Theses and Dissertations at Montana State University (MSU)
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Item Life history characteristics and the effects of climate on growth of Yellowstone cutthroat trout in headwater basins(Montana State University - Bozeman, College of Letters & Science, 2015) Uthe, Patrick Ryan; Chairperson, Graduate Committee: Alexander V. Zale; Robert Al-Chokhachy, Alexander Zale and Bradley Shepard were co-authors of the article, 'Life history characteristics and vital rates of Yellowstone cutthroat trout in two headwater basins' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Robert Al-Chokhachy, Bradley Shepard, Alexander Zale and Jeffrey L. Kershner were co-authors of the article, 'Effects of climate-driven stream factors on summer growth patterns of Yellowstone cutthroat trout' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.The Yellowstone Cutthroat Trout was historically distributed throughout the Upper Yellowstone and Upper Snake River drainages, but now occupies only 42% of its original range because of habitat degradation and introduced salmonid species. Many of the current strongholds are located on public land in mountainous watersheds with low human disturbance. However, knowledge of life history characteristics of headwater populations is limited. Moreover, streams throughout the Rocky Mountains have already exhibited symptoms of climate change through alterations in thermal and hydrologic regimes, but it is unknown how these changes will affect fish populations. To address these needs, we implemented a mark-recapture study on five populations of trout from Spread Creek, Wyoming, and Shields River, Montana, to estimate annual growth, survival rates, and movement patterns, and document the effects of discharge, temperature, and food availability on summer growth patterns. Survival rates were high compared to survival rates of other Cutthroat Trout subspecies and large trout generally had lower survival rates than small trout. Downstream movements out of streams by tagged trout were substantial. Annual growth rates varied among streams and size classes, but were relatively low compared to populations of Yellowstone Cutthroat Trout from large, low elevation streams. Trout grew more in length than weight in summer, suggesting an investment in structural growth rather than accumulation of reserve tissues. Temperature and discharge had strong effects on summer growth, but the effect of discharge was greater for growth in weight than in length, probably resulting from increased prey availability at high discharges. Temperature interacted with fish length such that small trout responded favorably to increased average daily temperatures near physiological optima and increased growing season length, whereas large trout responded negatively to warming temperatures. These estimates of key demographic parameters are useful in developing management and conservation strategies. Additionally, we documented that even under thermally suitable conditions, discharge can have significant effects on growth, making it important to consider multiple factors affected by climate change when devising climate adaptation strategies for coldwater fishes.Item Dynamics of Yellowstone cutthroat trout and lake trout in the Yellowstone Lake ecosystem : a case study for the ecology and management of non-native fishes(Montana State University - Bozeman, College of Letters & Science, 2015) Syslo, John Michael; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy and Todd M. Koel were co-authors of the article, 'Trophic overlap and temporal diet shifts for a nonnative and a native salmonid in Yellowstone Lake, Yellowstone National Park' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Christopher S. Guy, Todd M. Koel, Patricia E. Bigelow, Philip D. Doepke, Brian D. Ertel and Jeffrey L. Arnold were co-authors of the article, 'Response of Yellowstone cutthroat trout to suppression of non-native lake trout in the Yellowstone Lake ecosystem' submitted to the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this thesis.The introduction of lake trout Salvelinus namaycush into Yellowstone Lake preceded the collapse of the native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri population. As a system with a simple fish assemblage and several long-term data sets, Yellowstone Lake provided a unique opportunity to evaluate the ecology of a native salmonid in the presence of a non-native salmonid population undergoing suppression in a large natural lake. Diet data for Yellowstone cutthroat trout and lake trout were evaluated at varying densities to determine the effects of density on diet composition. Temporal diet shifts from 1996-1999 to 2011-2013 were likely caused by limitation of prey fish for lake trout. Diets, stable isotopes, and depth-related patterns in CPUE indicated lake trout > 300 mm consumed primarily amphipods, making them trophically similar to Yellowstone cutthroat trout from during 2011-2013. A lake trout removal program was initiated during 1995 to reduce predation on Yellowstone cutthroat trout. Abundance and fishing mortality were estimated for lake trout from 1998 through 2013 and Yellowstone cutthroat trout from 1986 through 2013. Density-dependence was evaluated by examining individual growth, weight, maturity, and pre-recruit survival as a function of abundance. In addition, a simulation model was developed for the lake trout- Yellowstone cutthroat trout system to determine the probability of Yellowstone cutthroat trout abundance persisting at performance metrics given potential reductions in lake