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f~ Lei General Description , The Colorado squawfish is an elongated pike-like fish. The mouth is large and nearly horizontal, with a pharyngeal tooth formula of 2,5-4,2; the long, ' slender pharyngeal teeth are adapted for grasping and holding prey. The anal and dorsal fin each have nine principal rays and the dorsal fin originates slightly posterior to the insertion of the pelvic fins. The scales are-small and embedded on the belly, breast, and nape, and number 80-95 in the lateral line. Adults are strongly countershaded with a dark, olivaceous back; lighter sides; and a white belly. Young are silvery and usually have a dark, wedge- shaped spot at the base of the caudal fin. Distribution and Abundance Historic Distribution The Colorado squawfish is endemic to the Colorado River basin. Early records indicate it was abundant in the mainstem Colorado River, most of its major ' tributaries, and in the Colorado River delta in Mexico (Jordan and Evermann 1896) (Figure 1). Colorado squawfish have been reported at the following locations: 1. Arizona: Gila River and its tributaries, the San Pedro, Salt, and Verde Rivers; the Colorado River mainstem from the United States-Mexico border to the Utah-Arizona State line and the lover most Little Colorado River ' (Minckley 1973, 1985). 2. California: Colorado River mainstem from the United States-Mexico border to the Nevada State line and the Salton Sea, which was sporadically filled with water from the Colorado River (Minckley 1973, 1985; Moyle 1976). 3. Colorado: Colorado River and lower reaches of the Gunnison, White, Yampa, Little Snake, Dolores, San Juan, Uncompahgre, and Animas Rivers (Jordan 1891; Ellis 1914; Beckman 1952; Lemons 1954; Johnson 1976; Valdez et al. 1982a), and Plateau Creek, a tributary of the Dolores River (Bob Burdick, ' U.S. Fish and Wildlife Service, pers. comm. 1990.). 4. Nevada: Colorado River mainstem (La Rivers 1962). 5. New Mexico: San Juan and Animas Rivers (Koster 1957, 1960; Platania 1990}. 6. Utah: Colorado, Green, Duchesne, San Juan, White,. and Dolores Rivers, and probably numerous smaller streams (Ellis 1914; Holden 1973; Seethaler 1978). 7. Wyoming: Green River mainstem (Baxter and Simon 1970; Bosley 1960; Johnson and Oberholtzer 1987) and Little Snake River (Marsh et al. 1991). ' 8. Mexico: Mainstem Colorado River and its tributaries and sloughs from the United States-Mexico border to the Gulf of California (Sonora and Baja California del Norte) (Follett 1961; Minckley 1979). ~ z