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<br />~ <br />( <br /> <br />r- <br /> <br />Methodology For Developing Recommendation - "Cool Water" Fisheries <br /> <br />. <br /> <br />The Bureau of Land Management (ELM) consulted with the Division of Wildlife (DOW) <br />regarding instream flow recommendations for "cool water" fishery streams in western Colorado. <br />These stream segments have the following characteristics: <br /> <br />. They are located between 4,000 and 7,500 feet in elevation <br />. They are located downstream from he3dwaters stream segments that are higher in <br />elevation and which support cold-water, salmonid fisheries. <br />. Sununer water temperatures frequently exceed 18 degrees Celsius, and occasionally <br />exceed 24 degrees Celsius. <br />. Lower gradient creates a higher ratio of pool to riffle habitat than in higher elevation, <br />cold water streams. <br />. Most the fish biomass is comprised of speckled dace, white sucker, flannelmouth <br />sucker, and bluehead sucker. Other sucker species and mottled sculpin may be present in <br />limited numbers. <br />. Salmonids are present in very limited numbers when they use the cool water habitat for <br />refuge from high flow events and icing events. Salmonids may also use the cool water <br />habitat for passage between cold water habitats. For example, when late sununer low <br />flows stress the salmonid population, tl1e salmonids may descend to a cool water <br />confluence of two tributaries in order to ascend to the cold water habitat in a parallel <br />tributary with higher flows. <br /> <br />. <br /> <br />The purpose of the consultation was to determine the suitability of using the wetted perimeter, <br />depth, and velocity criteria associated with the R2Cross model for "cool water" fishery <br />recommendations. An initial determination was made that the R2Cross model, which analyzes <br />riffle habitat, is a suitable model for these species. Riffle habitat is important for all of the species <br />listed above for various life stages, and for passage between pool habitats. An assumption was <br />made that if flows through riffles are protected, key pool habitat will be protected by these flow <br />levels as well. . <br /> <br />A discussion of each of these R2Cross criteria follows: <br /> <br />Wetted Perimeter - DOW and BLM agreed that the 50% wetted perimeter criteria should not <br />be altered for cool-water fisheries. This is cOllsidered the "foundation" criteria, because all <br />species must have sufficient quantities of physical habitat to execute all of their life stages, and to <br />have sufficient habitat for feeding. Adopting a criteria ofless than 50% wetted perimeter would <br />force undesirable competition among fish species for limited food supplies and reproductive areas, <br />and would reduce the diversity of fish species found in those streams. <br /> <br />Depth -- For tl1e species which comprise the rTlajority offish biomass, BLM and DOW consulted <br />the "Category 2" habitat suitability curves fOUlld in Edwards, E. A., H. Li, C. B. Schreck, 1983. <br />Habitat Suitability Index Models for Longnose Dace, United States Department of Interior, Fish <br />& Wildlife Service - FWSOBS-82/10.33; and in U.S. Fish & Wildlife Service Curve Library - Fort .. <br />Collins, CO, Item 120, File R. These curves suggested depths ranging from 0.8 to 2.6 feet for V <br />