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~~~ ~ 4. ~, ~r ti i f! `ass ~;~.`.£:a ,/ 30 of the~15-mile reach, to contain 66.8 percent of the total habitat of the 15-mile reach; the whole river is habitat used to some degree. Also, there is no information to support an assumption that the four study sites contain significantly greater proportions of preferred habitats. The squawfish which were radiotelemetered by the Service were not captured randomly; capture _ efforts were concentrated in the four study sites because, in the past, relatively more squawfish had been caught in these areas than in other areas of the 15-mile reach. Although more squawfish "seem" to select the habitats L,~~` thin the four study sites than other habitats of the same types elsewhere in I~~ e reach, the reason for this is not known. Possible explanations include ''~" better juxta osition of habitat t es reater habitat complexity, water ~ quality, andpother factors. Without more specific habitat information on the ~, 15-mile reach outside of the four study sites, the habitat area changes caused ._,p~by the Project would be best estimated by assuming a linear relationship ~`'~, between habitat areas in the four study sites and in tie entire~l5-`mile reac . ~, / Biological Environment mac- ~` ~ ~3 ~~ The modification of flow regimes, water temperatures, sediment levels, and other habitat conditions caused by water depletions has contributed to the establishment of nonnative fishes. To the extent that it would reduce flows and contribute to further habitat alteration, the Project would contribute to an increase in nonnative fish populations. Endangered fishes would experience increased competition and predation as a result. Summary The proposed Project would reduce the amount of water delivered to critical habitat, alter the hydrologic regime, and degrade water quality by reducing dilution. Without actions taken to offset impacts, further flow reductions in the Colorado River are likely to jeopardize the continued existence of the endangered fishes and adversely modify or destroy their critical habitat. The Colorado River is an essential component of the habitat of the endangered fishes in the Colorado River Basin and is important in ensuring survival of these species a even p pu ations are lost in other subbasins as a result of catastr is events such as oil spills. ~ ~~ r REA ABLE AND PRUDENT ALTERNATIVE -o~,~~~'~egulations (50 CFR 402.02) implementing section 7 of the Act define d~" reasonable and prudent alternatives as alternative actions, identified during ~ ls~~` formal consultation, that: (1) can be implemented in a manner consistent with ~,,) ~,,.~ the intended purposes of the action; (2) can be implemented consistent with ~~,(~ the scope of the action agency's legal authority and jurisdiction; (3) are economically and technologically feasible; and (4) would, the Service believes, avoid the likelihood of jeopardizing the continued existence of listed species or resulting in the destruction or adverse modification of critical habitat.