Klamath Network Amphibian and Fish Inventory

We conducted a cooperative inter-agency investigation into the status of native amphibians and nonnative fishes in lentic habitats at Lassen Volcanic National Park. Census surveys at Lassen Volcanic National Park were conducted during summer 2004, and results of surveys that we conducted in the Thousand Lakes and Caribou Wilderness areas during summer 2002 are also presented here. Visual encounter surveys were conducted to identify presence, species, life stage and relative abundance of amphibians, and timed gill net sets or visual surveys were used to identify fish presence, species, and relative abundance. Habitat data were also collected. We analyzed the data in two different ways. One analysis uses the Mann-Whitney U test and multinomial logistic regression to examine attributes of historically stocked lakes potentially contributing to the observed presence or absence of fish. In the second analysis we use generalized additive models to examine site attributes associated with amphibian occurrences, including the presence or absence of fish. Herpetofauna detected include the Pacific treefrog (Hyla regilla), western toad (Bufo boreas), long-toed salamander (Ambystoma macrodactylum), Cascades frog (Rana cascadae), rough-skinned newt (Taricha granulosa), western terrestrial garter snake (Thamnophis elegans), and the common garter snake (T. sirtalis). Fish species detected include three species of trout (Family: Salmonidae), five minnow species (Family: Cyprinidae), and the Tahoe sucker (Catostomus tahoensis). Of the confirmed historically stocked lakes at LVNP, both the number of inlets present, and size of water bodies (both perimeter and area), was significantly greater at lakes that continue to support fish, while the elevations were significantly lower, compared to those sites that have gone fishless. The model best able to predict which lakes would revert to a fishless condition included only the number of inlets and perimeter. Our models suggest that populations of long-toed salamanders and Pacific treefrogs are less likely to be found in water bodies supporting fish. Fairy shrimp also appear to be negatively affected by fish. The Cascades frog was only detected at three sites, and could not be analyzed statistically. We believe that the Cascades frog is in immediate risk of extirpation from the Lassen region. Although fish clearly adversely affect palatable amphibian species, a number of considerations lead us to believe that fish are not the main driver behind the observed regional decline of Cascades frog. Factors outside the scope of this investigation, such as pollution and disease, may play an important role in declines observed in the Lassen region.

Klamath Network Amphibian and Fish Inventory

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