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<br />by CDOW), and the channel maintenance monitoring program (data to be provided by <br />USFWS). The participants will also detennine, based on snowpack and water supply <br />conditions) whether to attempt to operate to attenuate peakflow or to provide a channel <br />maintenance flow during spring runoff. <br /> <br />III. DESCRIPTION OF RESOURCES <br /> <br />A. Trout Fisheries <br /> <br />1.. Resource Overview <br /> <br />The mainstem of the South Platte River represents one of the more important and heavily <br />used fisheries in the state. Rainbow and brown trout comprise the vast majority of trout <br />biomass in this reach. Rainbow and brown trout are imported sport game fish that are not <br />naturally adapted to the streamflow and habitat in Colorado. Rainbow trout are most <br />common below Cheesman Reservoir in the Cheesman Canyon segment of the river where <br />they have, until recently, maintained self-sustaining populations with very high biomass. <br />In fact, these areas are considered "world classtl fisheries and are designated as Gold <br />Medal waters~ Unfortunately, the rainbow trout are declining in this area due to infection <br />by whirling disease~ Apparently this affects juvenile rainbow trout during the first year of <br />their life.. Recent data indicate that rainbow trout biomass in Cheesman Canyon is <br />declining and that there has been little recruitment of the younger year classes over the <br />past several years. There has been little impact on brown trout below Cheesman, and <br />there have not been any reported whirling disease impacts to either rainbow or brown <br />trout below Eleven Mile Reservoir. <br /> <br />In the past the area of interest has been stocked with rainbow trout, except for Cheesman <br />and Wildcat canyons. <br /> <br />In rivers such as the South Platte, where fishing harvest is limited by special regulations, <br />trout population fluctuations from year to year are related largely to habitat availability, <br />changing environmental conditions, diseases, streamflow, and to a lesser extent, stream <br />temperature. Streamflow related bottlenecks to trout populations generally occur during <br />extreme streamflow conditions, either the high flow period during spring runoff or the <br />low flow winter period. <br /> <br />2. Spinney Mountain to Eleven Mile Reservoir <br /> <br />The primary sportfish species managed in this reach are brown and rainbow trout. <br />Northern pike, snake river cutthroat trout and kokanee are periodically sampled in this <br />reach, but these species are not used to sustain riverine fishery management goals. Non- <br />sportfish species include western white and longnose suckers (native to South Platte <br />drainage). Brown trout maintain a self-sustaining population in this reach. Rainbow <br /> <br />N :\Supply\ Wa age\wildscen\attachb. doc <br /> <br />B...17 <br />