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Item Attraction, entrance, and passage efficiency of arctic grayling, trout, and suckers at Denil fishways in the Big Hole River Basin, Montana(Montana State University - Bozeman, College of Letters & Science, 2020) Triano, Benjamin Louis; Chairperson, Graduate Committee: Thomas E. McMahonThe Big Hole River in southwest Montana supports the only indigenous, self-sustaining fluvial population of Arctic Grayling (Thymallus arcticus) in the conterminous United States. Denil fishways have been installed at 63 low-head irrigation diversion dams throughout the basin to provide grayling and other fishes year-round access to critical habitats; however, their efficiency has not been evaluated comprehensively. We quantified attraction, entrance, and passage efficiency of grayling, trout (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta), and suckers (White Sucker Catostomus commersonii and Longnose Sucker C. catostomus) at six Denil fishways during 14 trials conducted over a range of fishway slopes and hydraulic conditions. Tagged hatchery-reared grayling and wild fish of several taxa were released downstream of diversions in each trial, and upstream passage was monitored for 72 hours using passive integrated transponder telemetry. Attraction (60.4-84.3%) and entrance (44.3-78.6%) efficiencies limited overall fishway efficiencies (19.1-55.8%), but passage efficiencies (96.2-97.0%) were high for all taxa over all conditions tested. Attraction of hatchery-reared grayling was limited at fishways with shallow upstream depths (low fishway discharges) and low attraction flows, but wild trout and suckers were less limited by these effects. Entrance of grayling and trout was limited at high fishway discharges and fishways with steep slopes, but both species groups were more likely to enter fishways with deep downstream depths than those with shallow downstream depths. Entrance appeared to be limited by turbulent plunging conditions associated with shallow downstream depths. Denil fishways demonstrated great promise for improving habitat connectivity for grayling and other fishes in the Big Hole River basin; however, attraction and entrance were key bottlenecks that limited overall fishway efficiency. Maintaining high attraction flows and deep downstream depths should be the focus of adaptive management strategies and design criteria to improve overall efficiency of Denil fishways in the Big Hole basin.Item Comparative morphology and host-parasite studies of Trichophyra clarki (N.Sp.) on cutthroat trout (Salmo clarki)(Montana State University - Bozeman, College of Agriculture, 1969) Heckmann, Richard AndersonItem Homing and orientation of cutthroat trout (Salmo clarki) in Yellowstone Lake, with special reference to olfaction and vision(Montana State University - Bozeman, College of Agriculture, 1967) McCleave, James DavidItem The life cycle of Cotylurus erraticus (Rudolphi, 1809) Szidat, 1928 (Trematoda: Strigeidae) and the effect of the metacercaria on rainbow trout (Salmo gairdneri)(Montana State University - Bozeman, College of Agriculture, 1968) Olson, Robert EldonItem Movement and homing of cutthroat trout (Salmo clarki) in Bridge and Clear creeks, Yellowstone National Park(Montana State University - Bozeman, College of Agriculture, 1970) LaBar, George WilliamItem Limiting factors for trout populations in the upper Clark Fork River superfund site, Montana(Montana State University - Bozeman, College of Letters & Science, 2013) Mayfield, Mariah Pine; Chairperson, Graduate Committee: Thomas E. McMahonLarge-scale heavy metal contamination of the upper Clark Fork River from mining deposits has created significant damage to aquatic habitat in the drainage. Trout are present in the system, although with abundances lower than expected. The objectives of this study were to identify critical habitat areas and to identify conditions that continue to limit both native and nonnative trout populations, with the focus of the study on the lingering environmental effects caused by high heavy metal concentrations. A radiotelemetry study, with 256 tagged brown trout Salmo trutta, westslope cutthroat trout Oncorhynchus clarkii lewisi, and cutthroat/rainbow hybrid trout, was conducted from 2009 to 2011. The radiotelemetry relocation data was used to determine temporal and spatial patterns in movement and survival rates in relation to heavy metals and other environmental factors, and to identify critical habitat areas (e.g., spawning locations and overwintering areas). Brown trout spawning occurred in numerous tributaries throughout the basin and in the upper reaches of the mainstem. Cutthroat trout spawned only in tributaries, and these tributaries were often smaller and more degraded by land use practices than brown trout spawning tributaries. Multistate mark-recapture survival analysis estimated that survival is lowest in the stream segment with the greatest amount of heavy metal contamination; the weekly likelihood of survival was estimated at 0.97 (95% confidence interval 0.97 - 0.98) for brown trout and 0.90 (95% confidence interval 0.84 - 0.97) for cutthroat trout. Additionally, weekly survival estimates for cutthroat trout in tributaries was also low (0.92; 95% confidence interval 0.87 - 0.94), likely because of anthropogenic land use pressures. Very limited movement was observed, except in relation to spawning migrations. Cutthroat trout moved greater distances and at a higher rate than brown trout. The results from this study indicate that the remaining mining contamination continues to reduce trout survival rates throughout the basin and should be removed in order to increase trout densities. Additionally, restoration priority should be placed on tributaries that are negatively affected by land use pressures.