Date of Award
Spring 2024
Rights
Access is available to all users
Document Type
Thesis
Degree Name
Master of Science (MS) in Biology
Department
Biology
Abstract
Numerous salmonid species demonstrate diverse life histories, encompassing both resident and migratory behaviors. Migratory life histories play a pivotal role in maintaining metapopulations for various reasons, facilitating genetic exchange between populations and yielding larger-sized females with increased fecundity relative to residents. This study took place in northern Idaho, within the lower Priest River system, which is highly susceptible to degrading habitat. Previous research has discovered this system as a significant contributor to migratory Westslope Cutthroat Trout (Oncorhynchus lewisi, WCT) in the Lake Pend Oreille and Priest River systems. Expanding on these results, we compared four Priest River tributaries that produced high proportions of migratory individuals (North Fork East River, Big, Saddler, and Quartz Creeks), and compared them to four tributaries that produced low migratory proportions (Benton, Kavanaugh, Uleda, and Keokee Creeks). In each of the eight tributaries, fish density was collected using multi-pass depletion estimates. Additionally, stream temperature and flow velocity were measured separately. With the use of a generalized boosted regression model, in r version 4.2.2, maximum temperature had the largest influence in explaining migratory behavior. Among all eight tributaries, Big Creek produced the highest number of migratory individuals, with 31 out of 70 individuals recorded. It also experienced the warmest temperature at 19.13°C. Notably, it reached its peak maximum temperature earliest on August 15th and sustained a warmer temperature for an extended duration compared to all other tributaries. As temperatures rise beyond the optimal range for salmonids, individuals may leave these tributaries to avoid mortality. This behavior could also be driven by the advantage of expressing a migratory life history, which allows them to thrive in more suitable environments. Our results suggest that there is a combination of factors that are influencing the expression of migratory life histories. Some potential ideas to investigate to better understand these factors may be observing the invertebrate communities, seasonal differences, and comparable variables in other Pend Oreille River tributaries that can be compared to the Priest River.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Keenan, Kyle M., "Investigating the relationships between biotic and abiotic factors affecting migratory behavior in Westslope Cutthroat Trout within the Priest River System" (2024). EWU Masters Thesis Collection. 931.
https://dc.ewu.edu/theses/931
