Browsing by Author "Bestgen, Kevin, committee member"

Now showing 1 - 5 of 5

Open Access
Investigating the direct and indirect effects of introduced greenback cutthroat trout on boreal toad recruitment
(Colorado State University. Libraries, 2015) Lanier, Wendy Elizabeth, author; Bailey, Larissa, advisor; Bestgen, Kevin, committee member; Funk, Chris, committee member
To view the abstract, please see the full text of the document.
Open Access
Jumping and swimming performance of burbot and white sucker: implications for barrier design
(Colorado State University. Libraries, 2014) Gardunio, Eric, author; Myrick, Christopher, advisor; Bestgen, Kevin, committee member; Hooten, Mevin, committee member; Bledsoe, Brian, committee member; Zafft, David, committee member
Chapter 1 - Illegally introduced burbot (Lota lota) populations have spread throughout the Green River drainage (GRD) of the upper Colorado River Basin in Wyoming and Utah, USA where they are having adverse effects on native and sport fisheries. We analyzed existing data to evaluate the status of burbot in southwestern Wyoming. Burbot appear to have been illegally introduced into Big Sandy Reservoir in the early- to mid-1990's, based on capture of burbot in 2003 that included one 16 year old fish and several between 7 and 12 years of age. Burbot began expanding throughout the Green River Drainage in the early 2000s and, with the assistance of a secondary introduction into Fontenelle Reservoir, have successfully invaded most portions of the GRD upstream of the Flaming Gorge Dam. Only one burbot has been captured downstream of Flaming Gorge Reservoir, but this detection indicates potential for downstream establishment in the future. Burbot are difficult to sample, especially in large rivers, so we recommend sampling techniques to monitor the expansion of burbot in lotic and lentic habitats of the upper Colorado River Basin as well as highlight research opportunities associated with this invasion. Chapter 2 - Burbot (Lota lota L.) and white suckers (Catostomus commersonii L.) are managed as invasive species in the upper Colorado River Basin and physical barriers to their upstream dispersal could be important tools for preventing their spread. A three-tiered lab-based experimental approach was used to define design parameters for both species utilizing a hybrid barrier that combines a vertical drop with a downstream velocity segment. The first tier of the study measured fish jumping ability over a range of waterfall height × plunge pool depth treatments to refine waterfall design parameters. Jumping attempt and waterfall exploration data were collected in each trial to allow a novel approach for examining the behavior associated with individual motivation to ascend the barrier, and to confirm that all height × depth treatments were challenged. The second tier of the study used constant acceleration trials (CATs) to define the length-specific burst transition (Bt) from aerobic (high-endurance; sustained) to anaerobic (rapid-fatigue; burst) swimming. Finally, the third tier of the study used fixed velocity trials at velocities > Bt to collect anaerobic endurance data that were used to solve Peake's equation to identify velocity × barrier length combinations that prevented upstream passage. To account for peak-performing individuals, upper 99% prediction intervals were used to determine design criteria that would prevent passage of fish of the total length (TL) in their system of interest. Minimum waterfall heights > 85% and 100% of the TL of the largest white sucker and burbot, respectively, in the system were found to prevent passage. Coupling these heights with plunge pools < 40% and 30% of white sucker and burbot TL increases the difficulty these species have ascending the fall. The CATs indicated that velocity barriers that deliver minimum velocities of 4.0 and 3.2 times the TL of the largest white sucker and burbot, respectively, in the system will ensure anaerobic swimming and thus fatigue fish prior to leaping attempts. A variety of velocity barrier length × velocity design parameters are defined for each species to prevent passage based on the FVTs and Peake's equation analysis.
Open Access
Mitigation measures for barriers to Great Plains fish migration
(Colorado State University. Libraries, 2015) Ficke, Ashley D., author; Myrick, Christopher, advisor; Bestgen, Kevin, committee member; Fausch, Kurt, committee member; Thornton, Christopher, committee member
To view the abstract, please see the full text of the document.
