Developing a Watershed-based Reserve System for Native Aquatic Species in the Sierra Nevada, California

Roland A. Knapp University of California Sierra Nevada Aquatic Research Lab, Mammoth Lakes, CA

Kathleen R. Matthews US Forest Service Pacific Southwest Research Station, Berkeley, CA

The decline of several native aquatic species from high mountain lakes in North America is at least partially due to the introduction of non-native trout. Despite an increasing interest in these native species, especially amphibians, there have been few attempts to restore native species habitat by eradicating introduced trout populations. Such efforts are currently hindered by a poor understanding of the importance of introduced trout relative to other factors in causing the decline of native species, lack of site-specific information on the distribution of native aquatic species and introduced trout, and few practical means of eradicating trout populations.

To improve our understanding of the effects of introduced trout on native aquatic species in the Sierra Nevada, California, we surveyed 2,200 lakes and ponds in the John Muir Wilderness and Kings Canyon National Park for fish, amphibians, zooplankton, and benthic macroinvertebrates. This research indicated that several native lake-dwelling species are impacted by introduced trout, that of these species the mountain yellow-legged frog, Rana muscosa, is the most at risk of extirpation, and that the decline of the mountain yellow-legged frog is primarily the result of trout introductions. In conjunction with this research, we also developed a means of eradicating trout populations from lakes using intensive gill-netting.

To begin the process of restoring the mountain yellow-legged frog to habitats across its historic range, we designed a reserve system for four watersheds located within the John Muir Wilderness. To design this reserve system, we utilized information on the current distribution of trout and mountain yellow-legged frogs, self-sustainability of trout populations, likelihood of successful trout eradication, and habitat suitability for mountain yellow-legged frogs. In cooperation with the California Department of Fish and Game, implementation of this reserve system began in 1997 with the eradication of trout populations from several lakes. If these efforts prove successful in expanding the current distribution of the mountain yellow-legged frog, our reserve design could serve as a model for future larger-scale restoration efforts throughout the Sierra Nevada.

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