Theses and Dissertations from UMD

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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 give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Now showing 1 - 4 of 4
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    The importance of female phenotype in determining reproductive potential and recruitment in Atlantic coast striped bass (Morone saxatilis)
    (2012) Peer, Adam Christopher; Miller, Thomas J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The influence of female phenotype on the reproductive potential of Atlantic coast striped bass is addressed in three key areas of research. The importance of the environment in shaping maternal phenotype was evaluated using a spawning stock time-series to evaluate possible environmental drivers of female migration timing in the Chesapeake Bay. Results showed that local and recent water temperature was the primary factor influencing timing of movement onto spawning grounds, with higher temperatures resulting in early movements. Next, two approaches were used to evaluate the influence of female energetic condition on reproductive potential. First, a field approach was used to test the hypothesis that relative total female condition (hereafter condition) has a positive influence on pre-fertilized indicators of reproductive potential (i.e., probability of spawning, relative fecundity, and relative oocyte volume). Results indicated that condition had a positive influence on residual fecundity, residual oocyte volume and indirectly on the probability of spawning. In the second approach, a laboratory experiment was conducted to test the hypothesis that female condition has a positive effect on offspring size, growth and survival. The null hypothesis that the maternal influences on offspring phenotype did not differ in the Chesapeake Bay and Roanoke River populations also was tested. In contrast to the effects of female condition on pre-fertilized indicators of reproductive potential, condition had no influence on offspring phenotype in either population. Instead, post-spawn gutted weight alone had the greatest influence on offspring phenotype, although to a lesser and potentially insignificant degree in the Roanoke River. Finally, a preliminary field evaluation was conducted in the Patuxent River, MD to determine whether maternal influences can lead to disproportionate numbers of mothers contributing to juvenile recruitment. Specifically, this study evaluated whether the variance in the distribution of half-sibling families was greater than expected by random reproductive success (i.e., Poisson process). If true, it was expected that the effective population size would be orders of magnitude smaller than the census size. Results provide preliminary evidence for higher than expected variance in reproductive success; however, methodological improvements will be necessary to confirm these results in the future
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    PATTERNS IN DISTRIBUTION, GROWTH, AND TROPHODYNAMICS OF STRIPED BASS EARLY LIFE STAGES IN THE ESTUARINE TRANSITION REGION OF UPPER CHESAPEAKE BAY
    (2011) Shideler, Allison Rae Chandler; Houde, Edward D.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Variable production of young striped bass Morone saxatilis in the estuarine transition region depends on environmental and hydrographic conditions in the estuarine turbidity maximum (ETM) and salt front region of Chesapeake Bay. Spatio-temporal variability in occurrence, growth, and diet of early life stages of striped bass and zooplankton prey were compared in years of average (2007) and poor (2008) production of striped bass juveniles. Stable isotope analyses tracked sources of carbon and nitrogen in larval striped bass diets. The estuarine copepod Eurytemora affinis was the most important prey. It and the freshwater cladoceran Bosmina longirostris dominated diets of striped bass larvae. Bosmina was relatively important in 2007. Larvae grew faster in 2007 than in 2008 and growth was fastest within and up-estuary of the ETM and salt front. Stable isotope analysis indicated that carbon from both marine and terrestrial sources supports production of striped bass larvae.
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    Assessment of local abundance, demographics, health and exploitation of Chesapeake Bay American eel
    (2009) Fenske, Kari Hammarsten; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Chesapeake Bay supports the largest U.S. harvest of American eel Anguilla rostrata, yet little is known about the underlying production rates sustaining harvests. Demographic attributes were compared between six sub-estuaries and with an unexploited population in the Hudson River. A mark-recapture experiment in the Potomac River yielded growth, abundance, and production estimates. Sub-estuaries characterized by lower salinity had a lower proportion of females, and American eels were older, slower growing and showed increased parasitism. Female American eels were larger, older, and had higher growth rates than other gender types. Local abundances were 10-fold higher in the Potomac River estuary in comparison to the Hudson River, but growth rates were similar. Mortality rates were twice as high as those in the Hudson River estuary. The production model indicated American eel recruitment and biomass decreased substantially during the past 20 years.
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    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.