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
5 results
Search Results
Item EFFECTS OF ENVIRONMENTAL VARIABLES AND CHANGES IN SEASONAL PATTERNS ON SPATIAL DISTRIBUTIONS OF JONAH CRABS (CANCER BOREALIS) AND ATLANTIC ROCK CRABS (CANCER IRRORATUS) IN GEORGES BANK AND THE MID-ATLANTIC BIGHT, USA(2023) Wade, Kaitlynn Jean; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The economic and commercial importance of Jonah crabs (Cancer borealis) and Atlantic rock crabs (Cancer irroratus) has increased greatly in the USA. The objectives of my research were to determine spatial distributions, habitat preferences, and potential seasonal movements of both species. Data were obtained from the offshore Northeast Fishery Science Center bottom trawl surveys. Analyses included kernel density estimates, generalized additive models, empirical cumulative distribution functions, and ANOVAs. The spatial distributions of Jonah and Atlantic rock crabs changed over time during the 1970s – 2000s. Compared to Atlantic rock crabs, Jonah crabs preferred slightly warmer temperatures, deeper depths, and muddier sediments. Seasonally, Jonah crabs were found farther offshore in the winter and closer to shore in the fall and spring. Atlantic rock crabs were found closer inshore in the winter and spring and more offshore in the fall. Both species were found to have different seasonal patterns in the Mid-Atlantic BightItem 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 Shellfisheries and Cultural Ecosystem Services: Understanding the Benefits Enabled through Work in Farmed and Wild Shellfisheries(2020) Michaelis, Adriane Kristen; Shaffer, L. Jen; Anthropology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As commercial shellfish aquaculture continues to expand in the United States (US), industry supporters promote the ability of bivalve shellfish to provide ecosystem services, suggesting aquaculture’s potential to ecologically and economically supplement wild shellfisheries (Beck et al., 2011; van der Schatte Olivier et al., 2018). Within this discussion of bivalve-related benefits, sociocultural benefits are largely absent (Alleway et al., 2018). This oversight hinders industry growth as it: 1) ignores evidence suggesting sociocultural benefits are more salient to individuals than other types of ecological benefits (Daniel et al., 2012) and 2) does not acknowledge the high level of job satisfaction associated with fisheries-based livelihoods precisely because of their many linked sociocultural benefits (Pollnac & Poggie, 2006; Smith & Clay, 2010). It is reasonable to assume that shellfish aquaculture might provide similar benefits, but this has not been considered in aquaculture’s promotion and development. To address this lapse, this dissertation detailed sociocultural benefits related to aquaculture and wild shellfisheries using an ethnographic approach framed by ecosystem services. Three complementary studies blending semi-structured interviews, photovoice interviews, participant observation, and Q methodology were conducted, targeting US shellfisheries at three scales: 1) within the state of Maryland, 2) within seven total states in the Chesapeake Bay, Gulf of Mexico, and New England regions and 3) throughout the US. Results illustrated that cultural ecosystem services are important to individuals working with shellfish and were used to create the first comprehensive list detailing the benefits enabled through work with shellfish. Project participants perceived the value of these benefits differently, and views were most strongly linked to participant role in the industry rather than other attributes. Results showed that, for the most part, shellfish aquaculture was able to provide similar benefits to a wild shellfishery. Findings from this study are relevant to both shellfisheries promotion and management as results highlight not only the range of benefits enabled through shellfisheries, but also the diversity of views and values held by industry members. Additionally, this project provided an excellent case study with which to investigate the complexity of linked and changing ecosystem services.Item Mark-Recapture Assessment of the Recreational Blue Crab (Callinectes sapidus) Harvest in Chesapeake Bay, Maryland(2016) Semmler, Robert Semmler; Reaka, Marjorie L; Hines, Anson H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In Maryland, commercial blue crab (Callinectes sapidus) harvests are monitored through mandatory, annual harvest reporting, but no monitoring exists for recreational fishers. This study used a large-scale mark-recapture program to assess relative exploitation between the recreational and commercial fishing sectors in 15 harvest reporting areas of Maryland, then incorporated movement information and extrapolated reported commercial harvest data to generate statewide estimates of recreational harvest. Results indicate spatial variation in recreational fishing, with a majority of recreational harvests coming from tributaries of the Western Shore and the Wye and Miles Rivers on the Eastern Shore. Statewide, recreational harvest has remained 8% as large as commercial harvest despite management changes in 2008, and remains a larger proportion (12.8%) of male commercial harvest. In addition, this study provides detailed spatial information on recreational harvest and the first information on rates of exchange of male crabs among harvest reporting areas.Item HISTORICAL EFFECTS OF FISHING ON AGE STRUCTURE AND STOCK MIXING IN NORTHWEST ATLANTIC BLUEFIN TUNA(2015) Siskey, Matthew Ryan; Secor, David H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bluefin tuna support important fisheries in the Northwest Atlantic Ocean, which have declined in yield from intense, size-selective exploitation. Age structure, size-at-age, and stock composition were investigated as principal responses to exploitation, utilizing otolith microstructural and chemical analysis. To evaluate otoliths as ageing structures, annulus formation was compared to temperature-associated oscillations in otolith strontium:calcium. Evaluation of otolith stable isotope measures used in stock composition analyses indicated significant differences in δ18O measurements between laboratories, but not δ13C values. Comparisons of age structure, size-at-age, and stock composition over three periods (1974-1978, 1996-2002, 2009-2014) coinciding with the cycle of exploitation intensity suggest size-selective fishing caused (1) age truncation, where median age declined (14 to 6 years); (2) minor changes in size-at-age; and (3) fluctuating stock composition, with peak mixing in the 1990s (48% eastern stock contribution). Size-specific reductions in fishing mortality could contribute to recovery through more frequent production of strong year-classes.