Theses and Dissertations at Montana State University (MSU)
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Item Westslope cutthroat trout passage in a scaled Denil fishway(Montana State University - Bozeman, College of Engineering, 2023) Buller, Cole John; Chairperson, Graduate Committee: Kathryn Plymesser; This is a manuscript style paper that includes co-authored chapters.Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) are a species of concern in the state of Montana and has become the focus of conservation efforts and research. Habitat fragmentation, caused by structures such as dams, culverts, and weirs, is one of the largest threats to Westslope Cutthroat Trout. Denil fishways have been installed at low-head diversions to facilitate their movement past these structures and maintain habitat connectivity. Recent research has focused on scaled Denil fishways, which require less water for operation than standard sized Denil fishways and leave more water for competing uses such as agricultural irrigation. The purpose of this study was to examine the passage of Westslope Cutthroat Trout in a 0.6-scale Denil fishway to determine the hydraulic conditions that best allow for passage. To do this, we prescribed twelve treatments of headwater and downstream approach depth combinations. Each treatment was replicated three times for a total of 36 trials with 10 fish in each trial. Fish movements and passage efficiencies were tracked using PIT tag telemetry. Overall, 68% (256/379) of the fish successfully passed through the fishway. Mixed effects statistical modeling was used to relate passage success to hydraulic variables and fish length. Results from this analysis indicate headwater to tailwater depth ratio and bulk tailwater velocity (as measured at the downstream end of the fishway) are the best metrics to predict the passage efficiency of Westslope Cutthroat Trout in a scaled Denil fishway. In general, passage success increased with lower headwater to tail water depth ratios (i.e., depths at the up and downstream ends of the fishway are similar) and lower tailwater velocities.Item Assessment of the Yellowstone Lake food web during lake trout suppression and Yellowstone cutthroat trout recovery informs conservation benchmarks(Montana State University - Bozeman, College of Letters & Science, 2022) Glassic, Hayley Corrine; Chairperson, Graduate Committee: Christopher S. Guy; This is a manuscript style paper that includes co-authored chapters.The collapse of native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri (hereafter cutthroat trout) in Yellowstone Lake was caused by predation by invasive lake trout Salvelinus namaycush. As an ecosystem with a low-diversity fish assemblage and several longterm data sets, Yellowstone Lake provided a unique opportunity to evaluate the influence of an invasive salmonid population undergoing suppression beyond only predator-prey dynamics. Diet data for cutthroat trout and lake trout were evaluated at varying densities to determine the effects of density on diet composition and diet plasticity. During the lake trout high-density state, lake trout consumed fewer native cutthroat trout and switched to amphipods, which were also consumed by cutthroat trout, resulting in high diet overlap between the species. As suppression reduced invasive lake trout densities, lake trout returned to consuming cutthroat trout and diet overlap was released. A shift in lake trout delta 13C signatures from the high-density state to the moderate-density state also corroborates higher consumption of cutthroat trout and invasive lake trout diet plasticity. Beyond predator-prey dynamics of lake trout and cutthroat trout, the invasion of lake trout caused > or = 25% change in energy flux for all organisms in Yellowstone Lake except for copepods. Food-web functional state did not change among food webs, but percentage of functional state contributing to total flux did vary. Herbivory was the dominant food-web functional state for all years, with the greatest percentage of flux from herbivory in 2011. In addition, by using a whole-ecosystem model that accounted for whirling disease and historical (natural) lake-level variation, I show that suppression of the lake trout population is necessary for cutthroat trout recovery, but the amount of suppression effort needed for cutthroat trout to reach recovery benchmarks is linked to severity of climate change. Additionally, if climate change increases the frequency and severity of reduced lake levels in the future, cutthroat trout recovery benchmarks may need to be adapted. With this research, I demonstrate how the feedbacks among predator-prey dynamics, disease, and climate change