Recovery Plan for the Northern Spotted Owl - DRAFT

affect fish habitat in different ways. In general, the effects of timber harvestingon fish habitat include increased sedimentation and water temperatures,changes in seasonal flow patterns, quantity and distribution of woody debris,and channel morphology (Chamberlin et al. 1991:181 -205).Quantity and timing of sediment entry into stream systems are important indetermining habitat quality for fishes. Specific substrate conditions arerequired for spawning, rearing, and over-wintering. Increases in fine sedimentfrom logging activities has been shown to decrease survival of salmonid fry(Scriver and Brownlee 1989). Substrate conditions also are important forsalamanders, aquatic insects and aquatic plants that contribute to energyprocessing in aquatic environments.When streamside trees are removed, increased light may stimulate primaryproduction (Murphy and Meehan 1991). Increased periphyton (algae andassociated microorganisms growing attached to any submerged surface)production after canopy removal may increase the abundance of invertebratesand fishes, mainly by increasing the quantity of detritus (Murphy and Meehan1991). Increased primary production from canopy removal may last for a shortperiod of time and then diminish due to canopy closure, which is often denserin even-age, second-growth forests than in older forests (Murphy and Meehan1991). In addition, cumulative downstream effects of increased water temperaturemay create downstream areas that are not suitable for native fishes.Among the most important long-term effects of forest management activities onfish habitat in western North America have been changes in distribution andabundance of large woody debris (more than 14 inches in diameter) in streams(Hicks et al. 1991). Large woody debris plays a critical role in controllingstream channel morphology, regulating the movement and storage of inorganicand organic material, and in creating and maintaining fish habitat (Hicks et al.1991). Debris removal was common in the 1960s and 1970s and often wasencouraged by fisheries biologists to improve fish access to upstream areas.Since then, the importance of woody debris in stream channel form andfunction has been recognized. Removal of large woody debris from streamchannels has been shown to affect fish populations adversely. Debris removalcan cause a decline in channel stability and a corresponding reduction in thequality and quantity of pools and cover (Hicks et al. 1991).Removal of large trees from riparian zones has caused long-term reduction inthe recruitment of large woody debris to stream channels, leading to a reductionin the quality of fish habitat (Hicks et al. 1991). Murphy and Koski (1989)modeled the depletion and input of large woody debris from second-growthforests. Their model indicated that 90 years later, clear-cut logging without abuffer strip would reduce large woody debris by 70 percent, and recovery toprelogging levels would take more than 250 years.The use of buffer strips has been shown to reduce the localized effects ofstreamside timber harvest. Murphy et al. (1986) found that streams withbuffer strips did not consistently differ from old-growth streams; streams inclear-cuts without buffer strips had more periphyton, lower channel stability,and less canopy, pool volume, large woody debris, and undercut banks thanstreams in old-growth forests.Summary.-Twenty-eight species comprising over 1,181 fish stocks wereidentified within the range of the northern spotted owl. A total of 766 stocks(Table D. 10) are 1) listed federally as threatened or endangered, 2) candidatesfor federal listing, 3) species of special concern (state), or 4) are considered atrisk by Nehlsen et al. (1991), Moyle et al. (1989), or Williams et al. (1989).These stocks occur in 348 streams throughout the Pacific Northwest (Tables373