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, . River (Valdez, et al., 1992). Historically, Colorado squawfish have been reported as far upstream as Paradox Valley as recently as 1962. Several other collections of squawfish have been reported from the Dolores River in the 1950's and 1960's. However, two surveys conducted in the 1970's and early 1980's of the Dolores River did not encounter this species (Valdez, et al., 1992) . Prior to the construction of McPhee Dam, extreme seasonal dewatering due to irrigation diversions (primarily the Montezuma Valley Irrigation Company Diversion near Dolores, Colorado) coupled with poor water quality conditions could have restricted the use of the Dolores River by Colorado squawfish. Operation of a uranium mill processing plant near the San Miquel River at Uravan, Colorado from the mid 1940's through the early 1970's is known to have resulted in several toxic spills into the river. Valdez, et al., 1992 also report a uranium concentrating plant was operational near Slick Rock; Colorado over generally the same time frame. Perhaps the most adverse limitation to aquatic life in the Dolores River may occur through Paradox Valley, Colorado, where water quality is severely degraded by the natural inflow of brine ground water. A fishery study conducted by Biowest Inc. in 1991-92, encompassed the section of the Dolores River from Bradfield Bridge (about twelve miles downstream of McPhee Dam) to the confluence of the Colorado River (Valdez, et al., 1992). During the course of this study, four Colorado squawfish were captured from the Dolores River, all within 2 kilometers of the Colorado River. It is not known if these fish were temporarily using the Dolores River or were permanent residents; however, since all of the squawfish collected were in such close proximity to the Colorado River, it is probable they were only temporarily inhabiting the Dolores River. Colorado squawfish are known to occur in the Colorado River downstream of its' confluence with the Dolores River; however, the small magnitude in flow change in the Colorado River associated with any of the alternatives would not adversely impact this species. All pool management alternatives would be beneficial compared to the No Action Alternative since the chronic 20 cfs flow during dry years would be avoided_ Lower flows associated with all pool management alternatives would occur during the winter, but based on studies conducted over the last three years, flow is not expected to be'dropped below 30 cfs during this period. The highest flow would be provided downstream of the dam during summer months. If a sufficient volume of water was available, flow no less than 70 cfs would be provided during the hottest summer periods. A 20 cfs flow was considered by Valdez, et al., (1992) as being extremely detrimental to aquatic life. They concluded; however, if sufficient flows were present, the Dolores River would have suitable habitat for reintroduction of experimental populations of Colorado squawfish. It is not known what magnitude of flow would be needed at this time. The Service has no immediate plans for reintroducing an experimental population of Colorado squawfish in to the Dolores River in the near future (pers. comm. John Hamil, USFWS, 1994). Reclamation does not believe that any of the pool management alternatives discussed above would affect either the Colorado squawfish or its' proposed critical habitat in the Colorado River. RAZORBACK SUCKER, BONYTAIL CHUB, HuMPBACK CHUB The razorback sucker, bony tail chub and the humpback chub have all been' reported from the Colorado River downstream of its' confluence with the Dolores River. None of these species have ever been reported from the Dolores River. As concluded above for the Colorado squawfish, Reclamation does not believe implementation of any of the proposed alternatives would directly affect either the species or their proposed critical habitat in the Colorado River. 13