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ScIonriflc Mralumlon ofMi <br />ttnp.�rmtv�.naf cAUfnrcnhnntlrp�f)nNt� <br />Ical Opinlong on rndangrmd anti Th=tcncd r ahca In the Klamath RIvor Rosin: Tomlin RcpolT (2002) <br />mVlJlQ LeojgApltl vmm d1I1I'Lite Narinaal Arudary nrscloxi. ull fightt rMrY C <br />Summary <br />e Klamath River Basin, which drains directly to the Pacific from parts of <br />southern gon and northern California, contains endemic freshwater fishes and <br />genetic y distinctive stocks of anadtomous fishes. Endemic freshwater fishes include <br />the she se sucker (Chasrraistlss breviroslris) and the Lost River sucker (Deltastes <br />luxatus). These long -lived and relatively large species, which live primarily in lakes but <br />enter flo ins waters or springs for spawning, were sufficiently abundant during the <br />ninete and early twentieth century to support commercial fisheries. During the last <br />half of twentieth century these species declined so much in abundance that they were <br />listed in 988 as endangered under the federal Endangered Species Act (ESA). In <br />addition, the genetically distinctive Southern Oregon/Northern California Coasts <br />(SONCC) coho salmon (Oncorhynchus kisutch), in evolutionary significant unit (ESU) <br />of the coho salmon, depends on the Klamath River main stem for migration and on <br />tributary waters for spawning and growth before entering the Pacific for maturation. The <br />Klamath Basin coho has declined substantially over the last several decades, and was <br />listed as threatened under the ESA in 1997. <br />Factors contributing to the decline in abundance of the endangered suckers and <br />threatened coho in the Klamath River Basin are diverse and in some cases incompletely <br />documented. Factors thought to have contributed to the decline of the endangered <br />suckers include degradation of spawning habitat, deterioration in the quality of water in <br />Upper Klamath Lake, overexploitation by cornsnercial and non - commercial fishing (now <br />regulated), introduction of competitive or predaceous exotic species, blockage of <br />migration routes, and entrainment of fish of all ages in water management structures. <br />Factors contributing to the decline of coho salmon are thought to include earlier <br />ovcmploitation by fishing as well as continuing degradation of tributary habitat and <br />reduced access to spawning areas. The threatened coho salmon also may be affected by <br />changes in hydrologic regime, substantial warming of the main stem and tributaries, and <br />continuing introduction of large numbers of hatchery- reared coho, which are derived only <br />partly from native stock. <br />The U.S. Bureau of Reclamation's (USBR) Klamath Basin Project (Klamath <br />Project) is a system of main-stem and tributary dams and diversion structures that store <br />and deliver water for agricultural water users in the Upper Klamath Basin under contract <br />with the USBR. Subsequent to the listing of suckers in 1988 and coho in 1997, the <br />USSR was required to assess the potential impairment of these fishes in the Klamath <br />River Basin by operations of the Klamath Project. In the assessments, which were <br />completed in 2001, the USBR concluded that operations of the project would be harmful <br />to the welfare of the listed species without specific constraints on water levels in the lakes <br />to protect the endangered sockets and flows in the Klamath River main stem to protect <br />the threatened coho salmon. <br />After release of the USBR assessment on the endangered suckers (February <br />2001), and following procedures required by the ESA, the U.S. Fish and Wildlife Service <br />(USFWS) in April 2001 issued a biological opinion based on an extensive analysis of the <br />relevant literature and field data. The biological opinion states that the endangered <br />966 -d BEO /M 'd 9EZ -1 899E998EOE sn nOs a innivN 100 -mu0 BE :II ZOOZ-80 -93d <br />