Browsing by Subject "Invasive"
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Item Control of the common carp through species-specific toxin delivery systems and biocontrol by bluegill sunfish(2018-03) Poole, JoshuaThe Common carp (Cyprinus carpio, or ‘carp’) is an invasive fish native to Eastern Europe and Asia and is one of the world’s most ecologically harmful species. It is known to cause issues with water clarity, increase nutrient levels, reduce aquatic vegetation, and impact waterfowl. There are many existing strategies to control carp, however, each have various issues. This has led to the search for more practical, sustainable, or broadly applicable control strategies. I investigated two emerging control strategies for carp: biocontrol of carp by bluegill sunfish, and selective toxin delivery systems. Biocontrol has been used successfully for decades in the agriculture industry; however, biocontrol for aquatic pest control is still rudimentary. Previous evidence has suggested that bluegill sunfish (Lepomis macrochirus) may be capable of controlling carp recruitment by consuming eggs and larvae of carp, however, this has never been tested in natural, whole-lakes. To test if bluegill were capable of limiting carp recruitment in natural lakes, I conducted a two-year experiment where carp were stocked into natural lakes, and bluegill were stocked in half of the lakes. The recruitment success of carp was assessed at various stages in first growing season of development: (1) the egg stage, (2) the post-larval juvenile stage, and (3) the end-of-season juvenile stage. The results indicate that bluegill predation had a major effect on the egg stage and the abundance of post-larval carp, but the abundance of end-of-season carp were affected by other processes (such as density-dependence). This is the first experiment to my knowledge that has conducted an experiment on biocontrol of a fish using multiple whole-lake manipulations. This may provide the most robust evidence to date that bicontrol of a fish is possible in natural systems. Next, I performed an analysis to examine lake characteristics that cause bluegill abundance to be low, and thus define conditions where bluegill density is too low to control carp through biocontrol. My model incorporated 12 lake and watershed variables that were used to explain variation in bluegill sunfish catch-per-unit-effort (CPUE). Of those variables, depth and water clarity had the largest effect. Specifically, bluegill abundance declined rapidly in lakes with maximum depths of less than 7 m, and a secchi disk depth less than 0.7 m. These conditions are indicative of lakes that winterkill, thus aeration may be a feasible way to stabilize bluegill populations in these systems. Last, I incorporated antimycin-a (ANT-A), a known fish toxicant, into a corn-based bait and conducted a series of experiments to determine its toxicity, leaching rate, and species-specificity. My results showed that ANT-A was lethal to carp at doses ≥ 4 mg/kg and that the amount of ANT-A that leached out of the bait in 72 h was not lethal to carp or bluegill (Lepomis macrochirus). Species-specificity trials were conducted in 227 L tanks, in which carp were stocked with three native species representing families that occur sympatrically with carp in my study region: the fathead minnow (Pimephales promelas), yellow perch (Perca flavescens) and bluegill. These trials showed high mortality of carp (46%) and fathead minnows (76%) but no significant mortality of perch or bluegill. Finally, a pond study, which used the same species composition except for fathead minnows, resulted in 37% morality among adult carp and no mortality among perch or bluegill. My results suggest that corn-based bait that contains ANT-A could be used to selectively control carp in ecosystems dominated by percids or centrarchids, such as lakes across the Great Plains ecoregion of North America, where carp are especially problematic.Item Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review(2007) Knight, Kathleen S; Kurylo, Jessica S; Endress, Anton G; Stewart, J. Ryan; Reich, Peter BIn this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.Item An examination of the impacts of invasive woody vegetation on grassland birds and waterfowl(2013-12) Thompson, Sarah JeanEfforts to remove woody vegetation are becoming a management priority in many grassland regions. Encroaching trees are thought to degrade habitat for grassland birds by altering predator communities, increasing competition, altering food webs, or by disrupting habitat selection patterns based on historical landscapes. Once established, trees and shrubs can be difficult and expensive to eradicate from grasslands. In order to best utilize limited conservation resources, grassland managers require information on how detrimental trees are for target