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Genus Rhinichthys DACE There are two species of the genus Rhinichthys native to, and found in, Colorado. KEY TO THE GENUS RHINICHTHYS 1. a. A frenum is present, so that the premaxillaries are not protractile (there is no groove completely across the snout). The skin across top of head is continuous with the upper lip. LONGNOSE DACE Rhinichthys cataractae : LONGNOSE DACE Rhinichthys cataractae (Valenciennes) A streamlined, torpedo-shaped min- now; mouth inferior, overhung by snout, frenum present, small barbel hidden by a fold of skin at each corner of mouth; dor- sal fin with 8 rays; lateral line complete and nearly straight, peritoneum is silver with brown specks. Coloration of adults varies. The back is tan to brown, fading to white on the stomach with dark speckles often present on back and sides. Breeding-colored males have red-orange on the corners of mouth, cheeks, and fins. The longnose dace is much like the speckled dace (see next species account). The longnose dace is a small minnow seldom exceeding 3.5 inches. Range: The longnose dace is an ex- tremely widely distributed fish, ranging throughout most of Canada south to Washington, east to New York, and south again through the Appalachians to Ten- nessee, to the Rocky Mountains, and to Texas (Scott and Crossman 1973). In Col- orado, the species is native to the Arkan- sas River, Rio Grande, the Platte river system (Ellis 1914) and the Republican River (Cancalosi 1980). Propst (1982) found longnose dace in the transition zone streams of the South Platte as well as the mainstem river from the foothills to the Nebraska border, and in the North Platte drainage. Habitat: The species is usually found in riffle areas of streams that have a rub- ble or gravel substrate. In the eastern plains areas of the South Platte, riffle areas of sand and gravel provide adequate habitat. Young are restricted to areas of Longnose dace - frenum present. b. There is no frenum present so that premaxillaries are protractile (There is a groove across the snout). The skin across top of head is not con- tinuous with upper lip, a groove separates the two. SPECKLED DACE Rhinichthys osculus F Speckled dace - frenum absent. Family Cyprinidae -Genus Rhinichthys Adult longnose dace. I l I I ? I i - T i ` -- \?---? a --- 5 I I l _ rs-- I i As 1 I / , Distribution by County of the longnose dace. 23 Colorado's Little Fish