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.. o <:) o l" CJ1 en Mr. Calvin Joyner 11 shore of the San Juan arm of Lake Powell (Platania 1990; Platania et al, 1991). These fish were captured near a concrete boat ramp at Piute Farms Marina and were believed to be either a spawning aggregation or possibly a staging area used in preparation for migration to some other spawning site. Of the 12 individual razorbacks handled in 1987, 8 were running ripe males while the other 4 specimens were females that appeared 9ravid. In 1988, a total of 10 razorback suckers were handled at the same general location, 5 of which were in reproductive condition (Platania et al. 1991). Six of the 10 individual specimens in the 1988 samples were recaptures from 1987. Also, in 1988, a single adult tuberculate male razorback sucker was captured at approximately river mile 80 on the San Juan River near Bluff, Utah. Particularly noteworthy is that this is the first confirmed record of this species from the main stem San Juan River. The presence of this reproductively mature specimen suggests that the razorback may be attempting to spawn in some unknown location within the riverine portion of the San Juan drainage. No razorback suckers were captured in 1989. No larval specimens, nor any other size classes of razorbacks (other than adults), have ever been documented in the San Juan River drainage. The limited nature of historic and more recent icthyofaunal surveys of the San Juan River drainage do not allow for accurate quantitative estimates of relative abundance for any of its native fishes, including the razorback sucker, However, the existing scientific literature and historic accounts by local residents strongly suggests that razorback suckers were once a viable, reproducing member of the native fish community in the San Juan River dra i nage. Currently, the razorback sucker is rare throughout its historic range and extremely rare in the main stem San Juan River. A small enclave of razorback suckers persist in the San Juan arm inflow area of Lake Powell. Protection and enhancement of the San Juan River is needed to guard against the threat of extinction of this species in native riverine environments. By returning the San Juan River to a more natural condition, it is conceivable that riverine habitats important to the ecology of razorback suckers could be provided that would assist in the recovery of this unique native species. Critical Habitat Critical habitat has been designated within the 100-year floodplain of the razorback sucker's historical range in the following section of the San Juan River Basin (59 F.R, 13374). New Mexico. San Juan Countv: and Utah. San Juan Countv. The San Juan River from the Hogback Diversion in T. 29 N., R. 16 W., section 9 to the full pool elevation at the mouth of Neskahai Canyon on the San Juan arm of Lake Powell in T. 41 S., R. 11 E., section 26, BioloQV Specific information on biological and physical habitat requirements of the razorback sucker is very limited. Localized extirpation of razorback suckers