Open Access
Pathogen vectors at the wildlife-livestock interface: molecular approaches to elucidating Culicoides (Diptera: Ceratopogonidae) biology
(Colorado State University. Libraries, 2016) Hopken, Matthew W., author; Huyvaert, Kathryn P., advisor; Piaggio, Antoinette J., advisor; Bestgen, Kevin, committee member; Kondratieff, Boris, committee member
Emerging infectious diseases (EIDs) continue to threaten human and animal welfare worldwide. Vector-borne pathogens are particularly concerning because of their ubiquity, pathogenicity, and lack of predictably due to insufficient ecological and evolutionary knowledge regarding vector species. Biting midges in the genus Culicoides (Diptera; Ceratopogonidae) have been implicated in the transmission of highly pathogenic viruses and parasites. In North America, the complete transmission cycles of many of these pathogens need further elucidation as outbreaks occur in the absence of known vector species. Further, our knowledge about the evolution and ecology of most Culicoides species is limited at best. The focus of research has been morphological identification and distribution of some North American Culicoides species, particularly those that are known pathogen vectors, but little is known about the phylogeny, ecology, behavior, and vector competence of many other species, some of which may prove to be important vectors. Ultimately, risk assessments and management of pathogens transmitted by Culicoides in North America are limited by this lack of knowledge and these limitations prove to be disastrous. Large and damaging outbreaks of Culicoides-transmitted viruses around the globe in the last two decades have raised concerns that North American livestock and wildlife are at risk. These threats, in conjunction with the lack of knowledge about vector species, led to the current research so that we can more insight into Culicoides biology and be proactive in preparing for future outbreaks. In chapter 1, I argue for more research into the biology of Culicoides in North America. In particular, I highlight our lack of information about all potential vector species, draw attention to the issues with the current taxonomic designations, discuss the main pathogens of concern transmitted by Culicoides, and then explore outbreaks of bluetongue virus in Europe as a case study illustrating how insufficient knowledge can lead to significant impacts on agriculture and the economy. I also summarize all known and potential vector species in North America to establish recognition of the tenuous nature of data used to incriminate or exclude some Culicoides species as vectors. I end with a discussion of the importance of systematics to research and management of vector-borne diseases and make a call for more Culicoides-based studies to minimize the biological, ecological, and economic damages caused by the introduction of exotic pathogens. In Chapter 2, I investigated the phylogentic relationships of the three known and described species in the C. variipennis species complex. In North America, two currently recognized vector species, C. sonorensis and C. variipennis, are thought to drive the transmission of bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV), respectively. Both species, along with a non-vector species C. occidentalis, belong to a morphologically similar species complex, the C. variipennis complex. The taxonomic history of this complex is convoluted due to the limited number of morphological characters that are species-diagnostic. My objective was to evaluate the current taxonomy of the C. variipennis species complex using multi-locus molecular phylogenetics and population genetic approaches in order to understand evolutionary relationships and historical biogeography within the complex. I determined that molecular data do not support the current taxonomy of the three species in the C. variipennis complex. In fact, phylogenetic approaches demonstrated very little resolution at the species level within the C. variipennis complex, except for a single clade that represented C. occidentalis. I detected weak population genetic structure using two nuclear loci, but this weak structure did not correlate with morphological species identification. I suggest a taxonomic reevaluation of this species complex is sorely needed so that more accurate species identification and distributions can be obtained. Improved species designations lead to more precise inferences about ecology and evolution of vector species. Through this taxonomic demystification, we can better grasp sylvatic transmission cycles and prepare for outbreaks of both domestic and foreign pathogenic viruses. In Chapter 3, I investigated host choice of Culicoides species collected in North America using DNA-based bloodmeal analyses. In North America, we currently lack the ability to understand transmission networks and assess outbreak risk for Culicoides-borne pathogens as our knowledge base of trophic ecology is meager at best. Knowing the diversity of vertebrate hosts for Culicoides can help identify susceptible species and pathogen reservoirs, and can lead to the detection of new vector species. The objective of this study was to identify the diversity of Culicoides hosts in North America. I sequenced two vertebrate mitochondrial genes (cytochrome oxidase I and cytochrome B) from blood-engorged Culicoides. I detected the mitochondrial DNA of 12 host species from five different Culicoides species and the C. variipenis species complex. The hosts included both mammals and birds. I documented new host records for some of the Culicoides species collected. The majority of the mammalian hosts were large ungulate species but I also detected a lagomorph and a carnivore. The bird species that were detected included House Finch and Emu, the latter is evidence that the species in the C. variipennis species complex are not strictly mammalophilic. These results demonstrate that Culicoides species will feed on multiple classes of vertebrates and may be more opportunistic in regards to host choice than previously thought. Throughout the dissertation, I have drawn attention to the areas for which we lack the most knowledge regarding North American Culicoides, illuminated the evolutionary relationships and taxonomic discrepancies in the C. variipennis complex, and improved our understand of Culicoides host choice. These are the first steps towards developing an improved understanding of Culicoides biology, in general, and the sylvatic cycles of Culicoides-borne pathogens, in particular. My research has also raised other important questions that deserve more attention so that we can better grasp the impacts that anthropogenic change has on Culicoides ecology, evolution, and pathogen transmission. As we increase our knowledge about this important group of insects, the ability to predict, prepare, and mitigate the economic and ecological damage from disease outbreaks will be greatly improved.
