UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
4 results
Search Results
Item INTEGRATING BIOTELEMETRY AND HYDROACOUSTIC DATA TO ESTIMATE THE ABUNDANCE OF THE FALL SPAWNING RUN OF ATLANTIC STURGEON IN THE MARSHYHOPE CREEK-NANTICOKE RIVER SYSTEM(2022) Coleman, Nicholas; Secor, Dr. David H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Once thought to be extirpated, fall spawning runs of Atlantic sturgeon (Acipenser oxyrinchus) have been rediscovered in the Nanticoke River-Marshyhope Creek system in Maryland and are currently listed as an endangered species within the Chesapeake Distinct Population Segment. Previously tagged adults predominate survey captures, suggesting a very small population size. A key challenge is to estimate abundance for such a small population distributed between presumed spawning reaches of the connected Nanticoke River and Marshyhope Creek. This study leverages data collected from a dense telemetry receiver array and multiple side-scan sonar surveys conducted from August to October to estimate reach specific and superpopulation abundances in 2020 and 2021. I modified an approach that integrates mobile hydroacoustic data with biotelemetry, here applying for stationary telemetry receiver data. In 2020 and 2021, I estimated that 36 (95% confidence interval: 25-55) and 74 (95% confidence interval: 52-109) sturgeon used the Nanticoke River-Marshyhope Creek system, respectively. The higher estimate in 2021 coincided with higher sonar count data and low and stable river flows and temperature. Still, this large difference has no clear cause. Overall, run estimates support previous hypotheses that the Nanticoke system supports a very small population and that both the Marshyhope Creek and upper Nanticoke River serve as important areas for spawning activity. Going forward, enhanced sampling of the Upper Nanticoke River and targeted analysis assessing the relationship between phenology and environmental conditions would further develop our understanding of interannual changes in spawning run abundance.Item Essays on Regulatory Uncertainty & Energy Development in the American West(2021) Hunt, Jeffrey; Linn, Joshua; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation undertakes an analysis of regulation in the American West, investigating the effects of expropriation uncertainty and technological change in the leasing process.The first chapter explores the possible expropriation of drilling rights due to the addition of the sage-grouse under the Endangered Species Act. Leveraging prior decisions of the US Fish and Wildlife Service, I estimate there was a 52.6% chance the sage-grouse would be listed. Using the real-options framework of Kellogg (2014) and constructing an extension of his simulation to accommodate expropriation risk parameterized by real-world drilling data, I find that developers are expected to delay spudding wells to wait out the uncertainty. This result is corroborated with a Cox proportional hazards model. Additionally, using a difference-in-differences model I find robust evidence that developers reduce their bids for leases commensurate with the expected reduction in profits from possible regulation, and using a conditional logit discrete choice model I find evidence that firms abandon core sage-grouse habitat. Lastly, I find no evidence that developers increase the extraction rate of drilled wells. The second chapter investigates expropriation risk in the context of ozone pollution controls from the Environmental Protection Agency. Here, I find a hurry-up-and-drill response. I place this result within the literature of the green paradox, and find that the EPA regulation did not produce a green paradox but if costs were lower, or if the regulation were modified, a green paradox would have existed and briefly result in higher emissions under a stricter regulatory regime. The policy takeaway is that regulators should avoid a long announcement period, as it gives developers time to drain wells before regulation occurs. The third chapter is a cost/benefit test of auctioning drilling leases online rather than in-person. I leverage the fact that only specific leasing jurisdictions transitioned to an online system called EnergyNet in late 2016 to estimate the causal effect of moving to online leasing. I estimate that a given parcel sold online versus in-person will generate 40% higher bids against only a 2% extra cost.Item Identifying the elusive dwarf wedgemussel habitat through modeling and field approaches(2014) Campbell, Cara Ann; Prestegaard, Karen L.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Habitat identification is an important step in the conservation of at-risk species, but difficult due to the small, fragmented populations of rare species. In particular, fine-scale habitat features that constrain species occurrence may not be captured by landscape models. Thus, I used both modeling and field-based approaches to identify habitat characteristics for the endangered dwarf wedgemussel, Alasmidonta heterodon. Community analyses and modeling were combined to identify characteristics of suitable habitat for A. heterodon in the Maryland Coastal Plain. Community analyses suggested that landscape, rather than biological, surrogates would be preferable for predictive habitat modeling. Subsequent MaxEnt modeling associated A. heterodon habitat in the Maryland Coastal Plain with the following variables: depth to the water table, pasture/hay land cover, woody wetlands, low intensity development, Tertiary-aged sediments, and minimum elevation. The results from this model directed field work to evaluate thermal, geochemical, and physical characteristics of A. heterodon reaches throughout the species' range. Paired air-water temperature sensors placed in A. heterodon reaches suggested a potential thermal threshold of 29°C. Southern sites had higher maximum water temperatures but exhibited less diurnal variation and lower rates of temperature change than northern sites; characteristics that suggest intermediate to deep groundwater sources. Physical and chemical characteristics were measured along the length of Flat Brook, a stream with A. heterodon in the Delaware River basin. Data indicated that the mussel occurred in reaches that were stable during bankfull and lower discharges and water chemistry data indicated saturation with respect to aragonite during summer base flow. Field studies suggest several potential essential habitats for A. heterodon: (1) habitats with stable streambeds at bankfull and lower discharges; (2) stream waters in equilibrium with aragonite precipitation during baseflow conditions; and (3) habitats with maximum temperatures < 29°C and stable thermal regimes. The different thermal regimes and contributing groundwater sources between northern and southern populations suggest that geographic region be a consideration in species' reintroductions. Until essential habitats are identified and management plans instituted, all populations should be similarly protected and the loss of individual populations prevented.Item Age, growth and recruitment of Hudson River shortnose sturgeon (Acipenser brevirostrum)(2005-08-10) Woodland, Ryan Jordan; Secor, David H.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Shortnose sturgeon (Acipenser brevirostrum), an Endangered Species, has experienced a several-fold increase in abundance in the Hudson River in recent decades. Age structure and growth were investigated to evaluate the hypothesis that improvements in water quality during the late 1970s stimulated population recovery. Specimens were captured using gill nets bi-monthly 2003 to 2004. Annuli in fin spine sections were determined to form at an annual rate and yielded age estimates of 5-30 years for sizes 49-105cm Total Length (n=554). Hindcast year-class strengths, corrected for gill net mesh selectivity and cumulative mortality indicated high recruitments (28,000-43,000 yearlings) during 1986-1992, which were preceded and succeeded by c. 5 year-periods of lower recruitment (5,000-15,000 yearlings). Results indicated that Hudson River shortnose sturgeon abundance increased due to the formation of several strong year-classes occurring about five years subsequent to improved water quality in important nursery and forage habitats in the upper Hudson River estuary.