Effects of Fish Stocking and Fish Removal on Cascades Frogs (Rana cascadae) and Other Native Species

Karen L. Pope

Ecology Graduate Group & Entomology Dept, UC Davis

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ABSTRACT

POPE, KAREN L.1,2*, SHARON P. LAWLER1, AND HART W. WELSH2
1Ecology Graduate Group & Entomology Dept, UC Davis, kpope@ucdavis.edu; 2U.S. Forest Service Pacific SW Research Station, Redwood Sciences Laboratory.

Effects of Fish Stocking and Fish Removal on Cascades Frogs (Rana cascadae) and Other Native Species

We have completed three years of a four-year study testing the effects of introduced trout on the flow of insect and amphibian prey from lakes to predators in uplands. We are studying 4 historically fishless 'reference' basins, and 12 'treatment' basins under three management schemes: trout stocking, suspended stocking, and fish removals. Lakes are at elevations over 1,920 m in the Trinity Alps of California. In summer, 2003 we collected biweekly pre-treatment data at all basins, and in fall we initiated treatments. Sites are being re-sampled in summers 2004-6. We are surveying amphibians, snakes, aquatic insects, bats, and birds. The aquatic fauna did not differ among the three treatments before fish removal, but Cascades frogs, garter snakes and large-bodied insects were more numerous in reference lakes. In 2004 and 2005, recruitment of Cascades frogs, Pacific treefrogs and large aquatic insects improved dramatically in fish removal lakes. Preliminary results will be presented that focus on changes in amphibian populations and distributions across treatments during the first three years of the project.