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<br />OOu592 <br /> <br />gravel-pit ponds would be suitable for reconnection with the rivers. Many <br />of the gravel pits are deep -- below the deepest parts of the rivers. Such <br />ponds may allow nonnative fish species to flourish that would be <br />counterproductive to recovery of the endangered fishes. <br /> <br />By connecting select floodplain ponds with the river, embayments would be <br />created that could control reproduction of nonnative fishes while, at the <br />same time, they would likely benefit the endangered species. The declining <br />numbers of the endangered Colorado River fishes is attributed to the lack <br />of recruitment due to low survival from predation and competition by <br />nonnative fishes and possibly starvation during the critical early life <br />stages. It is believed that the high zooplankton productivity would <br />increase survival in the critical early 1 ife stages of the endangered <br />fishes. Zooplankton densities must be adequate to realize survival of <br />1 arva 1 endangered fi shes based on studi es of razorback suckers by Papoul i as <br />and Minckley (1990). At the same time, nonnative fishes would not be given <br />the opportunity to multiply in the floodplain ponds since they would enter <br />the river as the high spring streamflows subside. Earlier in this <br />Envi ronmenta 1 Assessment, it was stated that the target nonnative fi sh <br />species for control in floodplain ponds are centrachids, primarily <br />largemouth bass and green sunfish (Martinez and Nesler 1996). Centrarchid <br />species do not fare well in the riverine environment based on monitoring of <br />fish populations by the Recovery Program (McAda et ale 1994 a,b; 1995). <br /> <br />This alternative would be applicable to either natural floodplain <br />depress ions or gravel-pit ponds in the fl oodp 1 a ins of the Colorado and <br />Gunnison rivers that connect with the river on a frequent basis. Mitchell <br />(1995) stated that about 60% of the floodplain ponds, included in his <br />inventory, connected with the ri vers either annually or one out of ten <br />years. Reconnect i on of these ponds with the ri vers woul d all ow the <br />product i ve off -channe 1 habitats to connect with the ri vers annually, <br />producing zooplankton that are needed by the early life stages of the <br />endangered fishes. <br /> <br />Burdi ck (1994) developed a conceptual management pl an to experimentally test <br />the assumptions that were described in the above paragraphs. In the Fall <br />of 1996, a gravel-pit pond (29 5/8 Road pond) along the Colorado River near <br />Grand Junction was re-connected with the river. The fish populations using <br />this manmade "embayment" are currently being monitored by the Colorado River <br />Fi shery Project of the U. S. Fi sh and Wil dl i fe Servi ce in Grand Junction, <br />Colorado. This experimental study will provide insight into the use by <br />nat i ve fi shes, i nc 1 ud i ng endangered fi shes, and nonnative fi shes. The <br />results of this experimental field study will be used for decisions on re- <br />connect i ng other fl oodp 1 a in ponds with the ri ver and how to best manage such <br />manmade "embayments" in the future. <br /> <br />Obviously, this alternative has potential for endangered fish recovery in <br />some of the floodplain ponds but not all. Therefore, it would be premature <br />to re-connect a large number of ponds with the rivers until the response of <br />both native and nonnative fishes is better understood. <br /> <br />23 <br />