Local and Landscape Effects of Introduced Trout on Amphibians in Historically Fishless Watersheds |
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Authors: | David S Pilliod Charles R Peterson |
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Institution: | (1) Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209-8007, USA, US |
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Abstract: | Introduced trout have often been implicated in the decline of high-mountain amphibian populations, but few studies have attempted
to understand whether fish stocking also influences the distribution and abundance of amphibians throughout entire mountain
basins, including the remaining fishless lakes. We examined this relationship using the relative abundance of long-toed salamanders
(Ambystoma macrodactylum) and Columbia spotted frogs (Rana luteiventris) in fish-containing and fishless lentic sites in basins with varying levels of historic fish stocking. All lentic waters
were surveyed for fish and amphibians in 11 high-elevation basins in the Frank Church-River of No Return Wilderness, Idaho,
between 1994 and 1999. We found introduced trout (Oncorhynchus clarki, O. mykiss, O. m. aguabonita) in 43 of the 101 sites, representing 90% of the total surface area of lentic water bodies available. At the scale of individual
water bodies, after accounting for differences in habitat characteristics between fish-containing and fishless sites, the
abundance of amphibians at all life stages was significantly lower in lakes with fish. At the basin scale, densities of overwintering
life stages of amphibians were lower in the fishless sites of basins where more habitat was occupied by trout. Our results
suggest that many of the remaining fishless habitats are too shallow to provide suitable breeding or overwintering sites for
these amphibians and that current trout distributions may eventually result in the extirpation of amphibian populations from
entire landscapes, including sites that remain in a fishless condition.
Received 28 March 2000;Accepted 2 January 2001. |
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Keywords: | :Ambystoma macrodactylum amphibian extinction fish stocking introduced trout metapopulation persistence Rana luteiventris wilderness |
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