Theses and Dissertations from UMD
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Item 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 futureItem ALTERNATIVE MIGRATORY PATHWAYS OF JUVENILE STRIPED BASS IN THE PATUXENT RIVER ESTUARY, MARYLAND(2012) Conroy, Christian William; Secor, David H.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although highly migratory striped bass Morone saxatilis utilize spatially diverse and dynamic estuarine systems as nurseries, early dispersal behaviors have remained largely unknown. Using otolith chemistry, we identified consistent migratory and residence behaviors in juvenile striped bass year classes. Migrants were further separated by size and age into contingents that shared similar ontogenetic dispersal thresholds. We identified a small group of larval dispersers that moved to mesohaline waters prior to reaching 6 mm. Resident juveniles experienced better early growth that migrants. Small migrants had the lowest growth rates prior to dispersal, but afterward showed enhanced growth rate. Positive growth inflections were also observed for a group of migrants that reinvaded freshwater at larger sizes. Striped bass migration seems to be controlled by individual growth trajectories, where movement is driven by poor growth in the natal habitat.Item 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.Item Growth and Physiology of Eastern and Suminoe Oysters and the Implications of Increased Habitat Complexity for Associated Oyster Reef Fauna(2011) Kelly, Christopher James; Newell, Roger I.E.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The introduction of a non-native oyster species (Crassostrea ariakensis) into Chesapeake Bay has been proposed as a way to help restore the oyster fishery and enhance the ecological services historically provided by eastern (Crassostrea virginica) oysters. A comparison of growth, mortality, and physiology between diploid C. ariakensis (Oregon strain) and diploid C. virginica was undertaken in quarantined mesocosms simulating mesohaline Chesapeake Bay. Growth of C. ariakensis was greatest during the late winter and early spring periods, with oyster condition substantially reduced during the summer due to low clearance rates and elevated respiration rates. Stunted growth and high mortality characterized the C. virginica treatment, although the reasons for this are unknown. Additional quarantined laboratory studies, conducted in Florida for both oyster species in conditions simulating a subtropical estuary examined the potential of C. ariakensis to expand southwards. While growth of C. ariakensis was comparable to that of C. virginica, mortality of C. ariakensis reached 100% by the end of the study, but remained relatively low for C. virginica. Physiological studies under quarantined temperate euhaline conditions (Wachapreague, Virginia) confirmed that C. ariakensis is physiologically intolerant to warmer water (> 20ºC) because of low clearance rates. Oysters create reefs that provide refuge for prey species, and enhanced foraging opportunities for predatory fish species. Predator-prey interactions between organisms found on oyster reefs, such as grass shrimp (Palaemontes pugio), white perch (Morone americana), and striped bass (Morone saxatilis) were conducted on habitats of varying complexity. Habitats consisted of flat sand, and medium and high complexity structures constructed in mesocosms from PVC pipe. As structural complexity increased so did the attraction of grass shrimp and white perch to structure regardless of the provision of food resources or presence of striped bass. The attraction of grass shrimp to structure decreased when high densities of conspecifics were present. The presence of prey and/or predators enhanced white perch utilization of structure and increased complexity decreased their swimming and shoaling activity. Habitat complexity and the threat of predation interact to alter grass shrimp and white perch behavior under intermediate levels of structural complexity.Item The influence of episodic river flow events on striped bass (Morone saxatilis) spawning in Chesapeake Bay, USA(2010) Jahn, Ginger Lee; North, Elizabeth W.