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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 Spatial and temporal variability in movements and vital rates of sympatric salmonids in an unfragmented, inland watershed(Montana State University - Bozeman, College of Letters & Science, 2019) Lance, Michael James; Chairperson, Graduate Committee: Alexander V. ZaleThe life history patterns and vital rates of stream dwelling fish can differ across biological, spatial, and temporal scales. We determined the movement patterns and vital rates of three abundant salmonids--brown trout (Salmo trutta), mountain whitefish (Prosopium williamsoni), and rainbow trout (Oncorhynchus mykiss)--in the Smith River watershed of Montana, a system with three distinct geomorphic regions: the headwaters, semi-wilderness canyon, and prairie. We marked 7,172 fish with passive integrated transponder (PIT) tags, monitored their watershed-scale movements past 15 stationary PIT arrays over four years, and relocated fish between arrays by conducting mobile surveys along the Smith River and major tributaries. Fish movement patterns and survival probabilities varied seasonally, among species, and among locations within the watershed. Volume of movement and diversity of movers were both greatest in the canyon region and in lower portions of tributaries. Fish rarely left the canyon, but movement into the canyon from other regions was common among some groups of fish. Mountain whitefish were most likely to move and brown trout were least likely to move. The stream lengths traversed by fish followed a leptokurtic distribution with most fish travelling < 10 km and decreasing numbers of fish travelling farther. Distinct life history patterns were not evident as judged by the stream lengths traversed by tagged fish; rather, a continuous spectrum of distances traversed was apparent. Species-specific spawning periods were associated with increased frequency of movement by mountain whitefish and rainbow trout. Increases in the frequency of watershed-scale movements of all three species were associated mean daily water temperatures of 11.7-15.3°C, compared to periods when water temperatures were cooler or warmer. Annual probabilities of survival were highest among mountain whitefish (0.38-0.54) and lower among brown trout (0.16-0.38) and rainbow trout (0.08-0.39). Survival of rainbow trout and mountain whitefish was highest in the canyon. Survival of mountain whitefish was also high in the headwaters but was lowest in the prairie. Movements of fish in the Smith River watershed were diverse, allowed movement among habitats with different probabilities of survival, and probably contributed to meta-population function, population resiliency, and species diversity.Item The influences of diet and water systems on rainbow trout gut microbiome in relation to nutrient utilization(Montana State University - Bozeman, College of Agriculture, 2017) Betiku, Omolola Comfort; Chairperson, Graduate Committee: Carl Yeoman; T. Gibson Gaylord and Wendy M. Sealey were co-authors of the article, 'Evaluation of protein reduction and essential amino acids supplementation of plant- and animal protein-based diets on production of rainbow trout (Oncorhynchus mykiss)' submitted to the journal 'Journal of the World Aquaculture Society' which is contained within this thesis.; Carl J. Yeoman, T. Gibson Gaylord, Suzanne L. Ishaq, Glenn C. Duff, Aurelien Mazurie and Wendy M. Sealey were co-authors of the article, 'Divided nutritive function of the rainbow trout (Oncorhynchus mykiss) mid- and hind- gut microbiomes' submitted to the journal 'Frontiers in microbiology' which is contained within this thesis.; Carl J. Yeoman, T. Gibson Gaylord, Glenn C. Duff, Brian Bothner, Stephanie S. Block and Wendy M. Sealey were co-authors of the article, 'Differences in amino acid catabolism by gut microbes with/without prebiotics inclusion in GDDY-based diet affect feed utilization in rainbow trout' submitted to the journal 'Aquaculture' which is contained within this thesis.; Carl J. Yeoman, T. Gibson Gaylord, Ben Americus, Sarah Olivo, Glenn C. Duff and Wendy M. Sealey were co-authors of the article, 'Water system is a controlling variable modulating bacterial diversity of gastrointestinal tract and performance in rainbow trout' submitted to the journal 'Plos one' which is contained within this thesis.Plant protein ingredients are sustainable sources of protein that could be used to meet the demand of the growing aquaculture industry. However, feeding plant protein diets has some drawbacks in terms of reduced growth and poor feed efficiency. This dissertation evaluated the production cost of alternative protein diets for commercial production of rainbow trout. Also, it identified the microbiota and gene functions associated with alternative diets and how they differ between mid- and hind-gut sections of the rainbow trout intestine. Furthermore, it determined differences in microbial community compositions and functions in the luminal and mucosal GIT of trout when fed alternative diets, with/without prebiotics. Lastly, the significance of diet and water as environmental factors shaping the mucosal and luminal bacterial compositions in trout was investigated. Experiment 1 demonstrated that trout growth and body indices were not affected by feeding plant protein diet (PPD). In experiment 2, shotgun metagenomics revealed predominant bacterial population in trout microbiota. Genes related to carbohydrate metabolism were increased in the hindgut intestine of those fed PPD. Experiment 3 demonstrated that replacing fishmeal with 75% GDDY did not alter growth of trout, but not feed intake and feed conversion ratio (FCR). High inclusion of GDDY in trout diet resulted in enrichment of catabolic genes involving branched chain amino acids in trout midgut region. Experiment 4 showed that rearing in a recirculating