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Item Combination of acoustic telemetry and side-scan sonar provides insight for lake trout Salvelinus namaycush suppression in a submontane lake(Montana State University - Bozeman, College of Letters & Science, 2021) Siemiantkowski, Michael James; Chairperson, Graduate Committee: Christopher S. GuyExpansion of an invasive Lake Trout Salvelinus namaycush population in Swan Lake, Montana threatens a core area population of Bull Trout Salvelinus confluentus in Montana. Given the increased efficacy of suppression using novel embryo suppression methods, there is renewed interest in Lake Trout suppression in Swan Lake. The specific questions of this study were: 1) where are Lake Trout spawning, 2) where are the most used spawning sites, 3) what is the amount of spawning habitat, 4) does the estimated spawning area differ between estimates from telemetry locations and side-scan sonar imagery of suitable spawning substrate, and 5) how much phosphorous and nitrogen would be added to Swan Lake if carcass-analog pellet treatments were implemented? Acoustic tags were implanted in 85 Lake Trout in July and August of 2018 and 2019. Nightly tracking efforts during September, October, and November of 2018 and 2019 resulted in 1,744 relocations for 49 individual Lake Trout. Kernel-density analysis was used to evaluate Lake Trout aggregation locations identifying 10 distinct spawning sites -- corroborating previous studies. Visual observation of Lake Trout embryos confirmed spawning at three sites with the remaining seven sites considered to be unconfirmed spawning sites. All confirmed spawning sites were located in the littoral zone along areas of steep bathymetric relief and were the most used across both spawning seasons. In 2019, side-scan sonar imaging was used to classify and quantify the total area of suitable spawning substrate, which comprised 12.8% of the total surface area estimated for confirmed sites and 11.4% for unconfirmed spawning sites. Simultaneous treatment of all confirmed and unconfirmed spawning sites would require 205,709 + or - 86 kg of carcass-analog pellet material, resulting in 370.4 + or - 0.2 kg of phosphorous and 7,487.9 + or - 3.1 kg of nitrogen inputs to Swan Lake. Thus, pellet treatment would increase the Carlson's trophic state index (TSI) values from 20.8 to 27.7 for total phosphorous, and from 22.1 to 26.2 for total nitrogen. Based on a TSI threshold value of < 40 for an oligotrophic lake, the use of carcass-analog pellets could be a feasible addition to renewed Lake Trout suppression efforts in Swan Lake.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 Reproductive ecology of hatchery-origin pallid sturgeon upstream of Fort Peck Reservoir, Montana(Montana State University - Bozeman, College of Letters & Science, 2020) Cox, Tanner Lewis; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'First maturity, spawning periodicity, and follicular atresia of hatchery-origin pallid sturgeon in the Missouri River above Fort Peck Reservoir, Montana' submitted to the journal 'Journal of applied ichthyology' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Reproductive ecology and behavior of hatchery-origin pallid sturgeon in the Missouri River above Fort Peck Reservoir, Montana' submitted to the journal 'Journal of applied ichthyology' which is contained within this thesis.Conservation propagation of pallid sturgeon above Fort Peck Reservoir has successfully recruited a new generation of spawning-capable pallid sturgeon to a location that would otherwise have fewer than 30 remaining. Successful recovery of pallid sturgeon will now rely on spawning in locations that provide adequate drift distance for larvae to recruit. Prior to this study, all reproductively-active female pallid sturgeon underwent ovarian follicular atresia. The reasons for and prevalence of ovarian follicular atresia were unclear, spawning periodicity of females remained undescribed, and remaining prepubescent fish indicated that age- and size-at-first maturity would vary more than currently described. Furthermore, spawning location, spawning-related interactions among conspecifics, and substrate composition at spawning locations remained undescribed. We used data on reproductive status and location to describe age- and size-at-first maturity, the prevalence of ovarian follicular atresia during first gametogenic cycles, spawning periodicity for female and male pallid sturgeon, where spawning occurs, if spawning locations are related to discharge, if substrate characteristics at the spawning locations were similar to other river reaches, and if female, male, and atretic female pallid sturgeon use the river similarly. Pallid sturgeon matured at older ages and larger sizes than described for other populations with females maturing at 18 years old and males at 15; however, prepubescent pallid sturgeon as old as 20 were documented. During the presumed-first gametogenic cycle, 62.5% of female pallid sturgeon underwent follicular atresia. Females had biennial reproductive cycles, and males had annual and biennial reproductive cycles. Reproductively-active male and female pallid sturgeon were found in similar locations, while locations of atretic female pallid sturgeon varied. The furthest upstream locations of pallid sturgeon including locations in the Marias River occurred during 2018 when discharge was at an unprecedented high. Spawning occurred in locations less than 131 km from the river-reservoir transition zone, which