Biology Theses and Dissertations

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    Marine influence on juvenile fish trophic ecology and community dynamics in Maryland's northern coastal lagoons
    (2013) O'Brien, Michael Henry Patrick; Secor, David H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Marine influence on Maryland's juvenile lagoon fish community was examined under varied levels of internal and external forcing. In 2009, stable isotope analysis showed increasing marine carbon dependency by bay anchovy with decreasing distance to the marine inlet. Following large seagrass losses, no similar trend was detected in 2012. Weakfish showed no structured dependence on marine carbon in either year. Diet contents lacked corresponding year-to-year changes in pelagic versus benthic prey items. In 2009, serial changes with distance to the inlet occurred in species assemblage, which may have been associated with internal seagrass structure. No gradient occurred in 2012. Analysis of a 24-year survey indicated a shift from marine-pelagic to structure-oriented species, associated with increased seagrass and tide level, and decreased North Atlantic Oscillation index. In Maryland's northern lagoon, the strength of marine influence on juvenile assemblages depended on the interplay between internal bay structure and external marine forcing.
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    FISH ASSEMBLAGE STRUCTURE IN MARYLAND'S COASTAL LAGOON COMPLEX
    (2005-08-17) Murphy, Robert; Secor, David H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fish assemblage structure of Maryland's coastal lagoon complex was analyzed for spatial and seasonal patterns for the period 1991-2000. Non-metric multidimensional scaling ordinated sites from Maryland's state trawl and seine surveys into discrete groups associated with each embayment. Dominant species from both surveys included <i>Callinectes sapidus</i>, <i>Anchoa mitchilli</i>, <i>Leiostomous xanthurus</i>, <i>Bairdiella chrysoura</i>, and <i>Brevoortia tyrannus</i>. One hundred two species were identified in the surveys, with total species richness highest in Chincoteague and lowest in Assawoman and Sinepuxent. The seine survey had the lowest catch-per-site in Chincoteague Bay while the other three embayments were of similar magnitude. The trawl survey had the lowest catch-per-site in Sinepuxent Bay (3,079) and the highest in Assawoman Bay (27,146). There was clear seasonality in assemblage structure with peak abundance and diversity in the summer compared to other seasons. Factors influencing the structure of Maryland's coastal lagoon complex included proximity to oceanic exchange and trophic status.