can complicate the suppression of invasive species and the conservation of invaded ecosystems and must be considered for establishing realistic conservation benchmarks.Item Relating the reproductive performance of westslope cutthroat trout to trait specialization to screen for artificial selection vulnerability in a conservation hatchery(Montana State University - Bozeman, College of Letters & Science, 2022) Preul-Stimetz, Taylor Nicole; Chairperson, Graduate Committee: Christine VerhilleTo mitigate westslope cutthroat trout (WCT; Oncorhynchus clarkii lewisi) declines, Montana Fish, Wildlife, & Parks carries out large scale restorations, including wild-origin stocking efforts from conservation hatcheries. Although hatcheries have made progress in limiting the effects of artificial selection on stocked populations, concerns remain that rearing practices inadvertently reduce the diversity propagated into the wild. The objective of this research was to identify traits of WCT driving poor survival or reproduction in a hatchery, allowing managers to reduce artificial selection by screening for fish requiring alternative rearing. In Chapter 1, I repeatedly measured 18 behavior, morphology, and health traits from hatchery intake (July 2019) to spawn (June 2021). I identified traits with low within- relative to between-individual variation as traits likely to be indicative of specialization. As specialists tend to maximize performance under a narrow range of conditions, they may be vulnerable to artificial selection within hatcheries. In Chapter 2, I tested whether the specialized traits identified in Chapter 1, growth rate, or age at hatchery intake of individual WCT could predict survival or reproduction. In Chapter 1, I identified nine specialized (relative condition, weighted health index, health index, body shape, energetic reserves, latency, and upper jaw, lower jaw, and anal fin residual length) traits. I hypothesized these traits would predict later survival or reproductive performance. In Chapter 2, I identified October 2019 daily growth rate in weight and every replicate length measurement after October 2019 to strongly predict total ovulated eggs and total number of hatch embryos produced by females. However, among individual variation in the median percent hatch embryos was not explained by maternal size. Male gamete quality and fertilization success was consistently high, and I found no biologically significant predictors of reproductive performance for males. I also found no predictors of survival for males or females. Despite high total ovulated eggs and total hatch embryo success for females, variable female median percent hatch embryos suggests that quality of ovulated eggs is driving current limitations to WCT hatchery reproduction. I recommend further investigation into impacts of rearing stressors and post-ovulatory aging on female WCT and their reproductive performance.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 Use of eDNA to estimate abundances of spawning Yellowstone cutthroat trout in Yellowstone National Part, Wyoming, USA(Montana State University - Bozeman, College of Letters & Science, 2020) Detjens, Colleen Rachel; Chairperson, Graduate Committee: Alexander V. ZaleInvasive Lake Trout Salvelinus namaycush and whirling disease have reduced the abundance of native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri (YCT) in Yellowstone Lake, Yellowstone National Park, thereby disrupting the Yellowstone Lake ecosystem. One indication of the YCT population decline is the decrease in the number of adults returning to tributaries to spawn each spring. Yellowstone National Park implemented a gillnetting program to remove Lake Trout starting in 1995 to restore YCT abundance and size structure and thereby conserve the Yellowstone Lake ecosystem. An important metric for evaluating the success of the program is the number of YCT ascending spawning tributaries each year. Annually, 9 to 11 of these tributaries are visually surveyed on a weekly basis from May through July for the presence of spawners, but these surveys are time consuming. The use of environmental DNA (eDNA) has become increasingly common for determining presence of aquatic species and may provide managers with a more efficient tool for estimating abundances of YCT spawners. The primary objective of my study was to evaluate the efficacy and accuracy of using eDNA to detect the presence and estimate abundance of YCT spawners by collecting eDNA samples from spawning tributaries to Yellowstone Lake in conjunction with visual surveys of YCT spawners. A secondary objective was to evaluate whether terrestrial or semi-terrestrial species such as grizzly bear Ursus