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study are the Colorado squawfish, species in the genus Gila (bonytail, humpback chub, and roundtail chub) and the razorback sucker. These five taxa comprise the target species, as defined in this report. Historic Collections Cope and Yarrow (1875) were the first to report on fish from the San Juan River drainage. Roundtail chub (previously identified as bonytail) were taken in the San Juan River, New Mexico, by Lt. R. Birnie in 1874 (Cope and Yarrow 1875). No additional details were provided and apparently no other species were taken from the drainage. Jordan (1891) provided a more thorough account of the fish fauna from the upper reaches of the San Juan River drainage. He described 10 systems (all in Colorado), three of which were sampled (Animas and Florida rivers and Leitner's Creek). Jordan (1891) collected four species (cutthroat trout, Oncorhynchus clarki, speckled dace, Rhinichthys osculus, bluehead sucker, Pantosteus discobolus, and mottled sculpin, Cottus bairdi) and conveyed second-hand reports of Colorado squawfish, flannelmouth sucker, Catostomus latipinnis, and razorback sucker ascending the Animas River to Durango, Colorado during spring. There are no specimens to substantiate these latter claims. Evermann and Rutter (1895) reviewed and summarized published reports on the fishes of the Colorado River basin but did not provide any new information on the San Juan River Sub-basin. Evermann and Rutter (1895) were erroneously credited with providing Colorado squawfish records for the San Juan River by VTN Consolidated, Inc. and Museum of Northern Arizona (1978), and Minckley and Carothers (1979). The next documented San Juan River drainage fish collection, at Aztec, New Mexico in 1934, did not contain any target species. However, two years later, on 4 July 1936, the presence of Colorado squawfish in the San Juan River was confirmed by the collection of three specimens approximately 32 river miles (52 km) upstream of the confluence of the San Juan and Colorado rivers at Alcove Canyon in San Juan County, Utah (University of Michigan Museum of Zoology [UMMZ] 211183). Additional Colorado squawfish (U.S. National Museum [USNM] 132091) and roundtail chub (USNM 118996) were collected from the San Juan River sometime prior to 1941 (specimens were catalogued into the USNM in 1941), but the date of collection and precise locality data did not accompany the specimens. Lemons (1955), while. conducting a channel catfish, Ictalurus punctatus, study for the Colorado Division of Wildlife, collected roundtail chub and a 5.4 kg (12 lb) Colorado squawfish in the San Juan River of Colorado near Four Corners.- This is the only documented report of Colorado squawfish from the San Juan River in Colorado. In 1959, two adult Colorado squawfish were collected near Rosa in Rio Arriba County, New Mexico (Koster 1960) thereby 3