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The upper Chesapeake Bay is an important and dynamic nursery habitat for striped bass (Morone saxatilis) eggs and larvae. The hypothesis that pulses in flow cause temperature changes that cue striped bass spawning was evaluated with field surveys and historical data analyses. Water temperatures in April and May were negatively correlated with river flow (1956-2002), suggesting that water temperatures decrease during flow events and then increase as flow diminishes, potentially providing a cue for spawning. Survey data from the upper bay in 2007 and 2008 were analyzed in conjunction with historical data on striped bass eggs in tributaries of Chesapeake Bay. Results suggest that increasing water temperatures are the dominant cue for striped bass spawning. Temperature increases after pulsed flow events may cue striped bass spawning and may result in more favorable prey abundances and better larval survival compared to years when spawning is cued by water temperature increases alone.Item ENVIRONMENTAL CONTROLS AND BIOLOGICAL CONSTRAINTS ON RECRUITMENT OF STRIPED BASS MORONE SAXATILIS IN CHESAPEAKE BAY(2008-11-30) Martino, Edward Joseph; Houde, Edward D; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The causes of >30-fold recruitment variability in striped bass Morone saxatilis were investigated in Chesapeake Bay. Factors that affect survival and growth of early-life stages were evaluated through 1) field surveys in 2001-2003 to document spatial and temporal variability in larval and juvenile abundances, 2) synthetic data analyses to provide a longer-term perspective and 3) trophodynamic and growth analyses to document how environmental variability controls and regulates variability in year-class strength. Daily discharge from the Susquehanna River in spring months controlled the distribution and apparent survival of striped bass and other anadromous fish larvae. Control of recruitment in upper Chesapeake Bay includes both direct and indirect effects of hydrological variability on egg and larval survival. In dry years (1999 and 2002), direct effects of biophysical controls resulted in low abundances of striped bass feeding-stage larvae, a consequence of reduced retention of eggs and yolk-sac larvae at the salt front and Estuarine Turbidity Maximum (ETM). The strongest year classes are produced in wet years that have high retention of eggs and yolk-sac larvae (i.e. direct effects), and a spatial and temporal match between feeding larvae and zooplankton prey (i.e. indirect effects). In moderate and high freshwater flow years (1996, 1998, 2001, 2003), indirect trophodynamic effects were most important. Striped bass larvae were strongly associated with the ETM in wet years when zooplankton prey levels also were highest in the ETM. A higher percentage of feeding larvae was observed in a wet year (2003) than in a dryer year (2001) (93% versus 35%) and faster larval growth (58% higher) occurred in the wet year. Inter-annual variability in growth and its effect on larval stage duration and cumulative mortality were sufficient to generate variability of the magnitude observed in juvenile recruitment. A forecasting model developed for age-0 striped bass recruitment that included spring flow and spring temperatures as independent variables has strong predictive capability. Growth of age-0 juveniles was density dependent, leading to diminished juvenile survival in years of high abundance through size-selective overwinter mortality. Through this mechanism, age-0 abundance levels that vary >10-fold are reduced to 3-4-fold variability at age-3. Density dependence regulates dynamics of age-0 juveniles, compensating for coarser controls over recruitment generated by environmental factors during the egg and larval stages.Item The Interrelationships Between Dissolved Oxygen and Recreational Morone saxatilis (striped bass) Catch in the Chesapeake Bay(2008-08-06) Mason, Andrew L; Lipton, Douglas W.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Declining dissolved oxygen (DO) conditions in the Chesapeake Bay negatively affect human uses of the Bay, including recreational striped bass fishing. These changes impact where, when, and if fishermen will catch a fish. Development of human-use indicator models allow for more precise quantification of low DO's effect on catch. In this study, improved modeling determined optimum DO for striped bass recreational catch in the Chesapeake to be in the range of 8-9 mg/L. Positive relationships between increased DO and catch were seen in the majority of statistical analysis for the Chesapeake. When DO is increased from 2 to 5 mg/L DO over the whole Chesapeake Bay, there is a corresponding increase in striped bass catch of 149.4%. Results from this study and others demonstrate that not only do human activities impact the form and function of ecosystems, but the use and enjoyment of those ecosystems by humans is also impaired.Item Mycobacteriosis in Chesapeake Bay striped bass Morone saxatilis(2008-04-22) Stine, Cynthia Bee; Kane, Andrew S.