Factors influencing the distribution of native bull trout and westslope cutthroat trout in western Glacier National Park, Montana

Northwest Science
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Abstract

The widespread declines of native bull trout (Salvelinus confluentus) and westslope cutthroat trout (Oncorhynchus clarkii lewisi) populations prompted researchers to investigate factors influencing their distribution and status in western Glacier National Park, Montana. We evaluated the association of a suite of abiotic factors (stream width, elevation, gradient, large woody debris density, pool density, August mean stream temperature, reach surface area) with the occurrence (presence or absence) of bull trout and westslope cutthroat trout in 79 stream reaches in five sub-drainages containing glacial lakes. We modeled the occurrence of each species using logistic regression and evaluated competing models using an information theoretic approach. Westslope cutthroat trout were widely distributed (47 of 79 reaches), and there appeared to be no restrictions on their distribution other than physical barriers. Westslope cutthroat trout were most commonly found in relatively warm reaches downstream of lakes and in headwater reaches with large amounts of large woody debris and abundant pools. By contrast, bull trout were infrequently detected (10 of 79 reaches), with 7 of the 10 (70%) detections in sub-drainages that have not been compromised by non-native lake trout (S. namaycush). Bull trout were most often found in cold, low-gradient reaches upstream of glacial lakes. Our results indicate that complex stream habitats in sub-drainages free of non-native species are important to the persistence of native salmonids in western Glacier National Park. Results from this study may help managers monitor and protect important habitats and populations, inform conservation and recovery programs, and guide non-native species suppression efforts in Glacier National Park and elsewhere.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Factors influencing the distribution of native bull trout and westslope cutthroat trout in western Glacier National Park, Montana
Series title Northwest Science
DOI 10.3955/046.087.0101
Volume 87
Issue 1
Year Published 2013
Language English
Publisher Northwest Scientific Association
Publisher location Cheney, WA
Contributing office(s) Northern Rocky Mountain Science Center
Description 11 p.
First page 1
Last page 11
Country United States
State Montana
Other Geospatial Glacier National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N