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H Heiden ,. LI jCfS'3 IL I I''i''/Id!:-C ' . "'IIJAb, / ~ 1; J~IV~.Y JJ7t J-)o / d Vvl 10~ ouglas Selby Univer.: ity of Nevada, Las vega.~/ All known aquatic system in the Tecopa area of so~eastern California were surveyed during the su er of 1977 in an effort locate new populations of the endangered Tecop pupfish (Cyprinodon nevad sis calidae). Many artificial and natural habit contain populations of C nevadensis which should be eva- luated by a camp' ent taxonomist. Perhaps ne of these populations could be a transplant of . n. calidae. Habitats we e also surveyed for basic water che- mistry, phys'cal description, and inver ebrate life. The information has been compiled i a report to California 0 artment of Fish and Game. S. tus and Preferred Habitat f the Rare Fishes of the Green River, Utah Paul B. Holden B /WEST, Inc., Logan, Utah I ABSTRACT \ Over 19,000 fish were collected by seines and electrofishing gear in August and September, 1977, in the Green River between Jensen and Green River, Utah. Adults and juveniles of all four rare fishes (Colorado squawfish, Ptychocheilus lucius, humpback chub, Gila cypha, bony tail chub, Gila elegans, and razorback sucker, Xyrauchen texa~were found. The collection of young-of-the-year razorback suckers is the first for the upper Colorado Basin. Young-of-the-year Colorado squawfish preferred backwaters with no current, a silt substrate and 1-2 feet of depth. Juvenile squawfish preferred bacKwaters with more than 1 foot of depth, but also used slow eddies. Subadult squawfish were primarily found in eddi es and runs. Young-of-the-year humpback chubs used backwaters and eddies with velocities of less than 0.5 fps, a preferred depth of 2 feet and a silt and sand substrate. Juvenile chubs used a wider range of microhabitat, but preferred velocities of less than 0.6 fps. Adult humpback chubs used a variety of habitats, velocities, substrate, and depths, with no clear preferen- ces. Young-of-the-year Colorado squawfish were fin clipped in one backwater to determine movement. Few marked fish were found, indicating movement, but the r-extent of the movement was not determined. Many introduced fishes were found \ in samples containing young rare fishes, indicating the possibility of com- i petition and/or predation. I L--- ~,.o~{~ ~~ ~ r,'JIY 1/9~i )