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Striped bass, Morone saxatilis, is an economically and ecologically important species in the Chesapeake Bay and along the East coast of the United States. In 1997 an epizootic of mycobacterial infections was discovered in the Chesapeake Bay stock and subsequent reports indicated that up to three-fourths of subpopulations of striped bass in the Bay were infected, primarily older fish. This study investigated regional and age class differences in mycobacterial infections among younger striped bass in the Chesapeake Bay, and identified putative risk factors for infection. Approximately 2,000 0+ to 3+ age striped bass, a limited number of spawning stock, and bycatch species were evaluated for microbiology, histopathology and parasitology. Mycobacterial isolates were grouped according to gas chromatography fatty-acid methyl-ester profiles and multi-locus sequencing. Twenty-nine groups of mycobacteria were discerned including M. scrofulaceum, M. septicum, M. interjectum, M. triplex/M. montefiorense, M. szulgai, M. moriokaense, M. duvalii, M. avium, M. terrae, M. pseudoshottsii/M. marinum and M. shottsii, and several putative new species. The majority of mycobacteria groups observed had host overlap. Data revealed that prevalence of mycobacterial infection increased with age, up to 59%. Location of capture was associated with higher infection prevalence in fish sampled from the Pocomoke River compared with fish sampled from the Upper Bay (1+), the Choptank River (1+) and the Potomac River (0+, 1+). The presence of copepods, isopods, acanthacephalans, nematodes and trichodinid ciliates was associated with an increased prevalence odds ratio (POR) for mycobacterial infection, while the presence of bacteria other than mycobacteria was associated with a decreased POR for 0+ fish. Gender was not a risk factor for mycobacterial infection, however, gonads from some mature fish were infected. In addition, mycobacterial infections were observed in 12 other Chesapeake Bay fishes, including Atlantic menhaden, Brevoortia tyrannus, an important prey species. Mycobacterial infections in Chesapeake Bay fish appear to be more complex than the one pathogen-one host scenario. Further, vertical and food-borne transmission cannot be ruled out. Future research requires an holistic approach including evaluation of multiple host species in association with water quality and other environmental parameters.Item MOLECULAR AND FUNCTIONAL CHARACTERIZATION OF A 15 KDA GALECTIN FROM STRIPED BASS (MORONE SAXATILIS)(2004-11-29) Henrikson, Davin Eric; Vasta, Gerardo R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)I have employed biochemical and molecular techniques to investigate the role of galectin during bacterial challenge in teleost fish, using striped bass as an experimental model. Striped bass (Morone saxatilis) possesses a 15 kiloDalton Beta-galactoside binding protein, here after called MS15. It is a single polypeptide with an experimental mass of 15,000 Daltons. In vivo, MS15 exists as a non-covalently linked dimer, with two identical carbohydrate binding sites per protein. The organization of the gene coding for MS15 was the same as other vertebrate proto type galectins, with four exons the same size between organisms and three introns varying greatly in length. These investigations have shown that galectin is localized to the dermis and lamina propia (loose connective tissue) throughout the body, to smooth vascular muscle (veins, arteries), to large circulatory cells (heterophils, monocytes), to peripheral leukocytes (tissue resident macrophages, heterophils), to rodlet cells (possible immune cell in alimentary canal), and to leukocytes throughout the gills but not to mucus-producing cells. This is similar to what is found in mammals, but differs greatly from what has been observed in other teleosts. This finding led to the hypothesis that proto type galectin in striped bass was involved in innate immunity. To test this hypothesis, galectin was characterized based on stability, carbohydrate binding specificity, and native structure. Interactions between galectin and mucus, and galectin and bacteria were then tested. Results revealed galectin binds skin mucus and agglutinates selected bacteria. Striped bass were challenged with bacteria by intradermal and intramuscular injections. Results suggest an increase in the number of galectin-positive leukocytes observed in injection sites, independent of the presence of bacteria. Also, a novel observation was the strong galectin-positive nature of rodlet cells in the esophagus, stomach, and pyloric caeca of the striped bass. The function of rodlet cells is disputed, but in striped bass, galectin was detected most strongly in rodlet cells and both circulatory and peripheral leukocytes. Collectively, these data provide the foundation for three models to explain the biochemical events involved in bacterial clearance and/or wound healing in teleost fish, with potential relevance to innate immunity in other organisms.