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<br />APPENDIX A <br />BACKGROUND MATERIAL ON THE ENDANGERED FISHES <br /> <br />The two endangered fish species considered in this EA, the Colorado squawfish and razorback <br />sucker, are known to be highly or moderately migratory (Tyus and McAda 1984; Tyus 1987; <br />Tyus 1990; Tyus 1991), The construction of dams in the Upper Colorado River Basin present <br />barriers to the natural migration tendencies of these two fishes (Burdick and Kaeding 1990; U.S, <br />Bureau of Reclamation and U.S. Fish and Wildlife SelVice 1995), <br /> <br />The Colorado squawfish can be termed a highly migratory species while the razorback sucker is a <br />moderately migratory species, based on tagging studies (Tyus 1985, 1986; Tyus and Karp 1990; <br />Mickey et al. 1993; Wick et al. 1982), Movement and use of habitat varies by life stage (age) for <br />both species and various habitats appear to be important to sUlVival in their life history. Recovery <br />of the fish involves the development of self-sustaining populations through natural reproduction; <br />therefore, recovery efforts must consider all aspects of the life history and habitat requirements if <br />development of self-sustaining populations is to be realized. <br /> <br />Presently, the Colorado squawfish is absent from its historic range in the river from the Price- <br />Stubb Dam upstream to Rifle, and razorback suckers are extremely rare upstream from Palisade, <br /> <br />Colorado squawfish lalVae (when fish emerge from eggs, they are termed lalVae) drift <br />downstream from spawning areas, perhaps over 90 miles or more and this may selVe as a way to <br />disperse young into suitable backwater areas (Haynes et at. 1984; Nesler et at. 1988; Tyus and <br />Haines 1991). As the lalVae grow to a larger size, they move upstream to establish a "home area" <br />used for feeding and resting during most of the year (Tyus 1991). Adult squawfish exhibit a high <br />fidelity to return to specific spawning sites but migrate back to a "home area" for feeding after <br />spawning (Tyus 1985,1990; Tyus and McAda 1984), <br /> <br />LalVal squawfish drift downstream from spawning areas and occupy warm, shallow, backwaters <br />as they become larger (Tyus 1991), Small juveniles remain in backwater areas and larger <br />juveniles or subadults move upstream to occupy the mainstem and major tributaries as feeding and <br />resting areas that may be a long distance from spawning sites (Tyus and Karp 1989). The <br />squawfish is considered a "large river" fish that inhabits the mainstem of the Colorado and Green <br />Rivers and major tributaries such as the Gunnison, White and Yampa Rivers. Y oung-of-the-year <br />and juveniles were generally captured in backwaters that were 3 feet or less in depth over silt or <br />sand substrates, with low water velocities (Twedt and Holden 1980). Haynes et at. (1984) <br />reported that young squawfish occupy areas where water velocity is less than 0.1 feet per second, <br />Adult squawfish occupied habitats with sand, gravel, or cobble substrates with water velocities of <br />0,08 to 0,39 feet per second (Twedt and Holden 1980). Adults occupy pool and eddy habitats <br />along the river shoreline with a medium depth (3 to 6 feet) during pre- and post-runoff periods, <br />During periods of high flow, adults prefer backWater areas and the flooded mouths of tributaries. <br />Spawning fish use specific cobble bars in runs to deposit their eggs but return to resting-staging- <br />feeding areas in pools and eddies in other parts of the basin (Tyus 1990). <br /> <br />A-l <br />