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<br />C) <br />C'"' <br />. . <br />..... <br />CD <br />(,J <br />c; <br /> <br />large endangered fishes (Colorado pikeminnow, razorback sucker, bonytaiI [Gila elegans], and humpback <br />chub [Gila cyphaJ) in the Colorado River Basin (Valdez et al. 2000a). Recovery goals include both <br />downIisting and delisting criteria, These goals wilI likely include preservation and enhancement of San Juan <br />River populations of Colorado pikeminnow and razorback sucker as important for recovery and may <br />provide guidelines for a demographically and genetically viable population. Therefore, intetim management <br />objectives are being developed for the San Juan River, but the temporary nature of these objectives should <br />be stressed. As such, the objectives will provide a target, but actual, sustainable populations that would <br />contribute toward recovery of the species may be considerably different. Also, the USFWS recovery goals <br />study may also provide recovery goals for the San Juan River, making interim population objectives <br />unnecessary. <br /> <br />IDENTIFY, PROTECT, AND RESTORE HABITATS WITHIN THE <br />SAN JUAN RIVER BASIN NECESSARY FOR RECOVERY OF THE <br />ENDANGERED FISH SPECIES AND MANAGEMENT OF THE <br />NATIVE FISH COMMUNITY <br /> <br />The 7-year research period studies met most of this objective, except for the identification of key habitats <br />for larval Colorado pikeminnowand razorback sucker, and perhaps key habitats for roundtail chub, The <br />primary accomplisInnent was detennining that mimicry of a natural hydrograph would create, maintain, and <br />maximize key habitats, and that it could be accomplished below the mouth of the Animas River through <br />reoperating Navajo Dam. The flow recommendations (Holden 1999) were the primary SJRIP undertaking <br />that addressed this objective directly, and the Flo w Report is the primary source of information conceming <br />the research and management actions taken to meet this objective, <br /> <br />The SJRIP studies showed that, to maximize key habitats for native fishes, flows in the study area below <br />the mouth of the Animas River needed to more-closely match a natural hydrograph in magnitude, duration, <br />and timing than they had since Navajo Dam's completion, High spring flows were a natural San Juan River <br />characteristic, an attribute that most fishes evolved with, a characteristic that is needed to create and <br />maintain key habitats for the endangered and native species. The life histories of the endangered species, <br />especially, are closely tied to the magnitude, duration, and timing of the natural hydrograph. Habitat for <br />spawning and rearing young, although very different for the two species, is improved and maximized with <br />a relatively natural annual hydrograph. To meet this need, the flow recommendations provided increased <br />spring peak magnitude and duration, while maintaining timing more similar to pre-dam conditions than to <br />post-dam flows. Base flows were also altered to resemble the magnitude and timing of pre-dam conditions, <br />These studies also suggested that changes in river temperature resulting from cold, hypolinmetic Navajo <br />Dam releases may be a limiting factor below, as well as above, the mouth of the Animas River and that this <br />area needs further study, <br /> <br />September 2000 <br /> <br />4-2 <br /> <br />Program Evalua1ion Report <br />