trout abundance. Estimates of Yellowstone cutthroat trout abundance varied 5-fold and lake trout abundance varied 6-fold. Yellowstone cutthroat trout weight and pre-recruit survival decreased with increasing Yellowstone cutthroat trout abundance; however, individual growth and maturity were not related to abundance. Lake trout population metrics did not vary with lake trout abundance. Simulation model results were variable because of uncertainty in lake trout pre-recruit survival. Conservative estimates for required lake trout reductions were > 97% of 2013 abundance for a > 70% probability of Yellowstone cutthroat trout persistence at the performance metrics outlined in the Native Fish Conservation Plan. Lake trout removal will likely reduce lake trout abundance and result in Yellowstone cutthroat trout recovery if the amount of fishing effort exerted in 2013 is maintained for at least 15 years.Item Relative contributions of climate variation, lake trout predation, and other factors to the decline of Yellowstone Lake cutthroat trout during the three recent decades(Montana State University - Bozeman, College of Letters & Science, 2010) Kaeding, Lynn Robert; Chairperson, Graduate Committee: Daniel Goodman; Thomas E. McMahon (co-chair)The relative contributions of climate variation, lake trout Salvelinus namaycush predation, and other factors to the recent, three-decade decline of the lacustrine-adfluvial (i.e., a life-history form consisting of fish that mostly live in a lake but spawn in an inflowing tributary) Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri (YCT) population of Clear Creek, a Yellowstone Lake tributary, were evaluated. Strong growth of that population's storied spawning run between the early 1960s and 1978, when the run peaked at about 70,000 fish, had been considered key evidence of recovery of the lake's YCT population from formerly excessive angler harvest and other adverse factors. Thus the run's subsequent, almost continuous decline to about 500 fish in 2007 was perplexing. Gillnet catches of YCT at established lake locations likewise indicated a concurrent decline in the lake-wide YCT population. Prominent among the factors that may have importantly affected the YCT population during the recent decades was predation by the illegally introduced, reproducing, nonnative lake trout discovered in Yellowstone Lake in 1994. Data mainly taken from YCT in the spawning run (n = 29 years) and gillnet catch (n = 30 years) were examined for information useful to specifying the Leslie matrix of a dynamic, age-structured model that had climate as a covariate. The model, fitted to spawning run size and mean total length (TL) of YCT in the run during 1977-2007 (n = 29 data years), explained 87% of variation in observed run size, 86% of variation in observed mean TL, and strongly suggested that climate (as indexed by total-annual air degree-days > 0°C measured on the lake's north shore) had an important effect on recruitment of age-0 YCT to subsequent spawning runs. Results also suggested that an effect of lake trout predation on survival of age-1 to age-5 YCT became apparent only during the recent decade. The important test of ongoing efforts to control lake trout in Yellowstone Lake and thereby limit their predation on YCT - on the basis of data for YCT - will occur when climatic conditions improve for YCT recruitment to the Clear Creek and other YCT spawning stocks of the lake.Item Influence of environmental features on Tubifex tubifex and Myxobolus cerebralis infected Tubifex tubifex in Yellowstone National Park : implications for whirling disease risk(Montana State University - Bozeman, College of Letters & Science, 2010) Alexander, Julie Diane; Chairperson, Graduate Committee: Billie L. KeransWhirling disease (WD) is an emerging parasitic disease of salmonids that is increasing in severity and geographic range. Whirling disease is caused by the myxosporean parasite, Myxobolus cerebralis, and can effect significant mortality in wild and cultured salmonid populations. Myxobolus cerebralis was recently detected in Yellowstone National Park (YNP) where it may be causing native Yellowstone cutthroat trout (YCT) to decline. Myxobolus cerebralis exploits the aquatic oligochaete, Tubifex tubifex, as its primary host and spores released by T. tubifex are infective to salmonid fish. The aim of this study was to assess WD risk for YCT populations in YNP by focusing on the disease source, T. tubifex, which had not previously been characterized. My objectives were to characterize T. tubifex populations and dynamics of M. cerebralis infections in T. tubifex and to establish factors associated with M. cerebralis infections in T. tubifex. In addition, I examined relationships between infection dynamics in T. tubifex and transmission to fish hosts (WD risk). In Pelican Creek, T. tubifex and M. cerebralis infected T. tubifex were widely distributed and abundant. Infected T. tubifex were most abundant in reaches characterized by intermediate geothermal influence. However, WD risk was high in all reach types, which indicated that low parasite success in the oligochaete host in reaches with high or no geothermal influence did not translate into reduced WD risk in these reaches. In tributaries throughout YNP, susceptible T. tubifex were widely distributed but experimental and field data suggest M. cerebralis-infected T. tubifex may be unable to survive in all tributaries where uninfected T. tubifex were found. In particular, environmental factors influenced by confinement, including proportions of coarse and fine substrates, may preclude