Invasion by nonnative brook trout in Panther Creek, Idaho : roles of habitat Quality, Connectivity and Biotic Resistance

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

Matthew R. Dare


Theoretical models suggest the invasion of nonnative freshwater species is facilitated through the interaction of three factors: biotic resistance, habitat quality, and connectivity. We measured variables that represented each component to determine which were associated with small (<150 >mm) and large (≥150 mm) brook trout occurrence in Panther Creek, a tributary to the Salmon River, Idaho. The abundance of rainbow trout was used as a measure of biotic resistance. Habitat variables included summer and winter temperature, instream cover, and channel size. Lastly, beaver ponds may play an important role in sustaining connected source populations of brook trout; therefore, we measured valley bottom area, which is correlated with the presence of beaver ponds. A composite model, using Akaike's information criterion, for large brook trout included habitat and biotic variables, however, results were inconclusive (odds ratio confidence interval overlapping 1.0) suggesting a more complex association between large brook trout and the variables measured, perhaps due to a more mobile life stage. For small brook trout, winter degree days and maximum summer temperature were the most important model variables and positively associated with presence. For both size classes, rainbow trout abundance showed insufficient evidence to confirm or exclude the importance of biotic resistance to the occurrence of brook trout. The results of this study indicate that habitat, specifically temperature, plays an important role in the occurrence of brook trout; however biotic resistance and connectivity may also play important roles and are worthy of further investigation.

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