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<br />""'r1" <br /> <br />0'01'614 <br /> <br />Colorado pikeminnow population is separated from the mouth of the Animas River by about 50 <br />miles of river that include five diversion dams. <br /> <br />Young-of-the- Year (YOY) <br />Larval Colorado pikeminnow hatch in about 1 or 2 weeks and then drift downstream from <br />spawning areas to nursery areas. These fish are typically found in shallow, low-velocity habitats <br />along shorelines, such as backwaters (Vanicek and Kramer 1969). Larval studies on the San Juan <br />River focused on the drifting portion oflarvallife history, and five larval Colorado pikeminnow <br />were collected in drift nets (Platania et al. 2000). Key habitats for larvae were not determined by <br />these studies. <br /> <br />Studies in the Green and Colorado rivers found that YOY Colorado pikeminnow (25 to 100 mm <br />total length [TL]) used backwater habitats almost exclusively (Holden 1977, McAda and Tyus <br />1984, Tyus and Haines 1991). Backwaters were typically found in relatively low-gradient, sand- <br />substrate reaches of these rivers. During the 7-year research period, autumn sampling of nursery <br />habitats was conducted each year (Archer and Crowl 2000a), and 22 wild YOY Colorado <br />pikeminnow were collected in the San Juan River (Platania et al. 2000). Most of these fish were <br />collected in backwaters in the relatively low-gradient, sand-substrate reach of the river at the <br />interface with Lake Powell (Reach I). The numbers of wild fish collected were too low to <br />adequately characterize San Juan River habitat use. In addition, wild YOY retention appeared low <br />in the upper river. These findings suggested that nursery habitat may be limited in the river. To <br />address habitat use and retention, YOY Colorado pikeminnow were stocked at Shiprock, New <br />Mexico, and Mexican Hat, Utah, in 1996, 1997, and 1998 (Trammell and Archer 2000). Nearly <br />3,000 ofthese fish were collected from 1996 to 1998 (Trammel and Archer 2000, Propst and Hobbs <br />2000), with about 60% collected from backwaters, 15% from pools, and 13% from pocket water <br />(Converse and Holden 1999). The YOY appeared to favor larger, deeper backwater habitats, and <br />these habitats were often associated with the mouths of secondary channels (Trammell and Archer <br />2000). This information showed that in the San Juan River, similar to other rivers, YOY <br />predominately used backwaters, but other low-velocity habitats were also used. <br /> <br />Although wild YOY Colorado pikeminnow were predominately found in the lower few miles of <br />the San Juan River, the hatchery-reared YOY remained throughout the river and some moved <br />downstream with storm-generated flow events (Trammell and Archer 2000). In 1997, 30 stocked <br />YOY Colorado pikeminnow were collected up to 8 miles above the Shiprock, New Mexico, <br />stocking site about I month after stocking (Propst and Hobbs 2000), indicating upstream as well <br />as downstream movement. Few stocked YOY were found in the canyon sections below and above <br />Mexican Hat, Utah, but they were found in the low-gradient reach in the lower 13 miles of the river <br />near the interface with Lake Powell. Retention of fish stocked at Shiprock, New Mexico, was I <br />highest in the upper river. ~ <br /> <br />3-8 <br /> <br />Program Evaluation Report <br /> <br />September 2000 <br />