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<br />.. <br /> <br />I <br /> <br />OOQ5G3 <br /> <br />undoubtedly contributed to the demise of the endangered Colorado <br />River fishes. <br /> <br />Nonnative fishes compose 76% of the fish species (42 of 55 species) <br />in the riverine environment of the Upper Colorado River Basin (Tyus <br />et al. 1982). These nonnative fishes constitute most of the fish <br />numbers (96.7 - 99.6%) found in backwater habitats in the Upper <br />Basin (Cranney 1994; McAda et ale 1994a,b; 1995). Researchers and <br />other participants in the Recovery Program agree that predation and <br />competition by established, self-sustaining populations of <br />nonnative fishes and chronic escapement of nonnative fishes from <br />off-channel ponds and impoundments are factors that increase <br />mo rta 1 i ty of the enda nge red fi shes. They fu rthe r ag reed tha t <br />action to control nonnative fishes was needed immediately. <br /> <br />Recovery Program participants identified an urgent need to control <br />or manage nonnative fish species in the Upper Colorado River Basin <br />if recovery of the endangered fi shes was to be achi eved. They <br />participated in the development of a strategic plan to remove or <br />reduce existing populations of nonnative fish species from habitat <br />used by the endangered Colorado River fishes (Tyus and Saunders <br />1996). One of the highest priorities in the Recovery Program's <br />strategic plan for control of nonnative fishes is prevention of <br />chronic escapement of nonnative fish species from off-channel ponds <br />along the Upper Colorado and Gunnison rivers that could further <br />exacerbate existing interactions of nonnative fishes (i .e., <br />predation and competition) on the endangered fishes. <br /> <br />Recovery Program participants believe it is unlikely that the <br />endangered fishes will be recovered (i.e., establish viable, self- <br />sustaining populations through natural reproduction) until problems <br />associated with nonnative fishes are addressed. <br /> <br />The proposed action was to use mechanical fish control methods of <br />draining floodplain ponds and removing nonnative fish species or to <br />treat the ponds with powdered rotenone that is an excellent <br />pi sci ci de. The nonnati ve fi shes woul d be removed from <br />approximately 25 ponds annually and up to 150 ponds by the Year <br />2002. <br /> <br />The proposed action will decrease the chronic or periodic <br />escapement of nonnative fish species from floodplain ponds and <br /> <br />2 <br />