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charge of the project was to survey the fishes of the San Juan Sub-basin in Colorado, Utah, and New Mexico, with particular emphasis on endangered and threatened species. During the course of the survey, Sublette took four roundtail chub at two locations but did not collect any of the other target species. This contrast to Olson's (1962) work 15 years earlier was alarming, but Sublette (1977) noted that the absence of these species in his collections did not preclude their occurrence in the study area. He called for a more intensive sampling effort when water levels were lower and water clarity was higher and stressed the need for electrofishing equipment to adequately sample the preferred habitat for adults of these species. In recent years, most of the ichthyofaunal studies of-the r - endangered Colorado River Basin fishes have concentrated on the Upper Mainstem Colorado and Green sub-basins. The San Juan Sub- basin has not been emphasized because it was thought that, even though the Colorado squawfish and Gila species were known historically to occur in the region, that they were now very rare or absent there. These presumed declines (Sublette 1977) were associated with the changes in habitat brought about with the closure of Navajo Dam. In 1987, the U.S. Bureau of Reclamation (USBR), funded the present study to determine the presence of protected or rare fishes in the New Mexico portion of the San Juan River. The purposes of this investigation as outlined in the study plan (U.S. Bureau of Reclamation 1987) were: 6