Biological Contributions of Tributary Streams to the Wild Rogue River
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Tributary streams in the Wild Rogue basin provide critical biological benefits and services to aquatic species and riparian habitats. These streams supply fish habitat for anadromous fish (such as coho salmon and steelhead) which are estimated to be present in approximately 100 stream miles across fourteen tributary streams (BLM, Kelsey Whisky FEIS, 2003). Spawning and rearing habitat is of particular importance to listed “threatened” coho salmon that reside in these streams, as well as Klamath Mountain Province steelhead that are in decline (USFS 2005). Juvenile density studies of steelhead indicate that juvenile salmonids were present in 71% – 100% of high-order stream reaches monitored in the Rogue basin from 2002 to 2007, with an average of 90.8% presence (ODFW, Western Oregon Rearing Project 2002-2007). The habitat afforded by these streams contributes to the presence of salmonids throughout the larger watershed, and has been enough to merit specific attention to fishbearing streams in previous management plans and analyses (BLM, Wild Rogue – South Watershed Analysis, 2000).
The tributaries also contribute colder stream temperatures to the larger main Rogue River system. Stream temperature is a primary control on fish growth and productivity, and increasing stream temperatures can result in behavioral changes and fish mortality (Sullivan et al., 2000). The smaller creeks in the Rogue basin demonstrate lower summer averages and maximum temperatures compared to the main stem of the river, therefore ensuring they are valuable and vital coldwater thermal refugia for salmonids (Watershed Sciences, LLC, 2004; BLM Wild Rogue North Watershed Analysis, 1999; DEQ Lasar). Climate change effects on stream temperatures projected for the U.S. emphasize the importance of these streams as thermal refuges for anadromous fish. Studies indicate that changes to cold and cool water fish thermal habitats are predicted to be reduced by ~50% (Eaton and Scheller, 1996).
The importance of these Rogue basin tributaries in providing extensive riparian habitat and cooler stream temperatures is supported by the scientific literature and data, and has been highlighted in previous watershed analyses and plans by the BLM, the primary landmanaging agency in the lower Rogue basin. The Rogue streams currently receive protections under the Northwest Forest Plan (NWFP) that ensure that both perennial and intermittent fish-bearing and non-fish-bearing streams are buffered from detrimental management actions such as logging and road-building (Standards and Guidelines, 1994). However, if no action is taken, changes to the management of the lower Rogue River basin, proposed under the 2008 BLM Western Oregon Plan Revisions (WOPR), would ensure that these tributaries are made vulnerable to logging effects such as debris flows, sediment loading, increasing stream temperature, and degradation to riparian habitat (Suttle et al., 2004; Johnson and Jones, 2000). These impacts would also subsequently filter down to affect the health and productivity of the greater main stem of the Wild Rogue River.