Tuolumne River Report - U.S. Fish and Wildlife Service

INTRODUCTION1.3 CLARIFICATION OFTERMINOLOGY1.3.1. Restoration versus RehabilitationThe term “restoration” often implies a return to apreferable or pristine condition that existedhistorically. Unfortunately, barring removal of thedams, cessation of agricultural and miningactivities within the valley, elimination of waterdiversion and other large-scale changes, returningto a pre-settlement Tuolumne River corridor isimpossible. “Rehabilitation” more realisticallydescribes our task outlined in this RestorationPlan, which is to improve conditions within theTuolumne River corridor to the fullest extentpossible given fluvial geomorphic, hydrologic,and societal constraints, with the understandingthat a complete return to pre-degraded conditionsand salmon population levels is not feasible.Figure 1-3 illustrates these concepts. We willcontinue, however, to use the more familiar term“restoration” throughout. The reader must keep inmind that what is intended is “rehabilitation” tohelp achieve the goals of the Settlement Agreement.Defining the restoration needs of the TuolumneRiver must be based on a sound foundation ofinformation and understanding that will lead tothe greatest chance for improving the rivercorridor. A restoration plan must also have afoundation in river ecology (Stanford et al. 1996).Figure 1-5. Different states of ecosystem recovery based on changesin ecosystem structure and function (modified from Bradshaw, 1984).Note that restoration is near or at original ecosystem structure andcomplexity. Rehabilitation improves ecosystem structure andcomplexity, but not to original (historical) levels.This Restoration Plan incorporates both foundations.Therefore, while chinook salmon are aprimary target species, the health and integrity ofthe ecosystem are given equal priority.1.3.2. Historical salmonid populationsThe Tuolumne River historically supported at leastthree major runs of anadromous salmonids (seagoingruns): fall-run and spring-run chinooksalmon (Oncorhynchus tshawytscha), andsteelhead trout (Oncorhynchus Mykiss). Theseruns differed in both timing of major life-historystages such as upstream migration, spawning,duration of residence in freshwater, and emigrationto the Pacific Ocean, as well as their adaptationsto instream habitat. The fall-run salmonhistorically spawned during fall and early wintermonths in the mainstem reaches of Central Valleyrivers below the foothills, up to approximately1,000 ft in elevation. In contrast, the spring-runsalmon ascended higher into accessible tributariesabove the foothills, and depended on cold-waterholding habitat during warm summer months,before spawning during fall and early wintermonths (Healey 1991, Yoshiyama et al. 1998).Steelhead trout also ascended higher into CentralValley tributaries to spawn during late-fall andwinter months. Because of these general differencesin life history timing and habitat requirements,each run responded uniquely to major landuse developments that have occurred during thepast century. The spring-run chinookpopulation, believed to have been themost abundant salmon in the SanJoaquin River basin, is now extinct,blocked from its former over-summeringand spawning habitat by dams. Thesteelhead may still persist in relativelysmall numbers, but debate over itshistorical distribution and less emphasisin its commercial value has shiftedthe primary focus away from restoringa viable steelhead run. Only the fall-runchinook salmon run has persisted inappreciable numbers during the lastfew decades, and now retains thedistinct status in the San Joaquin Riverbasin and the Tuolumne River as apotentially viable commercial andrecreational fishery worthy of significantand costly basin-wide restorationefforts.CHAPTER 15