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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 Out-migration dynamics of juvenile adfluvial bull trout in tributaries to the lower Clark Fork River, Montana(Montana State University - Bozeman, College of Letters & Science, 2021) Lewis, Madeline Collier; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Demographic characteristics and distribution of juvenile adfluvial bull trout at the tributary scale' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Seasonal capture efficiencies influences knowledge of underlying out-migration dynamics in bull trout populations with juvenile downstream trap-and-haul programs' submitted to the journal 'North American journal of fisheries management' which is contained within this thesis.; Christopher S. Guy, Eric W. Oldenburg and Thomas E. McMahon were co-authors of the article, 'Individual characteristics and abiotic factors influence outmigration dynamics of juvenile bull trout' submitted to the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this thesis.In the lower Clark Fork River, Montana, a two-way trap-and-haul program is implemented to conserve the adfluvial life-history strategy in Bull Trout Salvelinus confluentus populations in the presence of hydropower dams. We used the infrastructure in place for the program, including a permanent weir trap and multiple stationary PIT antennas, to evaluate the demographic characteristics and out-migration dynamics of juvenile bull trout, and assess the efficacy of the downstream trapping component of the trap-and-haul program. We PIT-tagged 821 juvenile Bull Trout in Graves Creek, and 144 Bull Trout in East Fork Bull River in the summer of 2019 and summer of 2020. Bull Trout in Graves Creek were primarily age 1 and age 2, with a small number of age-3 Bull Trout present (< 1%). In East Fork Bull River, age-3 Bull Trout represented 14% - 46% of the population, with a small number of age-4 and older Bull Trout present (4% - 6%). From July 2019 through December 2020, 308 tagged Bull Trout outmigrated from Graves Creek, and most out-migrants were age 2 (n = 221). In East Fork Bull River, 18 Bull Trout out-migrated, and most out-migrants were age 3 (n = 13). Capture efficiency of the permanent weir in Graves Creek varied from 83% to 100% in autumn 2019 and 2020 and was substantially lower in the spring (14%). The majority of Bull Trout out-migrated from Graves Creek during autumn 2019, spring 2020, or autumn 2020 trapping seasons (n = 276). In Graves Creek, the largest Bull Trout within the 2018 year-class were five times more likely to out-migrate at age 1 when compared to smaller fish within the cohort. The magnitude of age-1 out-migration was positively related to density. Relative changes in abiotic factors, including discharge, water temperature, and photoperiod, were cues to out-migration, and the direction of change varied by season. Understanding the demographic characteristics and outmigration dynamics of the Bull Trout in Graves Creek and East Fork Bull River enables more informed management of the trap-and-haul program and can be used to inform conservation efforts of other migratory Bull Trout populations.Item Subadult bull trout out-migration in the Thompson River drainage, Montana(Montana State University - Bozeman, College of Letters & Science, 2017) Glaid, Jeffrey Robert; Chairperson, Graduate Committee: Christopher S. GuyBull Trout populations in the Thompson River drainage have declined over the past century. Declines have been attributed to habitat fragmentation, habitat degradation, and non-native species. Out-migration characteristics (e.g., temporal and spatial origins, abiotic cues, and movement) of subadult Bull Trout (100 - 300 mm TL) were evaluated throughout the drainage to increase our understanding of local populations and better inform conservation efforts. In autumn 2014, 53 subadult Bull Trout were tagged with passive integrated transponder (PIT) tags; 29 were also surgically implanted with acoustic transmitters. Minimal Bull Trout out-migration (N = 7) was observed in 2014. In summer 2015, 566 subadult Bull Trout were PIT-tagged in the Fishtrap Creek and West Fork Thompson River drainages (Thompson River tributaries). Stream-width PIT antennas were used to monitor out-migration at the confluences of the Thompson River tributaries and at the mouth of the Thompson River. Out-migrating Bull Trout (N = 135) were sampled using directional weir traps at the tributary confluences, PIT-tagged, and implanted with acoustic- (N = 29) or radio-tags (N = 14) in autumn 2015. From July through December 2015, 10.1% of all PIT-tagged Bull Trout out-migrated from the Thompson River tributaries (11.4% of fish in the Fishtrap Creek drainage [N = 420] and 6.2% of fish in West Fork Thompson River [N = 146]), with peak out-migration occurring in late October. Highest predicted probabilities of Bull Trout out-migration occurred at lengths of 179 mm in Fishtrap Creek (30.4%) and 165 mm in West Fork Thompson River (29.3%). Only 13.5% of all Bull Trout that entered the Thompson River (N = 192) entered Thompson Falls Reservoir, with peak out-migration occurring in December. Median