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the food chain which could adversely affect the endangered fishes, particularly the <br />predatory Colorado pikeminnow. Selenium is of particular concern due to its effects on <br />fish reproduction and its tendency to concentrate in low velocity areas that are important <br />habitats for Colorado pikeminnow and razorback suckers. <br />The proposed project would affect the physical condition of habitat for the four listed fish <br />by resulting in a reduction of water. This reduction would contribute to the cumulative <br />reduction in high spring flows, which are essential for creating and maintaining complex <br />channel geomorphology and suitable spawning substrates, creating and providing access <br />to off-channel habitats, and possibly stimulating Colorado pikeminnow spawning <br />migrations. Adequate summer and winter flows are important for providing a sufficient <br />quantity of preferred habitats for a duration and at a frequency necessary to support all <br />life stages of viable populations of all endangered fishes. To the extent that the proposed <br />project will reduce flows, the ability of the river to provide these functions will be <br />reduced. This reduction of water affects habitat availability and habitat quality. <br />To the extent that it would reduce flows and contribute to further habitat alteration, the <br />proposed project would contribute to an increase in nonnative fish populations. The <br />modification of flow regimes, water temperatures, sediment levels, and other habitat <br />conditions caused by water depletions has contributed to the establishment of nonnative <br />fishes. Endangered fishes within the action area would experience increased competition <br />and predation as a result. <br />EFFECTS TO CRITICAL HABITAT <br />All four of the listed Colorado River fish require the same PCEs essential for their <br />survival. Therefore, we are combining our analysis of all four species into one section. <br />Because the amount of designated critical habitat varies for each of the four species, the <br />amount of habitat will vary; however, the effects would be the same for all critical habitat <br />within the action area. <br />Water, physical habitat, and the biological environment are the PCEs of critical habitat. <br />This includes a quantity of water of sufficient quality that is delivered to a specific <br />location in accordance with a hydrologic regime that is required for the particular life <br />stage for each species. The physical habitat includes areas of the Colorado River system <br />that are inhabited or potentially habitable. for use in spawning and feeding, as a nursery, <br />or serve as corridors between these areas. In addition, oxbows, backwaters, and other <br />areas in the 100-year floodplain, when inundated, provide access to spawning, nursery, <br />feeding, and rearing habitats. Food supply, predation, and competition are important <br />elements of the biological environment. <br />Primary Constituent Element - Water <br />The subject action would deplete up to 724 acre-feet/year from the Colorado River Basin. <br />Removing water from the river system changes the natural hydrological regime that <br />creates and maintains important fish habitats, such as spawning habitats, and reduces the <br />frequency and duration of availability of these habitats of the four endangered fish. In <br />addition, reduction in flow rates lessens the ability of the river to inundate bottomland, a <br />31