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<br />r <br /> <br />backwaters with narrow river connections and a lower water exchange rate <br />generally had higher zooplankton densities. River fluctuations that increased <br />backwater water level imported riverine nutrients and POM (particulate organic <br />matter) and resuspended organic material from their periphery. Concentrations <br />of major nutrients (nitrate-N, ammonia-N, and phosphorus) generally increased <br />in backwaters from upstream at Island Park to downstream at Ouray presumably <br />due to an internal nutrient recycling within these backwaters or in response <br />to attenuated riverflows. Attenuated river fluctuations may reduce the <br />tendency for violent mixing of water in Ouray backwaters, and reduce export of <br />POM and nutrients. Average macroinvertebrate dry biomass increased <br />progressively downstream with greatest biomass in Ouray backwaters. Chironomid <br />larvae predominated the benthic fauna and this food item was common in the <br />diets of some fish <20mm Tl (native and nonnative forms). Fourteen Colorado <br />squawfish <20mm Tl consumed mostly chironomid larvae while larger individuals <br />were more piscivorous, consuming red shiner, fathead minnow, and occasional <br />catostomids. (Authors abstract from Executive Summary) <br /> <br />Study 6: Mapping of important backwater habitats of Colorado squawfish. <br /> <br />Report 18- Comprehensive report (1986-1988) on the effects of Green River <br />flows on backwater habitat availability as determined by remote <br />sensing techniques. (Pucherelli and Clark 19B9) <br /> <br />Aerial photography and videography can be used successfully to determine <br />backwater availability in the upper Colorado river basin in response to <br />varying flow regimes. These techniques should also be applied to future <br />riverine habitat monitor~ng programs for the Green and Colorado rivers. A flow <br />range of 28.3 to 50.94 m Is at the USGS Jensen gauge will produce more <br />backwater area and numbers on the upper Green River. Flows above 50.94 m3/s <br />had a detrimental effect on backwater development under our study conditions. <br />A gradually decreasing hydrograph during summer months appears to be a <br />required condition for maximizing backwater availability. High flows may be <br />required before young-of-the-year Colorado squawfish enter the system to <br />maximize backwater availability. Backwaters are much more numerous and <br />substantially larger in the Green River above Desolation Canyon than below it. <br />The upper nursery area (Tyus et al. 19B7) had the greatest amount of backwater <br />habitat. (Conclusions) <br /> <br />HABITAT USE AND STREAMFLOW NEEDS OF COLORADO SQUAWFISH, HUMPBACK CHUB, <br />AND RAZORBACK SUCKER <br /> <br />The following section summarizes the distribution, abundance, and habitat <br />use of Colorado squawfish, humpback chub, bony tail chub, and razorback sucker <br />in the Green River. Habitat requirements and factors limiting the distribution <br />and abundance of each species were obtained from data presented in the <br />preceding section and from a review of pertinent literature. Streamflow needs <br />were determined from an evaluation of this information. <br /> <br />15 <br />