does not provide adequate drift-distance for larvae. Altering discharge and water temperature at Tiber Dam to mimic observed values in 2018 may increase use of the Marias River by pallid sturgeon during spawning, which would provide adequate drift distance to larvae.Item Movement of Scaphirhynchus species in the Missouri River above Fort Peck Reservoir, Montana(Montana State University - Bozeman, College of Letters & Science, 2011) Richards, Ryan Roy; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy and William M. Gardner were co-authors of the article, 'Movements of Scaphirhynchus Spp. in the upper Missouri River' in the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Christopher S. Guy, Molly A. Webb, William M. Gardner and Casey B. Jensen were co-authors of the article, 'Spawning related migration of shovelnose sturgeon in the Missouri River above Fort Peck Reservoir, Montana' in the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.Some Scaphirhynchus spp. populations are endangered, in decline or extirpated. Operation of dams and reservoirs on the Missouri River has been implicated in declines in Scaphirhynchus spp. abundance. It is hypothesized that discharge from dams upstream of Scaphirhynchus spp. populations are insufficient to provide the environmental cue initiating spawning migrations. The goal of this thesis was to investigate the effects of variations in spring discharge on movements of Scaphirhynchus spp. in the Missouri River above Fort Peck Reservoir. A secondary goal was to provide information on the distribution of Scaphirhynchus spp. locations relative to larval drift distance. Twenty-four hatchery-reared juvenile pallid sturgeon, seven adult pallid sturgeon, and 192 shovelnose sturgeon were tracked from 2006 through 2009 and movements were compared among years with hydrologic conditions from above to below average discharge. Seventy-eight shovelnose sturgeon in five reproductive categories (i.e., males, confirmed spawning females, potentially spawning females, atretic females, and reproductively inactive females) were tracked in 2008 and 2009. Movements were compared among all reproductive categories within years and between years for confirmed spawning females while integrating the environmental effects of discharge and water temperature. The majority of pallid sturgeon locations in all years were within 75 km of the headwaters of Fort Peck Reservoir. Shovelnose sturgeon locations were distributed across the entire study reach, and were 100 km further upstream than pallid sturgeon locations. Based on current estimates, an insufficient length of river exists upstream of the Fort Peck Reservoir headwaters for pallid sturgeon larval drift. Movement rates of Scaphirhynchus spp. did not differ among years 2006-2009, and movements did not differ between years for confirmed spawning female shovelnose sturgeon 2008-2009, indicating that discharge did not influence movements. At the conditions in this study, movement rates of confirmed spawning female shovelnose sturgeon were highest at water temperatures suitable for spawning regardless of discharge, providing support for the hypothesis that water temperature rather than discharge is a more likely proximate cue initiating spawning migrations in Scaphirhynchus spp.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.Item Spawning and early life-history characteristics of bull trout in a headwater-lake ecosystem(Montana State University - Bozeman, College of Letters & Science, 2010) Tennant, Lora Beth; Chairperson, Graduate Committee: Christopher S. Guy; Robert E. Gresswell (co-chair)Bull trout, Salvelinus confluentus, are in decline throughout their native range. Interaction with nonnative species is considered to be one of the drivers of bull trout decline. Bull trout exhibit a variety of life-history strategies and lacustrine-adfluvial bull trout seem to be particularly susceptible to population decline when nonnative lake trout, S. namaycush, invade or are introduced into lakes where bull trout are the dominant salmonid. Quartz Lake in Glacier National Park, Montana, provided a unique opportunity to gather information on the spawning and early life-history characteristics of a bull trout population prior to anticipated declines in bull trout abundance due to lake trout invasion. The objectives of this study were (1) to characterize the spatial and temporal dynamics of bull trout spawning migrations and associate areas of high redd accumulation to abiotic factors, and (2) to quantify the influence of abiotic factors on the distribution of subadult bull trout in tributary streams of Quartz Lake. Stream surveys were conducted to quantify physical habitat characteristics in the study area, backpack electrofishing was used to sample subadult bull trout rearing in lake tributaries, and redd surveys were used to investigate the spatial and temporal trends in the accumulation of bull trout redds. Bull trout redds and subadult bull trout were found throughout the study area; however, bull trout spawning and rearing appeared to be concentrated in lower Quartz Creek. This area was low gradient, and there was a high percent of gravel and cobble substrates. Bull trout spawning began in late September, peaked in early October, and concluded in mid-October. These data provide important information on bull trout life-history in headwater lakes and provide biologists with baseline data that will be useful for assessing the effects of lake trout suppression efforts that began in 2009.