arctos horribilis and North American river otter Lontra canadensis could be detected in a water sample from YCT spawning tributaries. Environmental DNA quantities were more effective for determining presence of YCT spawners than for predicting their abundances, but eDNA quantities were positively related to spawner abundances. The difference between eDNA rates when spawners are present versus absent may provide managers with an efficient method for monitoring YCT in tributaries throughout Yellowstone Lake basin. I also demonstrated that DNA from a terrestrial species, grizzly bear, can be detected in water samples. Incorporation of eDNA sampling with existing methods for monitoring YCT spawners in Yellowstone Lake tributaries would facilitate an increased scale of assessment and allow for detection and quantification of multiple species of current and future interest from single samples.Item Mechanisms of rainbow trout hybridization with native cutthroat trout in the Lamar River of Yellowstone National Park(Montana State University - Bozeman, College of Letters & Science, 2019) Heim, Kurt Conrad; Chairperson, Graduate Committee: Thomas E. McMahon; Thomas E. McMahon, Clint C. Muhlfeld, Brian D. Ertel and Todd M. Koel were co-authors of the article, 'Interspecific hybridization solves a phenological breeding mismatch for a nonnative invader' submitted to the journal 'Ecology' which is contained within this dissertation.; Thomas E. McMahon, Steven T. Kalinowski, Brian D. Ertel and Todd M. Koel were co-authors of the article, 'Invasive hybridization in a high-elevation stronghold: genetic status of Yellowstone cutthroat trout in the Lamar River of Yellowstone National Park' submitted to the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this dissertation.; Thomas E. McMahon, Brian D. Ertel and Todd M. Koel were co-authors of the article, 'Leveraging public harvest for genetic management: identification and exploitation of invasive hybrid trout in Yellowstone National Park' submitted to the journal 'Biological invasions' which is contained within this dissertation.Invasive hybridization--when invasive species interbreed with native species--is a pervasive conservation issue. Hybridization presents difficult management decisions and poses complex problems at the intersection of contemporary evolution, invasion biology, physiology, and landscape ecology. I examined the invasion scenario playing out in the Lamar River watershed of Yellowstone National Park where native Yellowstone cutthroat trout (YCT) are undergoing hybridization with introduced rainbow trout (RT). I first test the hypothesis that a breeding timing mismatch of an invasive species (i.e., RT often spawn far earlier than YCT, and eggs are scoured by snowmelt runoff) can be overcome by hybridization with a locally adapted native species, that spawn later (Chapter 2). I found support for this hypothesis. Spawning timing was strongly related to the degree of non-native admixture at the individual level, indicating that hybridization alters breeding timing in ways that could benefit hybrids. At the population level, hybrid spawning timing closely matched that of native taxa and was strongly correlated to stream flow conditions. Overall, these data suggest poorly matched spawning timing is unlikely to serve as a strong mechanism limiting invasive hybridization of YCT. Next, I mapped the spatial distribution of hybridization in the Lamar River watershed (Chapter 3). Many non-hybridized populations persist in the upper watershed, whereas a prominent source of RT in the lower watershed has likely contributed inordinately to the spread of introgression. Because hybridized populations occurred across a full range of environmental conditions, I do not predict that abiotic conditions (i.e., cold water, late-stream flow, high elevations, or small stream size) will prevent the spread of hybridization in the long-term. As such, management interventions are recommended in chapter 4 and 5. I developed a simple taxonomic key to identify hybrids and guide selective removal efforts (Chapter 4). Additionally, I used volunteer angler surveys to estimate that recreational anglers visiting the watershed (~10,000 per year) could likely harvest a substantial number of non-native trout that would contribute to genetic management goals. I conclude by providing recommendations for management and monitoring (Chapter 5).Item Feasibility of walleye population suppression in Buffalo Bill Reservoir, Wyoming(Montana State University - Bozeman, College of Letters & Science, 2019) Kaus, Daniel Joseph; Chairperson, Graduate Committee: Christopher S. GuyBuffalo Bill Reservoir, Wyoming is managed as a wild Rainbow