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Item Success of westslope cutthroat trout and arctic grayling conservation translocations in Yellowstone National Park, Montana and Wyoming, USA(Montana State University - Bozeman, College of Letters & Science, 2021) Puchany, Andriana Rachel; Chairperson, Graduate Committee: Alexander V. ZaleRestoration of native Westslope Cutthroat Trout Oncorhynchus clarkii lewisi and fluvial Arctic Grayling Thymallus arcticus in Yellowstone National Park is a high priority for fishery managers. Restoration of the East Fork Specimen Creek and Grayling Creek watersheds included construction of fish barriers to isolate watersheds, application of rotenone to eliminate nonnative and hybridized fish, and translocations of native fish. We sampled these watersheds in 2018 and 2019 to evaluate the success of restoration efforts by 1) estimating the stage of recovery achieved by translocated populations, 2) determining contributions of Westslope Cutthroat Trout donor sources to the translocated populations in the East Fork Specimen Creek watershed by investigating their genetic ancestries, and 3) making comparisons of recovery between the East Fork Specimen and Grayling Creek watersheds. Recovery of Westslope Cutthroat Trout in both watersheds is progressing, with expected differences in stage of recovery between the two watersheds attributable to a 5-year difference in restoration timelines. Conversely, recovery of Arctic Grayling in Grayling Creek appears improbable without management intervention, but the surprising documentation of naturally reproduced individuals engenders a hopeful future for continued Arctic Grayling recovery efforts. Interspecific hybrid introgression discovered in Westslope Cutthroat Trout populations in East Fork Specimen and Grayling creeks probably resulted from barrier failure or incomplete eradication of hybrid fish during rotenone treatments. Whereas all Westslope Cutthroat Trout donor sources contributed to the recovering population in East Fork Specimen Creek, contributions were disproportionate to numbers translocated, indicating potential fitness differences among donor sources. Findings from this study have already helped Yellowstone National Park fishery managers make adaptive management decisions and will help inform future native fish conservation translocations.Item Small scale denil development for use in headwater streams in southwest Montana(Montana State University - Bozeman, College of Engineering, 2021) Conley, Megan Elizabeth; Chairperson, Graduate Committee: Kathryn Plymesser; Katey Plymesser, Kevin Kappenman, Matt Blank and Joel Cahoon were co-authors of the article, 'Arctic grayling (Thymallus arcticus) passage through a scaled denil fishway' submitted to the journal 'Journal of fish and wildlife management' which is contained within this thesis.The Big Hole River is located in an agricultural valley in Southwest Montana and is home to the last fluvial (river dwelling) population of Arctic grayling (Thymallus arcticus) in the contiguous United States. Grayling mostly populate the tributary streams in the upper portion of the watershed, where there are many irrigation diversions, which greatly fragments grayling's natural habitat. While many of these irrigation diversions have fish ladders installed at them to assist with habitat reconnection, these ladder become impassable when the water levels get too low in the system or irrigators chose to block the fish ladders in order to divert more water. This study investigated and characterized a smaller scale Denil fish ladder that would use less water while providing adequate fish passage. Three different flow rate calculations were applied to a series of scaled Denils to compare to the expected flow rates of the full scale Denil to determine the scaled sizes to construct. A 0.6 scale and a 0.75 scale Denil were selected and hydraulic lab testing confirmed that 25.4 cm baffle spacing was the best for both scaled models. The fish swimming study, conducted at the outdoor flume at the Bozeman Fish Technology Center, used eight hatchery-raised grayling in each of the eight treatments. Each treatment was repeated 3 times using the 0.6-scale model for a total of 24 trials with 192 fish. Each treatment used a different combination of headwater depth (between 30.5 cm and 61.0 cm) and tailwater depth (between 15.2 cm and 61.0 cm). The grayling passed with near perfect success at all headwater and tailwater combinations except when the head difference between the headwater and tailwater was at its greatest (61.0 cm headwater and 15.2 cm tailwater). This preliminary study showed that grayling are willing to pass smaller-scale structures at a variety of flow rates but did not test a wide range of slopes, age classes or fish sizes. These results should be useful to water managers when looking to modify or install new Denil fishways in the Big Hole River Basin and around the western United States.Item Life history and management of the American Grayling (Thymallus Signifer Tricolor) in Montana(Montana State University - Bozeman, College of Letters & Science, 1953) Nelson, Perry H.Item The reproduction of salmonids in the inlets of Elk Lake, Montana(Montana State University - Bozeman, College of Letters & Science, 1974) Lund, John Andrew