Biology Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2749

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    DEVELOPING SPATIALLY-EXPLICIT ASSESSMENT TOOLS FOR EASTERN OYSTER IN CHESAPEAKE BAY
    (2011) Livings, Maude Elizabeth; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Decreasing abundance of the eastern oyster Crassostrea virginica in Chesapeake Bay is of concern because of its ecological, economic, and cultural importance. The objective of my study was to develop methods for conducting stock assessments of eastern oysters in Maryland waters of Chesapeake Bay that estimate abundance, recruitment, and fishing mortality at regional scales. First, I evaluated how spatial patterns in autocorrelation of recruitment and adult relativity density varied over time by fitting semivariogram models to survey data for each year. This information was then used to determine appropriate scales for my second objective which was to develop a stage-based model for the lower Potomac River using data from the Maryland Department of Natural Resources fall dredge survey and fishery data from the Potomac River Fisheries Commission. Estimated abundance declined to approximately 39% of that in 1990. The analyses will provide a platform for regional management of eastern oysters.
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    An evaluation of the synchronization in the dynamics of blue crab (Callinectes sapidus) populations in the western Atlantic
    (2011) Colton, Amanda Rae; Miller, Thomas J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Blue crab populations along the east coast of the United States are known to fluctuate in size annually. Previously, the degree of coherence in abundance between these populations was unknown. My research used a combination of fishery-dependent and fishery-independent data to quantify the amount of synchrony among blue crab populations and to determine the mechanisms that drive abundance fluctuations. This was done by first fitting catch-survey models to time series of survey abundance and catch to obtain absolute abundance estimates. Subsequently, I used multivariate techniques to quantify the extent and pattern of synchronization. I found that a latitudinal pattern among blue crab populations exists among all the regions except Chesapeake Bay, which appeared to be anomalous. A combination of larval mixing in the coastal ocean and a Moran effect appear to be drivers of the synchrony among blue crab populations although more investigation into these mechanisms is needed.