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<br />002771 <br /> <br />the Genetics Management Guidelines, and the status of broodstock development for each of the four <br />endangered fishes <br /> <br />3.2.1 Endangered Fish Stocks in the Upper Colorado River Basin <br /> <br />Within the Upper Colorado River Basin, the various presumptive genetic stocks of each species <br />govern the development of brood stocks. A stock is identified as a randomly breeding group of <br />individuals that has spatial, temporal, and behavioral integrity from other randomly breeding groups <br />of that same species. In the Upper Colorado River Basin, eleven presumptive endangered fish stocks <br />appear to be based on definite spawning aggregations as shown in Table 3.2-1. <br /> <br />Table 3.2-1. Presumptive endangered fish genetic stocks in the Upper Colorado River Basin <br /> <br />Species Presumptive stocks <br />Razorback sucker L Green River <br /> 2. Colorado River <br />Bony/ail chub -0- Upper Basin <br />Humpback chub L Yampa River <br /> 2. Desolation-Gray Canyons <br /> 3. Black Rocks Canyon <br /> 4. Westwater Canyon <br /> 5. Cataract Canyon <br />Colorado squawjish L Yampa River <br /> 2. Desolation-Gray Canyons <br /> 3. Gunnison River <br /> 4. Upper Colorado River <br /> <br />Bonytail chub are nearly extirpated in the Upper Basin; only occasional individuals are captured very <br />infrequently.. Therefore, the probability of obtaining sufficient adult bonytails for broodstock <br />development is very remote. While the remaining bonytail in the Upper Basin is listed as a stock, a <br />definite stock has not been identified to date. In reality, bonytail in the Upper Basin should not be <br />considered a stock since they are extremely rare (Czapla 1997). Bonytail chubs of Lake Mohave <br />origin will be used to develop brood stocks for recovery efforts in the Upper Basin. <br /> <br />The humpback chub stocks in Desolation-Gray Canyons of the Green River and Cataract Canyons <br />of the Colorado River are in question because they appear to be hybrids with roundtail chubs based <br />on morphological analyses (McElroy and Douglas 1995). If these two stocks are deleted from the <br />eleven because they are hybrids, nine endangered fish stocks occur in the Upper Basin. Final <br />determination will depend on results of the genetics studies. <br /> <br />II <br />