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<br />Icvee removal site. <br /> <br />Nonnative versus Native Fish Enhancement. Emphasis is placed on the determnation of absolute <br />and relative abundance changes of native and nonnative fishes as well as the interactions between <br />native and nonnative species. Past and ongoing research ( Tyus and Karp 1991, Crowl and <br />Lentsch 1995) suggest that many nonnative species now present in the Colorado River System <br />potentially limit native fish survivorship and recruitment through competition and/or predation. <br />Channel catfish, northern pike, green sunfish and small mouth bass. all pose significant threats as <br />predators of native species. Green sunfish, smallmouth bass and northern pike are known to <br />inhabit littoral or lentic habitats in midwestern lakes and reservoirs; thus, the effects of <br />development and management of floodplain wetlands must be assessed for nonnative as well as <br />native fish species. <br /> <br />First, we must determine which nonnative predators will use floodplain wetlands and whether <br />increased spatial complexity provided by aquatic macrophytes (and the ewected increase in yay <br />survivorship) will offset potential losses of native species due to nonnative predation. Second, we <br />must determine if additionallentic habitat will result in a differential, long-term increase in the <br />nonnative fish abundance due to increased spawning, growth and/or survivorship. <br /> <br />Iffloodpiain enhancement results in a significant increase in impurtant nonnative predators (e.g., <br />green sunfish, small mouth bass, etc.) in the river system, we expect long-term decreases in native <br />fish populations due to increased predation. It is highly pla!.lsible we will see a short-term <br />enhancement uf native fishes, followed by a.long-term increase in nonnative fishes resulting in an <br />overall, long-term decrease in the target native species. These 'hgged-iime' predator effects are <br />commonly observed and are well documented in 'invasion ecology' literature. <br /> <br />Prioritization. Selection and Wcl\ Defined PIa" for Site Develooment, Site prioritization and <br />scheduling has been a pervading issue in the habitat enhancement program. This strategy <br />identifies and prioritizes sites of highest importance for restoration through a randomized block <br />analysis design described in detail below. It should be noted that while we have provided a matrix <br />of the most feasible sites with respect to our overall design, we should take advantage of the <br />existing hydraulic models and data available to determine the feasibility of inundating various sites <br />(J. O'Brien, pers. comm.). Such endeavors are generally covered in the 'hydrology' section of <br />Floodplain Restoration documents. <br /> <br />6 <br />