Graduation Year

2022

Graduation Month

May

Document Type

Thesis

Degree Name

Bachelor of Science

School or Department

Wildlife Biology

Major

Wildlife Biology – Aquatic

Faculty Mentor Department

Wildlife Biology

Faculty Mentor

Lisa Eby

Keywords

westslope cutthroat trout, rainbow trout, survival, Rock Creek, Clark Fork River, Montana

Subject Categories

Aquaculture and Fisheries

Abstract

Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT) is a native trout species of conservation concern in Montana. Both migratory and resident life histories can be found in cutthroat from the same natal stream. Habitat degradation and hybridization with rainbow trout O. mykiss (RBT) have resulted in few genetically pure, migratory WCT populations persisting in large river systems. These WCT conservation populations are occurring more and more as isolated, resident populations in headwater streams. Rock Creek in Western MT has retained a unique population of migratory, non-hybridized WCT, and is of special conservation and ecological interest. As we work to protect WCT and migratory life histories, we need to better understand how these fish use habitats and how that habitat use may relate to subsequent survival. From 2018 to 2021, 80 of these WCT, along with 81 hybrids and 29 RBT had radio telemetry tags implanted to be tracked primarily for spawning migrations and habitat use. I used locations and mortality indicators from radio telemetry data collected over the course of the three-year study to examine how survival differed between fish with varied genetic ancestry and then examined whether there was a relationship between survival and habitat use. There was no significant difference in annual survival between different ancestries of Oncorhynchus spp. I combined all 190 fish in the study to examine the association between survival and habitat use. Fish spending the summer (June, July, and August) in Rock Creek showed much higher survival rates than those spending the summer in the Clark Fork River. I found major differences in the habitats in question, with substantially higher temperatures in the Clark Fork River versus Rock Creek, but are also correlated with lower flow and higher contaminant levels. Results of this study build a better understanding of how survival relates to habitat use and can be useful to help protect and prioritize habitats.

Honors College Research Project

Yes

GLI Capstone Project

no

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© Copyright 2022 Brett D. Traxler