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r-, <br />other native or introduced fishes. However, uncertainty still remains among <br />investigators as to the habitat needs of the razorback, particularly in light of <br />nonnative introductions (Minckley 1991 and Appendix A). <br />Evolutionary process and flood pulse adaptation related to razorback <br />sucker spawning site selection <br />Basin-wide examination of historical patterns of adult razorback <br />spawning concentration and associated geomorphic features can be used to infer <br />relationships between unconfined floodplain reaches and razorback reproduction <br />and recruitment. All known historic spawning aggregations in the Upper Basin <br />were located upstream from unconfined river reaches (Delta on the Gunnison; <br />Rifle, Grand Valley, and Moab on the Colorado River; and Rainbow Park, <br />Jensen and Ouray on the Green River). This suggests that survival of young <br />was greatest from spawning sites above unconfined river reaches. Unconfined <br />river reaches on the Colorado River system are associated with wetlands and <br />floodplains potentially rich in food resources for both young and adult fish. It <br />appears logical that the razorback sucker spawning strategy is correlated <br />strongly, not only in location but in timing, with the flood pulse. A geological <br />setting that provides a combination of cobble spawning sites, located upstream <br />from productive floodplain nursery areas, with a favorable flow regime to <br />maintain them, is required for recruitment success. <br />This flood pulse spawning strategy has been reported for fishes of both <br />tropical and temperate regions (Junk et al. 1989). The flood pulse and <br />floodplain connectivity are essential components of healthy alluvial river <br />ecosystems (Bayley 1991; Petts and Maddock 1994). The river continuum <br />concept is often used to assist our understanding of trophic food production and <br />nutrient cycling in a longitudinal direction and is considered an important <br />process of healthy river systems (Vannote et al. 1980). What is often ignored, <br />however, are the lateral contributions to river productivity provided by regular <br />?? 11