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backwaters with narrow river connections and a lower water exchange rate generally had higher zooplankton densities. River fluctuations that increased backwater water level imported riverine nutrients and POM (particulate organic matter) and resuspended organic material from their periphery. Concentrations of major nutrients (nitrate-N, ammonia-N, and phosphorus) generally increased in backwaters from upstream at Island Park to downstream at Ouray presumably due to an internal nutrient recycling within these backwaters or in response to attenuated riverflows. Attenuated river fluctuations may reduce the tendency for violent mixing of water in Ouray backwaters, and reduce export of POM and nutrients. Average macroinvertebrate dry biomass increased progressively downstream with greatest biomass in Ouray backwaters. Chironomid larvae predominated the benthic fauna and this food item was common in the diets of some fish <20mm TL (native and nonnative forms). Fourteen Colorado squawfish <20mm TL consumed mostly chironomid larvae while larger individuals were more piscivorous, consuming red shiner, fathead minnow, and occasional catostomids. (Authors abstract from Executive Summary) Study 6: Mapping of important backwater habitats of Colorado squawfish. Report 18- Comprehensive report (1986-1988) on the effects of Green River flows on backwater habitat availability as determined by remote sensing techniques. (Pucherelli and Clark 1989) Aerial photography and videography can be used successfully to determine backwater availability in the upper Colorado river basin in response to varying flow regimes. These techniques should also be applied to future riverine habitat monitoring programs for the Green and Colorado rivers. A flow range of 28.3 to 50.94 m /s at the USGS Jensen gauge will produce more backwater area and numbers on the upper Green River. Flows above 50.94 m3/s had a detrimental effect on backwater development under our study conditions. A gradually decreasing hydrograph during summer months appears to be a required condition for maximizing backwater availability. High flows may be required before young-of-the-year Colorado squawfish enter the system to maximize backwater availability. Backwaters are much more numerous and substantially larger in the Green River above Desolation Canyon than below it. The upper nursery area (Tyus et al. 1987) had the greatest amount of backwater habitat. (Conclusions) HABITAT USE AND STREAMFLOW NEEDS OF COLORADO SQUAWFISH, HUMPBACK CHUB, AND RAZORBACK SUCKER The following section summarizes the distribution, abundance, and habitat use of Colorado squawfish, humpback chub, bonytail chub, and razorback sucker in the Green River. Habitat requirements and factors limiting the distribution and abundance of each species were obtained from data presented in the preceding section and from a review of pertinent literature. Streamflow needs were determined from an evaluation of this information. 15