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<br />able to expand, as they do in permanent ponds and gravel pits. In some <br />instances (i.e., ponds filled by overbank flooding), fish that remain in <br />the habitats after the river subsides are stranded and their ultimate <br />fate is death unless the pond reconnects with the river before it dries <br />up. Some sites can contain water for several years while others dry up <br />through evaporation in the arid climate of the Upper Basin, <br /> <br />5. Manage nonnative fishes at locations, possibly throughout the Upper <br />Basin (via flow management, removal, etc.), where habitats are enhanced <br />or restored. <br /> <br />At specific locations, it may be possible to partially control some <br />species of non~ative fishes to some degree via mechanical removal <br />methods and/or chemical control methods such as spot-poisoning prior to <br />colonization by drifting razorback sucker larvae, Predators such as <br />northern pike, smallmouth bass, largemouth bass, and channel catfish may <br />be controlled through mechanical control methods. Partial control of <br />fish populations is a temporary measure because other undesirable (i.e., <br />nonnative) fishes will fill the void (Wiley and Wydoski 1993). In <br />addition, fishes exhibit compensatory growth and fecundity associated <br />with growth that allows a high degree of resilency in reduced fish <br />populations. <br /> <br />There are several nonnative fishes that may be more vulnerable to high <br />spring flows than native fishes (Muth and Nesler 1993). Valdez (1990) <br />documented that red shiner populations were reduced after high <br />streamflows but exhibited resilency whereby the population structure was <br />similar to before the high flow events in several years. Furthermore, <br />some of nonnative fish species may be adversely affected by the <br />turbidity associated with high flows. Nonnative minnows that are both <br />predators and competitors with the endangered fishes include the <br />abundant red shiner and fathead minnow (Gutermuth et al. 1994; Haines <br />and Tyus 1990; Muth and Snyder 1995). While predation of razorback <br />sucker by the red shiner is limited to gape size (Crowl 1994), fathead <br />minnows prey upon catostomid larvae through group attack and then feed <br />on the pieces so that gape size is not as critical (Dunsmoor 1993), <br /> <br />6. Use an experimental approach to enhance or restore floodplain habitats <br />by employing adaptive management. <br /> <br />Poor survival during the early life stages of the razorback sucker is <br />due in part to starvation since main channel habitats do not produce <br />sufficient zooplankton in the early spring when razorback suckers spawn, <br />Off-channel habitats in the Upper Basin have been shown to be extremely <br />productive for zooplankton (magnitudes higher than main channel or <br />backwater habitats). Therefore, enhancement or restoration of <br />floodplain habitats has been identified as an element in the Recovery <br />Program that would aid in getting razorback larvae through the critical <br />early life period, However, it is recognized that a number of nonnative <br />fishes will also benefit from enhancement or restoration of floodplain <br />habitats. By employing an adaptive management approach through field <br />experimentation, the bottleneck of recruitment for razorback sucker may <br /> <br />5 <br />