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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />(ATPase 8, 6, and ND2) to serve as our genetic marker. Preliminary results indicate three major <br />clades. The largest consists of the mainstem Colorado, Virgin, Sevier, Bill Williams, and upper <br />Little Colorado rivers. Relationships within this large clade are relatively unresolved, but three <br />distinct Virgin River haplotypes are diagnosed. Furthermore, mainstem Colorado populations are <br />undifferentiated from WY to southern Grand Canyon. The second large clade represents the Gila <br />River, and is quite distinct from the mainstem Colorado. The third clade, the Lahontan, is most <br />divergent of all. Management implications are discussed. <br /> <br />Mueller, G'., and P. Marsh2 <br /> <br />JU.S. Geological Survey; 2Arizona State University <br /> <br />Lost, a Desert River and Its Native Fishes: A historical perspective of the lower Colorado <br />River. The authors describe historical conditions ofthe lower Colorado River through old <br />photographs and records. Few people appreciate the magnitude of change that has occurred in <br />the lower basin, especially through the loss ofthe Colorado Delta. Before high dams and storage <br />reservoirs, the river periodically flooded hundreds of square kilometers of floodplain and desert <br />playa. W. L. Minckley once suggested the core populations of razorback sucker (Xyrauchen <br />texanus), bonytail (Gila elegans), and Colorado pikerninnow (Ptychocheilus lucius) emanated <br />from the broader floodplain and oxbow habitats, much of that being found in the delta. The <br />Colorado delta and lower 125 miles of river has been lost to upstream water diversions and to the <br />plow. The river that remains more closely resembles the upper Mississippi or Missouri rivers both <br />physically and biologically. Ecological conditions and biotic communities from which native fish <br />evolved have been totally lost. In fact, the lower Colorado River has the dubious distinction of <br />being among the few major rivers of the world with an entirely introduced fish fauna. Regardless, <br />both Federal and state agencies are reintroducing endangered fish into these waters. It should not <br />come to anyone's surprise these traditional approaches are proving ineffective. <br /> <br />Posters and Displays <br /> <br />Snyder, D.E. <br /> <br />Larval Fish Laboratory, Colorado State University, Ft. Collins, CO <br /> <br />Descriptive Species Account for Larval and Early Juvenile Longnose Sucker, Catostomus <br />catostomus. The current guide to larval and early juvenile suckers of the Upper Colorado River <br />Basin (UCRB; Snyder and Muth 1990) covers six of the seven species found in the basin. <br />Longnose sucker (Catostomus catostomus) was not included because of budgetary limitations and <br />the improbability of encountering its larvae or early juveniles in Recovery Program collections. <br />However, with the collection of a significant number of juvenile longnose sucker and many larvae <br />suspected to be longnose sucker or hybrids in the lower Gunnison River in 1993, confidence in <br />identification of those and other suckers was compromised, and the need to comparably describe <br />and incorporate the last of the UCRB suckers in the guide and key became evident. Accordingly, <br /> <br />19 <br />