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The Colorado pikeminnow is the largest cyprinid fish (minnow family)native to North America <br /> and evolved as the main predator in the Colorado River system. Individuals begin consuming <br /> other fish for food at an early age and rarely eat anything else. It is a long, slender, cylindrical <br /> fish with silvery sides, greenish back, and creamy white belly (Sigler and Sigler 1996). <br /> Historically, individuals may have grown as large as 6 feet(ft) long and weighed up to 100 <br /> pounds (estimates based on skeletal remains) (Sigler and Miller 1963), but today individuals <br /> rarely exceed 3 ft or weigh more than 18 pounds (lbs) (Osmundson et al. 1997). <br /> The species is endemic to the Colorado River Basin,where it was once widespread and abundant <br /> in warm-water rivers and tributaries from Wyoming,Utah,New Mexico, and Colorado <br /> downstream to Arizona,Nevada, and California. Currently,wild populations of pikeminnow <br /> occur only in the Upper Colorado River Basin (above Lake Powell) and the species occupies <br /> only 25 percent of its historic range-wide habitat(Service 2002b). Colorado pikeminnow are <br /> long distance migrators, moving hundreds of miles to and from spawning areas, and requiring <br /> long sections of river with unimpeded passage. They are adapted to desert river hydrology <br /> characterized by large spring peaks of snow-melt runoff and low,relatively stable base flows. <br /> The Office of Endangered Species first included the Colorado pikeminnow (as the Colorado <br /> squawfish) in the List of Endangered Species on March 11, 1967 (32 FR 4001). It is currently <br /> protected under the ESA as an endangered species throughout its range, except the Salt and <br /> Verde River drainages in Arizona. The Service finalized the latest recovery plan for the species <br /> in 2002 (Service 2002b),but is currently drafting an updated revision. <br /> The Service designated six reaches of the Colorado River System as critical habitat for the <br /> Colorado pikeminnow on March 21, 1994 (59 FR 13374). These reaches total 1,148 miles (mi) <br /> as measured along the center line of each reach. Designated critical habitat makes up about 29 <br /> percent of the species' historic range and occurs exclusively in the Upper Colorado River Basin. <br /> Portions of the Colorado, Gunnison, Green,Yampa, White, and San Juan Rivers are designated <br /> critical habitat. The primary constituent elements of the critical habitat are water,physical <br /> habitat, and the biological environment(59 FR 13374). <br /> Water includes a quantity of water of sufficient quality delivered to a specific location in <br /> accordance with a hydrologic regime required for the species. The physical habitat includes <br /> areas of the Colorado River system that are inhabited or potentially habitable for use in spawning <br /> and feeding, as a nursery, or serve as corridors between these areas. This includes oxbows, <br /> backwaters, and other areas in the 100-year floodplain that provide access to spawning, nursery, <br /> feeding, and rearing habitats when inundated. The biological environment includes food supply, <br /> predation, and competition from other species. <br /> Recovery of Colorado pikeminnow in the Colorado River Basin is considered necessary only in <br /> the Upper Colorado River Basin (above Glen Canyon Dam, including the San Juan, and Green <br /> River subbasins)because of the present status of populations and because existing information <br /> on Colorado pikeminnow biology support application of the metapopulation concept to extant <br /> populations (Service 2002b). As a result, this BO will focus on the status of the Colorado <br /> pikeminnow in that unit. <br /> 6 <br />