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fishes. Selection of this option would be based on the assumption that endangered species can be recovered by implementing measures other than floodplain restoration. 2. Install additional levees/dikes to prevent use of floodplain habitats by nonnative fishes. This option assumes that, if nonnative fishes would use and/or benefit from restoration of floodplain habitats, then existing floodplain habitats should be "walled-off" to prevent their use by nonnatives. However, some nonnative fishes are also abundant in main-channel slackwater habitats. It is not feasible to "wall-off" all backwaters, embayments, and tributary mouths to prevent nonnatives from using or benefitting from those habitats. Such measures would result in a river that resembles a concrete-lined canal where the numbers of all fish species would be reduced. 3. Restore sites only in locations where there are no "problematic" nonnative fishes. All parts of the Upper Basin contain some "problematic" nonnative fish species. Some biologists believe that, wherever habitat is enhanced or restored, nonnative fishes will use them. The response of fishes to newly created habitats will vary among the various species, 4. Control access to (and from) restored sites by nonnative fishes There are two degrees of control for nonnative fishes: total and partial. Total control can be accomplished only if the habitat is totally isolated from the main channel of the river. In this case, the habitat (e.g., pond or hatchery) could be drained or poisoned to remove all fishes; then stocked with razorbacks for rearing. One means of partial control can be accomplished via inlet and outlet screens, which prevent access to the habitat by larger fishes, but permit access to early life stages of fishes. During high flow years, however, the screens, dikes, and levees can be breached or over-topped, allowing access to any or all species and sizes of fish. Another technique for partial control is to install an outlet control structure with a fish kettle. This allows draining the habitat back into the river through a screen, and harvesting all of the fishes, Nonnative fishes can then be removed from the kettle, thereby preventing them from getting into the river. A third approach for partial control involves restoring and managing floodplain habitats to behave naturally. Habitats would be allowed to flood and drain during spring flows, providing ephemeral floodplain habitats. Nonnative fishes may use the habitats for the relatively short period of time in which they are inundated, but they would not be 4