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<br />C) <br />C') <br />...... <br />co Colorado pikeminnow population is separated from the mouth of the Animas River by about 50 miles of <br />00 river that include five diversion dams. <br />c) <br /> <br />Young-of-the-Year (YOY) <br />Larval Colorado pikeminnow hatch in about 1 or 2 weeks and then drift downstream from spawning areas <br />to nursery areas. These fish are typically found in shallow, low-velocity habitats along shorelines, such as <br />backwaters (Vanicek and Kramer 1969). Larval studies on the San Juan River focused on the drifting <br />portion oflarvallife history, and five larval Colorado pikeminnow were collected in drift nets (platania et <br />al. 2000). Key habitats for larvae were not determined by these studies. <br /> <br />Studies in the Green and Colorado rivers found that YOY Colorado pikeminnow (25 to 100 mm total <br />length [TL]) used backwater habitats almost exclusively (Holden 1977, McAda and Tyus 1984, Tyus and <br />Haines 1991). Backwaters were typically found in relatively low-gradient, sand-substrate reaches of these <br />rivers. During the 7-year research period, autumn sampling of nursery habitats was conducted each year <br />(Archer and CrowI2000a), and 22 wild YOY Colorado pikeminnow were collected in the San Juan River <br />(platania et al. 2000). Most of these fish were collected in backwaters in the relatively low-gradient, sand- <br />substrate reach of the river at the interface with Lake Powell (Reach 1). The numbers of wild fish collected <br />were too low to adequately characterize San Juan River habitat use. In addition, wild YOY retention <br />appeared low in the upper river. These findings suggested that nursery habitat may be limited in the river. <br />To 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 3,000 <br />of these fish were collected from 1996 to 1998 (Trammel and Archer 2000, Propst and Hobbs 2000), with <br />about 60% collected from backwaters, 15% from pools, and 13% from pocket water (Converse and <br />Holden 1999). The YOY appeared to favor larger, deeper backwater habitats, and these habitats were <br />often associated with the mouths of secondary channels (Trammell and Archer 2000). This information <br />showed that in the San Juan River, similar to other rivers, Y OY predominately used backwaters, but other <br />low-velocity habitats were also used. <br /> <br />Although wild YOY Colorado pikeminnow were predominately found in the lower few miles of the San <br />Juan River, the hatchery-reared YOY remained throughout the river and some moved downstream with <br />storm-generated flow events (Trammell and Archer 2000). In 1997, 30 stocked YOY Colorado <br />pikeminnow were collected up to 8 miles above the Shiprock, New Mexico, stocking site about 1 month <br />after stocking (propst and Hobbs 2000), indicating upstream as well as downstream movement. Few <br />stocked YOY were found in the canyon sections below and above Mexican Hat, Utah, but they were <br />found in the low-gradient reach in the lower 13 miles of the river near the interface with Lake Powell. <br />Retention of fish stocked at Shiprock, New Mexico, was highest in the upper river. <br /> <br />3-8 <br /> <br />Program Evaluation Report <br /> <br />September 2000 <br />