Laserfiche WebLink
The critical habitat unit within the action area (the Colorado River below Salt Creek to <br />Lake Powell) has been identified in the recovery goals for each of the four endangered <br />fish species (USFWS 2002a, b, c, d) as essential for the conservation of the species. <br />Critical habitat in the action area represents approximately 17 percent of the total critical <br />habitat for Colorado pikeminnow. Colorado pikeminnow is a wide ranging species <br />sometimes migrating extensive distances. to carry out life history functions. The action <br />area also encompasses a large area of razorback sucker critical habitat. Natural <br />reproduction of razorback sucker is very rare. Critical habitat for humpback chub and <br />bonytail are limited to shorter reaches of the Colorado River within critical habitat for <br />Colorado pikeminnow and razorback sucker. These shorter reaches include unique <br />habitats required for humpback chub and bonytail that are found in only a few other <br />places in the Colorado River basin. <br />EFFECTS OF THE ACTION <br />EFFECTS To ENDANGERED SPECIES <br />The subject project would adversely affect Colorado pikeminnow, razorback sucker, <br />bonytail, and humpback chub by reducing the amount of water in the river system upon <br />which they depend by up to 724 acre-feet/year. The effects to all four species primarily <br />result from the effects of the action upon their habitats. In general, the proposed action <br />would adversely affect the four listed fish by reducing the amount of water available to <br />them, increasing the likelihood of water quality issues, increasing their vulnerability to <br />predation, and reducing their breeding opportunities by shrinking the amount of breeding <br />habitat within their range. <br />Removing 724 acre-feet/year from the Colorado Rivers would change the natural <br />hydrological regime that creates and maintains important fish habitats, such as spawning <br />habitats, and reduces the frequency and duration of availability of these habitats of the <br />four endangered fish. The reduction of available habitats will directly affect individuals <br />of all four species by decreasing reproductive potential and foraging and sheltering <br />opportunities. Many of the habitats required for breeding become severely diminished <br />when flows are reduced. As a result, individual fish within the action area may not be <br />able to find a place to breed, or will deposit eggs in less than optimal habitats more prone <br />to failure or predation. In addition, reduction in flow rates lessens the ability of the river <br />to inundate bottomland, a source of nutrient supply for fish productivity. Water <br />depletions also exacerbate competition and predation by nonnative fishes by altering flow <br />and temperature regimes toward conditions that favor nonnatives. <br />The proposed depletions affect the water quality in the action area by increasing <br />concentrations of heavy metals, selenium, salts, pesticides, and other contaminants. <br />Increases in water depletions will cause associated reductions in assimilative capacity and <br />dilution potential for any contaminants that enter the river. The project depletions would <br />cause a proportionate decrease in dilution, which in turn would cause a proportionate <br />increase in heavy metal, selenium, salts, pesticides, and other contaminant concentrations <br />in the Colorado River to Lake Powell. An increase in contaminant concentrations in the <br />river would likely result in an increase in the bioaccumulation of these contaminants in <br />30