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1 ' Il~ITRODUCTION General Description ' The Colorado squawfish (Ptychocheilus lucius) is the largest of three living species of this genus, known through fossil records back to Pliocene time.° It is elongate, somewhat axnpressed dorsoventrally, ' with apike-like body and a long and flattened head. The mouth is large and nearly horizontal, and the pharyngeal teeth and arches are long and fragile, adapted for grasping prey (tooth formula 2,5-4,2). - the body, and origi- The dorsal fin has nine rays, lies well back on Hates behind the insertion of the pelvic fins. Scales are small and embedded on the belly, breast and nape, with 80-95 in the lateral ' line. Adults are strongly countershaded, with a dark, olivaceous back, lightening along the sides to a whitish belly. In the young, there"is a dark, wedge-shaped spot at the base of the caudal fin. Although the descriptive term lucius means."pike-like," the Colorado squawfish belongs to the large and diverse minnow family, Cyprinidae, ' and is considered to be the largest minnow in North America (Miller 1961). Maximum weight has been recorded as exceeding 80 lbs. (36 kg) and the length attained nearly 6 ft. (1.8 m); however, specimens over 15 lbs (7 kg) have been rare over the past ten years. Their huge size and upstream migratory habits won for them the vernacular "white salmon of the Colorado." Other members of this genus are restricted ~ the Sacramento-San Joarn,;n, 1 Columbia, and Umpqua and Siuslaw rivers, in northern California, Oregon, and Washington. The abundance and predatory food habits of these west coast relatives seem to have defamed the Colorado squawfish, as Everhart and Seaman (1971) indicated under the heading Colorado squaw- fish: "Because the squawfish are such predators on game fish, control has long been a fishery management problem. Everything frcan dy- namite to chemical control has been tried. The most recent de-- velopment is a specific chemical called 'Sciuoxin' for the control ' of these predators." ' There is little doubt about the predatory habits of squawfish; in fact, adult Colorado squawfish are fed trout in Willow Beach National Fish Hatchery (Toney 1974). Hower, no population control has ever been necessary-for Colorado squawfish, and in fact now just the opposite is necessary. The Endangered Species List published in the Federal ~ister on 11 March; 1967, (Vol. 32(48)c4001) included Colorado squawfish; full protection under the Endangered Species Act of 1973 came from the Fed- eral ister listing on 4 January, 1974 (Vol. 39(3): 1175). This ' Recovery Plan is being written to point out problems the remaining Colorado squawfish must overcar~e for continued existence and to develop a management scheme to assist their struggle for survival. ' 1