species and where tree-removal actions might be the most beneficial. My dissertation research focused on exploring the consequences of woody vegetation encroachment on grassland bird habitat selection and waterfowl nest survival in western Minnesota. I also examine the results of experimental tree-removal on grassland songbird abundance. Most species of grassland birds exhibited strong patterns of tree avoidance. Tree-avoidance may be a more important driver of habitat selection than grass extent or quality in this landscape. Contrary to expectations, waterfowl nest survival was not related to the amount or proximity of woody vegetation. The effects of experimental tree-removal on songbirds were mixed. Grassland birds responded negatively for several years following initial treatment, but eventually the removal led to increases in abundance compared to control sites. The initial negative response was likely due to disturbance on the site, including fire treatments intended to reduce tree re-growth.Item Perceptions of Invasive Species and Their Control Among the MN Tourism Industry(University of Minnesota Tourism Center, 2014) Schneider, Ingrid E.; Qian, XinyiThis project sought baseline information on perceptions of invasive species and theie control among the Minnesota tourism industry. The majority of respondents agreed that both invasive plant & aquatic invasives were harmful to Minnesota’s environment, economy & society. Similarly, the majority of respondents indicated all 7 control methods presented in the questionnaire would be effective to control invasive species.Item Source-sink population structure of invasive common carp in a model Midwestern watershed: empirical evidence and notes on management(2014-08) Koch, Justine DanielleEffective management of invasive fishes requires a detailed understanding of the factors that influence population structure and persistence across relevant spatial and temporal scales. It has been hypothesized that the common carp (Cyprinus carpio) is often invasive in the North American Midwest due to its propensity to utilize shallow, predator-free basins as productive nursery habitat. Although it has been demonstrated that such basins often support extremely high abundances of young carp, the fate of these carp is unknown. To determine whether these putative nurseries serve as important sources of recruits at a watershed scale, we used mark-recapture and genetic assignment methods to investigate carp recruitment in a system of interconnected lakes, ponds, and associated wetlands in central Minnesota. Annual trap net surveys in 4 lakes and 8 ponds in the Phalen Chain watershed from 2009-2013 revealed that young-of-year carp were found exclusively in shallow pond habitats. Mark-recapture studies in 2011 and 2012 indicated that, of the 613 carp marked in one of the putative nursery ponds, ~31% of recaptured carp (25 of 80) had emigrated from the nursery pond to a connected water body. Microsatellite analysis of carp tissue samples (n=1041) from all basins throughout the watershed and from individuals moving between lakes and putative nurseries during the spawning season revealed two genetically distinct strains of carp within the watershed. The distribution and movements of genetically distinct carp revealed patterns in dispersal and colonization consistent with the carp nursery hypothesis (i.e. source-sink population structure). Additionally, there was evidence of reproductive homing by adult common carp. Our results and continued research on carp recruitment dynamics will aid in the development of population models and integrated pest management strategies to combat this highly invasive species.Item A Survey of Winter-Hardy Prunus Species: Evaluation of Seed Germination, Seedling Establishment, and Pollen Viability(2016-05) Kostick, SarahPrunus is a genus that contains a number of economically important fruit crops (e.g. apricots, sweet and tart cherries, and plums) as well as many ornamental species. However, some Prunus species (e.g. P. serotina Ehrh) have escaped cultivation and become invasive. By evaluating seed germination, seedling establishment, and male fertility, this thesis characterized the invasive potential of winter-hardy Prunus cultivars. The winter-hardy cultivars examined, were characterized by high male fertility and variable seed germination and seedling establishment. Due to relatively low germination percentages and/or poor seedling establishment, the majority of cultivars examined will probably not become invasive. However, this thesis identified a few cultivars that could potentially become invasive. Future work should focus on the invasive potential of the cultivars P. americana Marsh ‘Hazel’, P. monsoniana Wight and Hedrick ‘Whittaker’, Prunus spp. ‘Hennepin’ and ‘South Dakota’, and all tart cherry (P. cerasus L.) cultivars examined.