Trout Oncorhynchus mykiss and Cutthroat Trout Oncorhynchus clarkii fishery. Nonnative Walleyes Sander vitreus were discovered in 2008, and spring sampling of Walleye indicate natural recruitment and a rapidly expanding population. Walleyes pose a predation threat to the wild trout populations in Buffalo Bill Reservoir. The Wyoming Game and Fish Department (WGFD) is interested in suppressing the Walleye population using mechanical removal with electrofishing and gillnetting during the Walleye spawning period. The purpose of this study was to evaluate the population demographics of Walleyes in Buffalo Bill Reservoir. Age-structured population models were used to estimate the Walleye population growth rate for scenarios with and without Walleye removal. To inform the population models, age-specific fecundity, probability of maturity, natural mortality, and fishing mortality were estimated. Mean asymptotic population growth rate for the five scenarios were estimated as 1.22 (95% CI of 1.05 to 1.37) for no suppression, 1.18 (95% CI of 1.04 to 1.32) for electrofish exploitation, 1.04 (95% CI of 0.88 to 1.19) for gill-net exploitation, 0.91 (95% CI of 0.61 to 1.36) for angler exploitation, and 0.81 (95% CI of 0.66 to 0.96) for angler and gill-net exploitation combined. Results from the age-structured population models suggest that long-term population suppression is a viable goal, and additional gill-net effort and angler harvest incentives should be pursued. During this study the density of mature Walleyes was low, indicating that the population had not yet reached carrying capacity. Analysis of population inertia indicates that the projected abundance of the initial population vector results in a lower population size compared to projected abundance of a population with stable-age distribution. Results from this study will be used to inform cost-effective management decisions regarding the future of the recreational fishery in Buffalo Bill Reservoir. The cost per mature female removed in 2017 was $490.91 and $80.08 for electrofish and gill net removal, respectively. Future suppression efforts should be monitored using population indices of age diversity for female Walleyes.Item Evaluation of embryo suppression methods for nonnative lake trout in Yellowstone Lake, Yellowstone National Park, Wyoming, USA(Montana State University - Bozeman, College of Letters & Science, 2019) Poole, Alex Stephen; Chairperson, Graduate Committee: Alexander V. ZaleIntroduced Lake Trout Salvelinus namaycush threaten native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in Yellowstone Lake, Yellowstone National Park. Gill nets have been used to suppress subadult and adult Lake Trout since 1995. Because survival of embryonic and larval life history stages can have profound effects on population dynamics of Lake Trout, suppression at those stages, especially if used in concert with intensive gill netting of older fish, could enhance suppression efforts. Therefore, I conducted controlled laboratory and field experiments to systematically evaluate the effects of a variety of candidate chemical (sodium chloride, calcium carbonate, gelatin, and liquid and powdered rotenone), biological (carcass and carcass analog), and physical (sediment) suppression methods on different developmental stages of Lake Trout embryos and larvae. Liquid and powdered rotenone applications, fish carcass and carcass analog exposures, and sediment deposition significantly increased embryo mortality in laboratory experiments. Sodium chloride, calcium carbonate, and gelatin applications were not effective. In-situ exposure to ground carcass material in Yellowstone Lake resulted in 100% embryo mortality in 14 and 28 kg/m 2 biomass treatments; sediment deposition caused 97% embryo mortality among overwintering incubators. Embryo mortality was probably caused by hypoxic conditions within substrates. Embryo suppression methods differed in their effectiveness, rate at which mortality was achieved, and ease of application. These differences, as well as Lake Trout spawning site characteristics such as depth, contour, fetch, substrate size, interstitial depth, isolation, and presence of non-target organisms ultimately determine which embryo suppression method will be most applicable in a given situation. Nevertheless, implementation of successful embryo suppression techniques evaluated in this study could be used to increase mortality of Lake Trout in Yellowstone Lake. Incorporating effective embryo suppression in an Integrated Pest Management approach has the potential to provide more effective Lake Trout suppression in the long term.Item Quantifying the spatial structure of invasive lake trout in Yellowstone