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G-f' Gardner Pond. adjacent to the Colorado River (river mile 174.4) located at 29-5/8 Road, is a pond that was connected to the mainstem river in December 1995. The pond presently holds water year-round and does not drain naturally. A report discussing the seasonal use of these two ponds by endangered and other native fishes as well as nonnative fishes is currently being prepared (Burdick et al. IN PREP). An earthen berm was placed in the connection channel in late-1996 to prevent nonnative fish in the pond from escaping into the river. The pond was drained and most nonnative fish were removed in mid-March 1997. Plans now are to back-fill and slope (e.g., 8:1 slope) toward the river to allow seasonal flooding and draining. and finally reconnect the sloped pond to the river. Gravel pits in the floodplain isolated from the mainstem river could be connected to the river to create ephemeral habitats for native fishes rather than perennial habitats that are favored by nonnative fishes. Prior to being connected to the river, total eradication or removal of all nonnative fishes would be necessary. To .create ephemeral habitats, gravel pits would have to be back-filled and sloped toward the river to allow river water to seasonally fill the pond during spring runoff and drain following runoff. Reduce Nonnative Fish and Sportfish Impacts The native fishes of the Upper Colorado River Basin are declining in abundance. Significant anthropogenic changes to the physical habitat have undoubtedly played an important role in the decline of four of the "big river" fishes. but changes in the biological environment may also. have been equally significant. Physical changes in the riverine habitat have been accompanied by the introduction and proliferation of nonnative fishes, and concomitant declines in native fishes. At least 67 nonnative fishes have been introduced actively or passively into the Colorado River system during the last 100 years (Minckley 1982: Tyus et al. 1982: Carlson and Muth 1989; Minckley and Deacon 1991: Maddux et al, 1993). By 1980, more than 50 nonnative fishes had been actively introduced into rivers and reservoirs of the Colorado River basin (Minckley 19B2; Tyus et al. 19B2; Carlson and Muth 1989). Native big river fishes have disappeared from about three-fourths of their original habitat while introduced fishes have become more widespread and abundant. Recent studies have also documented a decline in the abundance of native fish species as nonnative species increased in abundance (Joseph et al. 1977: Behnke 1980: Osmundson and Kaeding 1989; Quarterone 1993). In some instances, drastic changes in the fish fauna have occurred in the Lower Colorado River (downstream of Glen Canyon Lf