Increased Amphibian Presence In A Montane Lake After Fish Removal, Mount Rainier National Park, Washington

Abstract

During the period 1996–2003, a population of introduced Salvelinus fontinalis was eradicated from a montane lake in Mount Rainier National Park, Washington State, USA. Using mostly gill-nets, 2185 fish were removed. Snorkel and visual encounter surveys (n = 10 and 6, respectively) were completed 1996–2001, to document the apparent abundances of amphibian species present in the lake and an adjacent shallow pond during fish presence and removal. During this period only 7 Ambystoma gracile larvae and 6 Rana cascadae adults were observed in the lake; no amphibians were observed in the pond. After fish removal, lake snorkel and visual encounter surveys (n = 9 and 10, respectively) conducted between 2004 and 2015 collectively documented the apparent increase in abundances of A. gracilie (n = 398), A. macrodactylum (n = 68), Ambystoma spp. (n = 184), Rana cascadae (n = 357), and Ascaphus truei (n = 12). Pond visual encounter surveys conducted between 2005 and 2012 documented the increased presence of Ambystoma spp. (n = 110) and Rana cascadae (n = approximately 5600 ) larvae. Although the number of amphibian species detected and their apparent abundances varied among surveys and years, the abundances of the amphibian species in Hidden Lake increased markedly after removal of the introduced fish population.