Recovery Plan for the Northern Spotted Owl - DRAFT

Stock concept.-The term "stock" was adopted 51 years ago, shortly after thefirst attempts to describe stocks of Pacific salmon and discuss their importanceto management of the species (McIntyre 1983). After reviewing the results ofearly marking experiments, Rich (1939) concluded that Pacific salmon weredivided into many local populations or what we now refer to as stocks (Ricker1972). Anadromous salmonid species comprise populations that originatefrom specific watersheds as juveniles and generally return to their natalstreams to spawn. This life cycle results in a large degree of reproductiveisolation of interbreeding individuals or stocks (Ricker 1972). Stocks representunique genetic entities, and loss of a stock is irreversible. It is at the stocklevel that conservation and management of salmon is taking place. Additionaldocumentation and discussion of fish stocks can be found in NehIsen et al.(1991).Effects of land-use activities on fishes and fish habitat.-The condition ofwatersheds dictates the physical and chemical makeup of the streams thatdrain them and of the lakes that lie within them (Meehan 1991). Vannote et al.(1980) proposed a "river continuum concept" based on a continuous gradientin physical variables within a river system from headwaters to mouth. Thisgradient leads to a continuum of biotic adjustments and consistent patterns ofloading, transport, utilization, and storage of organic matter along the length ofa river (Vannote et al. 1980). Management of fish habitat, and therefore fishpopulations, requires consideration of the habitat within the watershed toaccommodate stream and terrestrial processes that work in concert throughoutthe basin.Gradients within the "river continuum" also provide a basis for assessingcumulative effects. For example, fine sediment is transported from highgradient to low gradient areas, where it can accumulate to levels that affectfisheries. The translocation downstream and the contribution from severalsources make traditional cause-and-effect evaluation of cumulative effectsdifficult, if not impossible. Multiple ownerships complicate the issue and mayimpede evaluation of upstream effects.Many land-use activities can affect aquatic habitat and fish populations. Suchactivities include road construction, timber harvest, livestock grazing, hydroelectricdevelopment, chemical applications, mining, and recreation. Theeffects of road construction and timber harvest, which are significant withinthe range of the spotted owl, are discussed here.Roads.-Roads can modify natural drainage systems and accelerate erosionprocesses; these changes can alter physical processes in streams, leading tochanges in streamflow regimes, channel configuration, sediment transport andstorage, substrate composition, and stability of slopes adjacent to streams(Furniss et al. 1991). Increased sediment input from roads can affect fishhabitat. The principle source of sediment entering streams is by mass soilmovements and surface erosion processes (Swanston 1991), although forestroads can substantially increase the frequency of mass soil movements insteep watersheds (Everest et al. 1987). Furniss et al. (1991:297-323) foundthat rarely can roads be constructed without some effect on fish habitat.However, roads that have been properly planned, constructed, and maintainedhave minimized these effects. Regular maintenance of roads to reduce impactson fish habitat should be practiced on all roads, not just those that are activelyused.Timber harvest.-Effects of timber harvest and silvicultural treatments(planting, thinning, burning, mechanical site preparation, and application ofchemicals) on stream ecosystems are complex (Meehan 1991). Various timberharveststrategies ranging from clear-cutting to long-rotation selective harvest,372