Browsing by Author "Morley, James Walter"

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    Ecology of Juvenile Bluefish (Pomatomus saltatrix) overwintering off North Carolina
    (2004-07-30) Morley, James Walter; Jeffrey A. Buckel, Committee Chair
    Ecology of overwintering young-of-the-year bluefish (Pomatomus saltatrix) off North Carolina was examined for the 2001 and 2002 year-classes. This study addressed the hypothesis that overwinter mortality affects the recruitment of summer-spawned bluefish. A trawling survey was conducted in Onslow Bay, NC from October 2001 to May 2002 and from September 2002 to June 2003. Up to four transects were sampled monthly each ranging from 0.4 to 16.1 kilometers from shore. Lipid content of white muscle and livers were determined using soxhlet extraction. Abundance of bluefish in Onslow Bay depended on winter severity, as catches during the winter were higher during the more mild winter of 2001-02. The highest catches of bluefish occurred within two miles of shore and were strongly associated with anchovy and clupeid prey. Bluefish recruitment was shown to be more complex than previously supposed; at least three young-of-the-year cohorts were observed for both year-classes. Energy reserves peaked in November with larger fish having disproportionately more energy. However, by mid-winter there was little difference in energy storage between the cohorts. These data suggest that larger fish deplete a greater portion of their energy stores as the season progresses while smaller fish defend their energy levels by feeding. Catch data show that summer-spawned bluefish survive the winter despite having lower energy reserves. However, the magnitude of overwinter mortality remains uncertain.