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common vernacular, razorback sucker. The ventral mouth is <br />moderate-sized with a cleft lower lip, lateral margins of the <br />lips are continuous and rounded. Head is elongate, with a <br />somewhat flattened dorsal surface and a well developed <br />fontanelle. Primary dorsal fin rays are usually 14-15 (12-17), <br />primary anal fin rays 7, total vertebrae 45-47, scales in lateral <br />series 68-87, and gill rakers 44-50 (1st arch). Body coloration <br />is dark brown to olivacious on upper dorso-lateral surfaces and <br />yellow to white on lower ventro-lateral surfaces. Adults grow to <br />a total length (TL) of 1 m and weigh 5-6 kg but are more commonly <br />400-700 mm TL and less than 3 kg (McAda and Wydoski 1980, <br />Minckley 1983). <br />Razorback suckers exhibit sexual dimorphism. Breeding males <br />are dark dorsally and bright yellow and orange laterally and <br />ventrally. Breeding females are less strongly colored. <br />Tuberculation associated with breeding condition is more <br />pronounced in males, especially on the anal and caudal fins, and <br />on the ventral surface of the caudal peduncle. Pelvic and anal <br />fin lengths are generally longer in males than in females, <br />whereas the reverse was true for length of the urogenital <br />papillae. Females are generally longer. and heavier than males <br />(McAda and Wydoski 1980, Minckley 1983, Meyer and Moretti 1988), <br />and may exhibit a low, broad, dorsal keel similar to that <br />described for some hybrid razorback sucker specimens (Minckley et <br />al. in press). More details describing sexual dimorphism can be <br />found in Minckley (1983). <br />5 <br />