting cup. Samples were fixed in whirlpaks with 70% EtOH. The tow net was cleaned with filtered water (63 f.1 mesh) after each sample. Five vertical hauls were also taken in the same manner at Anderson Bottom during the night to determine if nocturnal zooplankton migrations were occurring. Core samples were taken in the same general area as the plankton samples though these were limited by the height of the core sampler after river flows increased. Each sample was collected with a benthic coring device supplied by Dr. Dennis Shiozawa at Brigham Young University. The sampler was an 18.5mm diameter clear acrylic tube attached to a 1.27 m conduit pipe with an attached handle, plunger and tube stopper. The coring device was lowered into the benthos in the unstoppered position and then plunged to seal the tube thereby preventing sediment loss as the sample was brought to the surface. Samples were measured, released into Falcon centrifuge tubes, and fixed in 70% EtOH. Abiotic measurements Water temperature, depth and time were recorded at 5 cm and 122 cm (or bottom of the backwater in lower water), at all sites and sampling dates. No set pattern for sampling each backwater from week to week was followed, so that each site was sampled randomly in either the morning or afternoon hours. Daily mean river flow values, recorded in cubic feet per second, were obtained from the U.S.G.S. station at Green River, UT. Conductivity, pH, dissolved oxygen and Secchi disk readings were recorded after five weeks of biological sampling (Appendix I). Laboratory processing In the laboratory, a sample was poured onto a 63f.1 sieve under running water. Sand and clay particles were broken up and large detritus particles were rinsed into the sample and examined under the microscope before discarding. Samples were then collected into 3 dram glass specimen vials with 70% EtOH. Rose bengal stain was added to aid in detecting organisms during sorting. Four major taxa (Nemotoda, Oligochaeta, Rotifera, and Copepoda) and 13 minor taxa (Cladocera, Ostrocoda, Ceratogogonidae, Chironomidae, Tardigrada, Plecoptera, Ephemeroptera, Hydracarina, Simuliidae, Collembola, Coelenterata (hydroids), Tipulidae and Culicidae) were quantified. Copedpoda were broken into three categories: adults, copepodids and nauplii. 4