water system significantly improved trout performance compared to rearing in a flow-through water system, while feed intake and FCR increased in fish raised in the flow-through system. Water samples were more diverse than GIT samples. Bacterial diversity was greater in mucosal scrapings of the GIT than in the lumen. Water system played a major role influencing the microbial communities in trout luminal and mucosal GIT. The lumen shared similar bacteria with the rearing water. The results of this study demonstrated that plant protein can effectively substitute for fishmeal in trout diets. It further showed that trout GIT microbiota vary between the mid- and hind-GIT. The hind-, but not the mid-GIT microbiome appears to be modulated by diet, while the mid-GIT is affected by water system.Item The spawning and rearing habitats of rainbow trout and brown trout in two rivers in Montana(Montana State University - Bozeman, College of Letters & Science, 1981) Sando, Steven KentItem Diet overlap and habitat utilization of rainbow trout and juvenile walleye in Cooney Reservoir, Montana(Montana State University - Bozeman, College of Letters & Science, 1994) Venditti, David AllanItem Responses of rainbow (Oncorhynchus mykiss) and brown trout (Salmo trutta) to creation of access into a spawning tributary(Montana State University - Bozeman, College of Letters & Science, 1996) Snelson, Scott IrvenItem Potential impacts of altering discharge pattern from Hauser Dam, Missouri River, on young-of-the-year brown trout and rainbow trout(Montana State University - Bozeman, College of Letters & Science, 1985) Carty, Daniel GregoryDaily flow fluctuations would occur in the Missouri River between Hauser Dam and Holter Reservoir if Hauser Dam were converted to a hydroelectric peaking facility. To address potential impacts of fluctuating flows on free-swimming young-of-the-year (YOY) brown trout (Salmo trutta) and rainbow trout (S. gairdneri) emergence, growth, abundance, distribtion, movement, and habitat use were investigated. During reduced-flow tests stranding, isolation, displacement, and habitat changes were evaluated. Hydraulic modeling was used to predict changes in the quantity of usable habitat at different discharges. Recruitment from a tributary into the river was also monitored. Field data were collected between April 1982 and November 1983. Young-of-the-year brown trout were first observed in early April while YOY rainbow trout were first found in mid-June. Both species used relatively shallow, low-velocity water near shore where cover was abundant. Reduced-flow tests in August of each year revealed little stranding or isolation, and YOY trout were not permanently displaced from temporarily dewatered habitat. Hydraulic modeling predicted an increase in the quantity of habitat as discharge decreased, but field observations indicated a reduction in habitat quality. The tributary was found to be a relatively important source of recruitment to the river rainbow trout fishery but rather unimportant to the river brown trout fishery.Item Cellular inflammatory response of rainbow trout to PKX(Montana State University - Bozeman, College of Agriculture, 1988) MacConnell, ElizabethItem Effects of gas supersaturated water on juvenile brown and rainbow trout(Montana State University - Bozeman, College of Letters & Science, 1988) Connor, William PaulSix bioassays were conducted at the Bozeman Fish Technology Center using juvenile brown trout (Salmo trutta) and rainbow trout (Salmo gairdneri) to determine the influence of fish size and species to gas supersaturated water. Juveniles of both species were exposed for 30-d to 104 + 1.2% (control), 112 ± 1.0% (medium treatment), and 125 + 0.7% (high treatment) atmospheric gas supersaturated water. No significant mortality occurred in the 112% treatment except during two tests when percent total gas pressure exceeded 113%, indicating that a critical threshold exists above this pressure. As fish grew they became more susceptible to 125% gas supersaturation. Total mortality and mortality rate were less when fish were small. The frequency at which emphysema occurred by body region also varied with fish size and smaller fish died with different external symptoms than larger fish. Larger fish were more likely to die faster than smaller fish and with no external symptoms. Daily mortality of brown trout exposed to 125% gas supersaturation was always significantly greater than for rainbow trout of similar size. Juvenile brown trout that survived exposure to 112% supersaturation showed greater incidence of external symptoms of GBT than juvenile rainbow trout of similar size. Juvenile rainbow and brown trout were exposed to supersaturations from 112% -118% total gas pressure to test for recovery. Recovery varied according to external symptom severity. Fish that did not recover usually had severe exopthalmia. Juvenile brown trout, repeatedly exposed to 118% gas supersaturated water, given 30-d to recover between exposures, developed more severe symptoms with each exposure. Sublethal effects of exposure to gas supersaturated water on growth, predation, and microbial infection were tested using fish exposed to supersaturations from 112 - 118% total gas pressure. Surviving fish developed new symptoms more often than recurring symptoms. Growth of survivors of 30-d exposure to 112% total gas pressure was not different from control fish. There was no difference in vulnerability to predation in circular tanks between juvenile brown and rainbow trout caused by exposure to gas super-saturation. Predation tests conducted in an artificial stream suggested some difference in susceptibility may be present, but data were not conclusive. Bacterial challenges indicated that juvenile brown trout exposed to 118% gas supersaturated water for 5-d were more susceptible to infection by Aeromonas hvdrophila than non-exposed fish.