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5elantlfir T:valuatlon of Riplo®IeaI opinlona on Endangered and Th=tcnccl righcr In the KlarAath River Bain: Tntcrlm RrWrt (2002) <br />nnp;maw+..+mp artW.+pennnnkNgiwmx �7almm+ i1� hon6 tnpwight 2114, MIL TNe Nai lnna+ AQ&MV 4 v l ilom all Ilph- �t%rVtd <br />3. Evaluation of-the Biological Opinion on <br />Klamath Basin Coho Salmon <br />Coho salmon enter the main stem of the Klamath River for spawning typically in <br />their third year, primarily between October sad December. Over most of this interval, <br />main -stem flows below Iron Gate Dam often are high (ca. 2500 -3000 afs: NMFS 2001). <br />Thus, standard methods for observing and counting spawning fish are not easily applied, <br />and the size of the spawning population is unknown. Approximations put the entire ESU <br />at about 10,000 spawning coho salmon of lion-hatchery origin per year (Weitkamp et al. <br />1995), of which only a small portion is associated with the Klamath Basin, where several <br />important tributary runs have been reduced to a handful of individuals (NMFS 2001). <br />Spawning coho in the Klamath Basin are restricted to use of tributaries that they <br />can reach from the main stem up to Iron Gate Dam. Original spawning runs probably <br />were largest in large tributaries, but presently are restricted mainly to numerous small <br />tributaries entering the main stem directly (Yurok Tribe 2001). Large tributaries have <br />been severely degraded, show excessively high temperatures, and are dammed in critical <br />places. Although a minor amount of spawning and growth may occur in the main stem. <br />the main stem serves adults primarily as a migration route. <br />Fry appear in late fall or winter, when water levels are highest. Most fry probably <br />remain in the tributaries but some may move to or be swept into the main stem. Juvenile <br />coho become smolts and emigrate to the ocean between March and mid -June, peak <br />migration occurs in mid -May (NUTS 2001). In general, juvenile coho can be expected to <br />occupy places where summer temperatures are low (12 -14 °C appears to be optimal for <br />growth). They are also favored by deep pools with complex cover, especially large <br />woody debris, which is essential for survival over winter (Sandercock 1991). Such <br />conditions exist primarily in tributary streatns of the Klamath Basin. <br />The reduction in stocks of native coho salmon in the Klamath River Basin has <br />been caused by multiple interactive factors. 'Drastic reduction in spawning and juvenile <br />habitat has occurred through impoundment and physical alteration of tributaries. Also, <br />Large numbers of smelts are released annually from the Iron Gate hatchery. These <br />fish, which are derived from a combination of Klamath Basin and Columbia River coho, <br />likely compete with or have other negative effects on wild native coho at all stages of <br />their life history during which they are in contact, including the smoltification- emigration <br />period, the ocean growth period, and spawning (Fleming and Gross 1993, Nielsen 1994, <br />NRC 1996). <br />Physical habitat in the main stem is a potential concern for the welfare of the coho <br />in several life stages. The spawning run must have adequate flows for passage, which <br />would be impaired by excessively shallow water (e.g., through amplification of predation <br />losses). Access to tributaries is a related consideration for the spawning run, given that <br />little if any spawning occurs in the main stem. Also, fry that enter the main stem must <br />find cool, well- shaded pools, or return to a suitable tributary. Smolts moving <br />downstream must find suitable temperature, flow, and habitat conditions compatible with <br />their physiological transformation+ during migration (Wedemeyer et al. 1980). <br />While habitat is an undeniable requirement for all life stages, the assessment of <br />17 <br />986 -d 660/060*d 9EZ -1 899899BEOE snnosu 1daf m 100 —mad EV:H ZOOZ- 80 -83d <br />