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. . Attachment 1 APPENDIX 6.3 UPPER COLORADO RIVER BASIN RARE FISHES RIVER REACH PRIORI1IZA110N Table 6-3.1 provides a river reach prioritization of the Green and Colorado subbasins for the four rare Colorado River fishes. Table 6-3.2 provides a time-of-year and river mile comparison for each life stage of the four fish by river reach. This information was developed by the Upper Colorado River Basin Biological Subcommittee. Priorities were establ ished largely from information presented in the "Rare and Endangered Colorado River Fishes Sensitive Areas" d?cument (September 1984), prepared ~y the Upper Basin Biological Subcommittee. R1Ver reaches used by these rare fishes were ranked from I (highest priority) to 3 (lowest) according to their recognized importance for each species. The corresponding time periods when they are most important is noted. Important reaches for the bonyta i1 and Colorado squawfi sh mi grat i on corri dors were handled as special cases because they did not fit into the general format; migration routes for the razorback sucker, bony tail chub, or humpback chub remain to be delineated. River reaches identified in these special cases are considered to be among the highest priority tasks. Historic, unoccupied habitats were not listed but are considered important for research, and to the eventual recovery of these fishes. 1he controlled stocking and monitoring of presently uninhabited reaches can offer insight into habitat use, interspecific relationships, etc. For example, the recovery plan for the squawfish identi fies "primary habitats" that have been cut off from the remainder of the ecosystem (e.g., White River above Taylor Draw Dam), but are considered important to recovery. The Subcommittee emphasizes that each life stage of a species is critical and a habitat continuum must be present between each life stage if the species is to survive. Priorities are not implied nor should any be assumed either within or between species for the same ranking. Likewise, because of the uniqueness of each subbasin, the Subcommittee believes it is not proper to weigh priorities in one subbasin against priorities of the other subbasin. 1he Subcommittee strongly recommends against taking this approach. River reaches ranked as priority I or 2 are considered essential to species conservation; however, conclusions .should not be reached that areas of lower ranking may be less critical to species recovery. This information is intended to provide the reader with an analysis based on current information of important river reaches so decisions can be made to initiate recovery actions. As additional data are gathered, new high-priority areas may be identified and old ones refined. Incorporation of new data may require periodic adjustment or refinement in river management. At this time, the "Rare and document requires review. discriminating criteria and similar, annual review would Endangered Colorado River Fishes Sensitive Areas" New data will allow the application of more for refinement of the research 1 i st. Perhaps a be appropriate. 6-17