Lake to improve suppression efficacy(Montana State University - Bozeman, College of Letters & Science, 2019) Williams, Jacob Robert; Chairperson, Graduate Committee: Christopher S. GuyConserving Yellowstone Cutthroat Trout by suppressing invasive Lake Trout in Yellowstone Lake is a high priority for Yellowstone National Park natural-resource managers. Insight into the spatial structure of Lake Trout throughout the lake will help increase the efficacy of the Lake Trout suppression program. Lake Trout (N = 578) were surgically implanted with dual acoustic and radio transmitters from 2015 through 2017. Mobile acoustic (boat) and radio (fixed-wing aircraft) telemetry surveys were performed to identify aggregations of Lake Trout. Telemetry surveys occurred during the spawning period (autumn) in 2016 and during the summer and spawning period in 2017. Lake Trout exhibited distinct aggregations during the summer and spawning period. Lake Trout aggregated at nine locations during the summer 2017 and were most frequently located in the West Thumb. Lake Trout aggregated at 22 locations during the spawning period including 12 previously undocumented putative spawning locations. Two aggregations in the West Thumb, Carrington Island and Anglers Bluff, had the highest relative densities of Lake Trout. Aggregations during the summer were generally farther from shore, greater in depth, and more dispersed than aggregations during the spawning period. Targeting locations of Lake Trout, as identified through telemetry, with gill nets was an effective strategy for increasing catch-per-unit-effort. The Lake Trout suppression program is probably altering the behavior of Lake Trout in Yellowstone Lake, which explains the high number of spawning locations and low spawning site fidelity relative to other research studies on Lake Trout spawning behavior. This study provided valuable insight into the spatial structure of Lake Trout in Yellowstone Lake. The areas Lake Trout aggregated will continue to be targeted by gillnetting and novel embryo suppression methods.Item Evaluation of suppression methods targeting non-native lake trout embryos in Yellowstone Lake, Yellowstone National Park, Wyoming, USA(Montana State University - Bozeman, College of Letters & Science, 2017) Thomas, Nathan Andrew; Chairperson, Graduate Committee: Christopher S. GuyNon-native Lake Trout Salvelinus namaycush threaten to extirpate native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in Yellowstone Lake, Yellowstone National Park. Suppression of Lake Trout in Yellowstone Lake has been ongoing since 1995, primarily by gillnetting. Unfortunately, bycatch of Yellowstone Cutthroat Trout is associated with this removal method, which targets adult and subadult Lake Trout. Alternative methods effective at causing mortality in Lake Trout early life stage(s) could be used simultaneously with gillnetting to improve suppression effectiveness. The vulnerability of salmonid embryos suggest increasing Lake Trout embryo mortality is feasible and because population growth rates are sensitive to age-0 survival an effective embryo suppression method could have population-level effects. Thus, the primary objective of this study was to evaluate the efficacy of methods to increase mortality of Lake Trout embryos. In situ experiments tested the effect of suction dredging, electroshocking, tarping, and Lake Trout carcass deposition on embryo mortality. The secondary objective of this study was to evaluate interstitial water flow using NaCl dry injection to better understand the feasibility of using chemicals for embryo suppression. Concurrent laboratory studies have shown that Lake Trout embryos experience high mortality after chemical exposure. Tarping and suction dredging were not effective at increasing embryo mortality. Electroshocking caused 0.92 mortality of embryos at the substrate surface but only 0.38 at 20 cm depth in the substrate. Lake Trout carcass deposition caused 0.99 mortality of embryos, both at the surface and at 20 cm in the substrate. The direction and rate of interstitial water flow was not consistent and future work on a larger scale is needed to inform the feasibility of chemical suppression. Hypoxic conditions within the carcass sites may have caused embryo mortality. In addition, carbon dioxide CO 2 and hydrogen sulfide H 2S are byproducts of organic matter decomposition that harm developing salmonid embryos. Embryo suppression methods are unlikely to replace traditional Lake Trout suppression methods. However, the success of Lake Trout carcass deposition shows potential for the development of an effective additional suppression method that could be implemented on a large scale.