establishment of M. cerebralis in tributaries in YNP. Thus, environmental features, rather than oligochaete host factors, may be most influential for M. cerebralis dynamics in T. tubifex and WD risk to fish in YNP. While further research is needed to identify specific mechanisms, these results suggest environmental features related to confinement may be useful for assessing WD risk at broad scales when the oligochaete host is characterized by low genetic variability.Item Myxobolus cerebralis in native Cutthroat trout of three spawning tributaries to Yellowstone Lake : a qualitative ecological risk assessment(Montana State University - Bozeman, College of Letters & Science, 2008) Murcia, Silvia; Chairperson, Graduate Committee: Billie L. Kerans; Todd M. Koel (co-chair)Most environments impose periodic or stochastic stress on natural populations, which increase susceptibility to diseases. Infection by Myxobolus cerebralis (exotic parasite causing salmonid whirling disease) is strongly influenced by a stream's physicochemical attributes and stressors, which may also affect host pathology. Susceptibility to M. cerebralis varies greatly among different species and subspecies of the salmonid host, but little is known about lesion severity or location of infection among the native Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri). In 2002 and 2003 we performed a series of 10-day sentinel cutthroat fry exposures and habitat assessments in various sites of three M. cerebralis-positive tributaries to Yellowstone Lake: the Yellowstone River, Pelican Creek, and Clear Creek. At 90 and 150 days post-exposure, fry were examined by polymerase chain reaction and histology to determine prevalence, severity, and location of infection. The goal was to identify spatiotemporal patterns of infection, and physicochemical features of the streams influencing it, and potentially facilitating parasite invasion and establishment. Results on fish (young and adult) host infection data, environmental attributes, and tubificid host presence/absence data in the study streams were used to develop an ecological risk assessment for parasite establishment and whirling disease in this ecosystem. Results from our qualitative risk ranking systems suggest that the cutthroat trout of the Yellowstone Lake basin are highly susceptible to M. cerebralis infection, with the most severe lesions in cartilage of the cranium and jaws, especially in systems with high water temperatures and ionic content. Our results also suggest that such environmental features are most conducive to parasite establishment, especially in tributaries of the lake basin used by cutthroat trout as spawning and rearing habitats. Thus, this study has implications for both ecology and parasitology as it reveals that environmental components can affect when and where a pathogen resides within the host, and thereby affect manifestation of disease. Recognition of the specific environmental attributes most conducive to parasite establishment, and disease, can increase future diagnostics, detection, and management efforts, strengthening the likelihood of correctly predicting M. cerebralis' and similar pathogenic invasions and establishment in unsampled sites.Item Assessment of reproductive isolation between Yellowstone cutthroat trout and rainbow trout in the Yellowstone River, Montana(Montana State University - Bozeman, College of Letters & Science, 2004) De Rito, Jr., James Nicholas; Chairperson, Graduate Committee: Alexander V. ZaleThe genomic extinction of Yellowstone cutthroat trout (Oncorynchus clarki bouvieri) has occurred throughout many parts of its historic range because of displacement and introgression with introduced rainbow trout (O. mykiss). However, fluvial cutthroat trout still retain their genetic integrity while co-existing with rainbow trout in the Yellowstone River drainage, Montana. I assessed whether spatial or temporal reproductive isolation, or both, occurs between these taxa. Time and place of spawning was determined by radio-telemetry of a total of 164 trout (98 cutthroat, 37 rainbow, and 29 cutthroat x rainbow hybrids) over three spawning seasons, from 2001 to 2003. Fish were telemetered in four areas of a 140-km segment of the mainstem Yellowstone River. Of the 164 radio-tagged fish, 73 (44 cutthroat trout, 15 rainbow trout, and 14 hybrids) were assumed to have spawned. Fifty-five (75.3%) of 73 radio-tagged fish that spawned used 16 tributaries, 17 (23.3%) used 7 river side channels, and 1 (1.4%) used the main channel of the Yellowstone River. The majority of fish that spawned (62%) used five spawning areas. These were used by 79% (N = 11) of hybrids, 61% (N = 27) of cutthroat trout, and 47% (N = 7) of rainbow trout that spawned. Spawning-area and spawning-reach overlap index values were high among all taxa. In contrast, mean migration and spawning dates of rainbow trout and hybrids were 5 to 9 weeks earlier than of cutthroat trout. Rainbow trout and hybrids began migrating and spawning in April and May when Yellowstone River discharges were lower and water temperatures were colder than discharges and temperatures during cutthroat trout migration and spawning in June and July. Spawningperiod overlap index values between rainbow trout and hybrids versus cutthroat trout were typically less than half the spatial overlap index values. Therefore, difference in time of spawning is likely the predominant mechanism eliciting reproductive isolation. Management actions focused on later spawning cutthroat trout in tributaries may enhance temporal reproductive isolation from rainbow trout and hybrids.