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<br />a <br />l:,,":;t <br />C...:J <br />\ .~ <br /> <br />5 <br /> <br />CJ nursery habitat, result in limited recruitment. The goal of evaluation of habitat for Age-O <br />--.1 Colorado sQuawfish has several objectives: <br /> <br />1. To empirically monitor the annual recruitment of young-of-year Colorado <br />squaw fish in relation to flow patterns in the San Juan River. <br /> <br />2. To determine the Quality and Quantity of low-velocity habitats in the San Juan <br />River for use by Colorado sQuawfish by experimentally stocking young-of-year <br />fish. <br /> <br />3. To determine the effects of diversion canals on young-of-year Colorado <br />sQuawfish drift/movement (e.g., stranding, etc.). <br /> <br />4. To characterize the early-life stage ichthyofaunal community in low-velocity <br />(nursery) habitats. <br /> <br />5. To characterize nursery habitats and their use in the San Juan River system. <br /> <br />6. To determine overwinter survival of experimentally stocked Age-l sized <br />(approximately 70-90 mm) Colorado sQuawfish. <br /> <br />7. To determine what habitats juvenile Colorado sQuawfish utilize. <br /> <br />8. To determine spray marking mortality and spray marking retention. <br /> <br />The Colorado squawfish was listed as endangered on March 11. 1967. Habitat alteration, <br />fragmentation, and degradation arising from dam construction; and competition and predation <br />from introduced non-native fishes have been cited as the major factors responsible for the <br />decline of the species. As a top level predator, the Colorado squawfish may experience <br />bioaccumulation of contaminants from its prey. <br /> <br />The Colorado sQuawfish evolved as the main predator in the Colorado River and San Juan <br />River systems. The diet of Colorado sQuawfish longer than 3 or 4 inches consists almost <br />entirely of other fish-es (Vanicek and Kramer 1969). The Colorado sQuawfish is the largest <br />cyprinid (minnow family) native to North America and, during predevelopment times, may <br />have grown as large as 6 feet in length and weighed nearly 100 pounds (Behnke and Benson <br />1983). These large fish are known to be long-lived and may reach 25-50 years of age. The <br />Colorado squawfish currently occupies about 1,030 river miles in the Colorado River system <br />(20 percent of its original rangel and natural populations are currently found only in the San <br />Juan and other subbasins above Glen Canyon Dam (Tyus and Karp 1990). <br /> <br />Based on early fish collection records, archaeological finds, and other observations, the <br />Colorado sQuawfish was once found throughout warm water reaches of the entire Colorado <br />River Basin, including reaches of the upper San Juan River and possibly its major tributaries. <br />Colorado sQuawfish were apparently never found in colder headwater areas. Seethaler (1978) <br />indicated that the species was abundant in suitable habitats throughout the entire Colorado <br />River Basin prior to the 1850's. Platania and Young (1989) summarized historic fish <br />