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1 <br />1 <br />t <br />[1 <br />1 <br />1 altering the natural food base, increasing hybridization with other similar species, and <br />2 subjecting the chub to higher levels of mortality from introduced predators, competitors, <br />3 parasites, and diseases. Dams have also fragmented chub habitat areas, blocking fish <br />4 passage and preventing gene flow between the remaining populations. Further, federal <br />5 and state agencies have introduced nonnative fish to the Colorado River Basin. The <br />6 introduced fish, such as brown trout, rainbow trout, and channel catfish, compete with <br />7 and prey on humpback chub. <br />8 22. Due to these threats, the humpback chub is an "endangered species," <br />9 meaning it is in danger of extinction throughout all or a significant portion of its range. <br />10 See 16 U.S.C. § 1532(6) (defining endangered species). The humpback chub was first <br />11 recognized as an endangered species in 1967. 32 Fed. Reg. 4001 (March 11, 1967). The <br />12 chub was placed on the endangered species list when the ESA was passed in 1973. <br />13 23. On March 21, 1994, Defendants designated critical habitat for the <br />14 humpback chub. 59 Fed. Reg. 13374. Under the ESA, the designation of critical habitat <br />15 is an inventory of habitat areas essential for the survival and recovery of listed species. <br />16 Critical habitat serves to identify those areas where recovery efforts are to be <br />17 concentrated. Critical habitat includes both occupied and unoccupied habitat. 16 U.S.C. <br />18 § 1532(5). <br />19 24. For the humpback chub, Defendants designated seven habitat stretches of <br />20 the Colorado River system as critical habitat, which constituted approximately 28 <br />21 percent of the chub's historic range. 59 Fed. Reg. at 13384. Within Grand Canyon <br />22 National Park, FWS designated critical habitat from Nautiloid Canyon west to Granite <br />23 Park on the Colorado River's mainstem, and the lower eight miles of the Little Colorado <br />24 River, a tributary to the Colorado River. FWS defined chub critical habitat as (1) water <br />25 in the quantity and quality needed for all its life stages, (2) the physical river habitat <br />26 features that are suitable for spawning, nursing, feeding and rearing, and (3) the <br />27 biological environment which provides sufficient food supply and includes a natural <br />28 balance of predation and competition from nonnative species. <br />Complaint 8 <br />Case 3:07 -cv- 08164 -DGC Document 1 Filed 12/07/2007 Page 8 of 20 <br />