Open Access
Shifting sands: drivers and mobilization of fine sediment on the Cache la Poudre River following a wildfire
(Colorado State University. Libraries, 2024) Katz, Aaron, author; Wohl, Ellen, advisor; Bestgen, Kevin, committee member; McGrath, Dan, committee member
The Cameron Peak wildfire (840 km2) of 2020 led to widespread but varied detrimental effects throughout the Poudre River watershed (4,895 km2). The Poudre River flows through a high gradient canyon section with a somewhat unimpaired flow regime before it reaches a low gradient transition zone with several human impacts including channel modifications and flow reduction. Burned tributaries contributed elevated levels of fine sediment (< 2 mm) to the mainstem Poudre within the canyon, and in 2021 a large debris flow in Black Hollow Creek, a canyon tributary, delivered substantial amounts of material, including fine sediment, directly into the mainstem Poudre River. This led to a major fish kill and the transportation and deposition of fine sediment for at least 100 km downstream. In the transition zone, extensive fine sediment deposits either partially blocked or filled several channel margin backwaters and side channels, which are important habitats for native fish, and fine sediment filled interstices of coarse substrate grains in the mainstem river, which impacts benthic macroinvertebrate and fish spawning habitat. I quantify the degree of fine sediment retention along 100 km of the Poudre River by measuring reach-averaged fine sediment volumes and embeddedness and use model selection of multiple linear regression models to determine whether distance downstream from the sediment source or reach-scale geometric variables are the primary drivers of fine sediment retention. I also conduct a flushing flows study using 2-dimensional hydraulic modelling to determine the discharge required to mobilize the substrate at four sites along the longitudinal gradient of the study area representing different geomorphic settings and hydrologic regimes. Results from model selection using Akaike's Information Criterion corrected for small sample size (AICc) show that for both metrics of fine sediment retention, reach location (canyon vs. transition zone) is the primary driver of sediment retention, but some reach-scale variables are significant predictors of fine sediment retention. Both fine sediment retention metrics (site-averaged volumes and embeddedness) are greater in the transition zone. At the reach scale, gradient and cross-sectional area are both significant predictors of embeddedness, and models with gradient as a predictor variable have substantial support in explaining site-averaged fine sediment volumes. A mixed model of embeddedness at the transect level with bedform as the fixed effect nested with site as the random effect indicates that fine sediment is preferentially retained in pools and that all backwaters are 100% embedded. Although there are only three sites upstream of Black Hollow, fine sediment retention is either greater or not statistically different than canyon sites downstream of Black Hollow. Hydraulic modelling of the 2-, 5-, and 10-year recurrence interval flows at four sites indicates major differences in the magnitude and frequency of bed substrate mobilization between the canyon and transition zone. At a high gradient canyon site, the 2-year flow mobilizes a substantial portion of the bed, while at transition zone sites, bed mobilization occurs only at the 5- or 10-year flow level. I posit that artificially reduced flows in the transition zone are responsible for the lack of bed mobilization and will lead to longer residence times of fine sediment and prolonged impacts to aquatic ecosystems. This study adds to the literature by investigating post-fire fluvial responses at a greater spatial scale than most previous studies of the matter. By quantifying spatial distribution, physical drivers, and mobilization potential of fine sediment following a large wildfire on a major river, we can better understand how large rivers with varied human impacts respond to major disturbances and make informed management and restoration decisions going forward.