daily water temperature, minimum daily atmospheric pressure, and lunar illumination were weakly associated with an increase in the number of out-migrants. Radio-tagged out-migrants were randomly distributed throughout the Thompson River and exhibited long periods of site fidelity between intermittent downstream movements. Bull Trout demonstrated low out-migration rates in the Thompson River drainage and prolonged habitation of the mainstem Thompson River, which was contrary to the a priori hypothesis of clustered out-migration by subadult Bull Trout.Item Harvest, nasal-markers, and lesser scaup vital rates(Montana State University - Bozeman, College of Letters & Science, 2017) Deane, Cody Earle; Chairperson, Graduate Committee: Jay J. RotellaSince the mid-1980s, lesser scaup (Aythya affinis) population abundance has been approximately 20% below the North American Waterfowl Management Plan goal of 6.3 million lesser adult lesser scaup. Sustained harvest opportunity of this species is an important management goal in North America. We examined the relationship between harvest mortality and survival rates for a breeding population in southwest Montana from 2005 to 2016 when Adaptive Harvest Management was implemented for lesser scaup. We combined resighting, recapture, and hunter recovery to estimate survival and harvest rates using multistate capture-mark-recapture models in Program MARK. Nasal-marker loss rates were substantial and accounted for by allowing resight detection probability to decay with nasal-marker age. Adult female survival rates tended to be positively related to an interaction between annual Pacific flyway lesser scaup harvest and this value divided by the Pacific flyway daily bag limit, which we used as an index for population density (beta INTERACTION = 0.168, SE = 0.091). Estimated annual survival rates for adult metal-banded females averaged 0.66 (SE = 0.03) and 0.49 (SE = 0.02) for adult nasal-marked females, while first-winter survival rates averaged 0.39 (SE = 0.03) for metal-banded juveniles and 0.23 (SE = 0.02) for nasal-marked juveniles. However, this decrease in survival rates is not attributable to differing harvest rates between nasal-marked and metal-banded females (beta NASAL-MARKED, HARVEST RATE = 0.101, SE = 0.166). Body condition of nasal-marked females did not differ from unmarked females as their residual body mass was 1.6 g (SE = 10.4 g) less during the pre-breeding season and 3.5 g (SE = 6.5 g) less during the brood-rearing period. Nasal-marked females were found to have delayed initiating nests by 3.6 days (SE = 1.9 days) and laid 0.5 fewer eggs (SE = 0.3 eggs) relative to unmarked females while they hatched ducklings weighing 0.2 g (SE 0.2 g) more than unmarked females. Nasal-marked females were harvested 154.9 km (SE = 112.5 km) further from the study site than unmarked females, suggesting nasal-markers don't impede migration ability. Cumulatively, our results for nasal-marker impacts on vital rates suggest substantial individual heterogeneity among individuals exists in this population.Item Estimating apparent survival of sub-adult and adult white sharks (Carcharodon carcharias) in central California using mark-recapture methods(Montana State University - Bozeman, College of Letters & Science, 2013) Kanive, Paul Edward, Jr.; Chairperson, Graduate Committee: Jay J. RotellaOver-exploitation of sharks is a global conservation concern as losses of large apex predators will likely lead to negative consequences in marine ecosystems. The Northeastern Pacific white shark population is genetically distinct and geographically isolated from other known white shark populations in South Africa, Australia/New Zealand, and the Northwest Pacific. The Northeastern Pacific population/clade is comprised of two groups, Guadalupe Island, Mexico, and Central California, USA, that predictably aggregate at their respective coasts during late summer to early winter months. Recently, a three-year study using patterns on the trailing edge of dorsal fins to identify unique white sharks estimated an abundance of 219 (95% credible interval of 130 to 275) sub-adult and adult white sharks off Central California, assuming a closed population. However, there are no estimates for any of the population's vital rates (e.g. survival, recruitment rates). We use six years of mark-recapture data to estimate apparent survival and test for differences in survival between sexes for sub-adult and adult white sharks in central California. We collected 668 photographs that allowed us to identify 199 individual sharks over six years of sampling at three locations off Central California. Using a method developed by Nichols et al. (2004) that accounts for imperfect detection and imperfect sex assignment, we estimated that annual apparent survival was 0.90 (95% CI = 0.81 - 0.98) for males and females and throughout our study period. At this time, it is difficult to determine how this vital rate will affect population trend. Future research is needed to determine if this annual survival estimate is high enough for adult white sharks to produce enough offspring that will eventually recruit to the sub-adult demographic to balance annual mortality.