Non-native salmonids affect amphibian occupancy at multiple spatial scales

Publication Type:

Journal Article

Authors:

Pilliod, David S.; Hossack, Blake R.; Bahls, Peter F.; Bull, Evelyn L.; Corn, Paul Stephen; Hokit, Grant; Maxell, Bryce A.; Munger, James C.; Wyrick, Aimee

Source:

Journal of Conservation Biogeography, Blackwell Publishing, Volume 16, Issue 6, p.959-974 (2010)

Call Number:

A10PIL01IDUS

URL:

www.blackwellpublishing.com/ddi

Keywords:

Ambystoma macrodactylum, Columbia Spotted Frog, Long-toed Salamander, Rana luteiventris

Abstract:

The introduction of nonnative species into aquatic environments has been linked with local extinctions and altered distributions of native species. The authors investigated the effect of nonnative salmonids on the occupancy of two native amphibians, the long-toed salamander (Ambystoma macrodactylum) and Columbia spotted frog (Rana luteiventris), across three spatial scales: water bodies, small catchments and large catchments. Between 1986 and 2002, they surveyed 2,267 water bodies (lakes) at 1500 m or above in elevation across the northern Rocky Mountains for amphibian occupancy (with evidence of reproduction) and fish presence. They also modeled the probability of amphibian occupancy at each spatial scale in relation to habitat availability and quality and fish presence. After accounting for habitat features, the authors estimated that A. macrodactylum was 2.3 times more likely to breed in fishless water bodies than in water bodies with fish. Ambystoma macrodactylum also was more likely to occupy small catchments where none of the water bodies contained fish than in catchments where at least one water body contained fish. However, the probability of salamander occupancy in small catchments was also influenced by habitat availability (i.e., the number of water bodies within a catchment) and suitability of remaining fishless water bodies. No relationship was found between fish presence and salamander occupancy at the large-catchment scale, probably because of increased habitat availability. In contrast to A. macrodactylum, no relationship between fish presence and R. luteiventris occupancy was found at any scale. Results suggest that the negative effects of nonnative salmonids can extend beyond the boundaries of individual water bodies and increase A. macrodactylum extinction risk at landscape scales. The authors suspect that niche overlap between nonnative fish and A. macrodactylum at higher elevations in the northern Rocky Mountains may lead to extinction in catchments with limited suitable habitat.