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Marine Ecology Progress Series

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MEPS 334:273-286 (2007)  -  doi:10.3354/meps334273

Winter energy storage dynamics and cohort structure of young-of-the-year bluefish Pomatomus saltatrix off North Carolina

James W. Morley1,*, Jeffrey A. Buckel1, Thomas E. Lankford Jr.2

1Department of Zoology, Center for Marine Sciences and Technology, North Carolina State University, 303 College Circle, Morehead City, North Carolina 28557, USA
2Department of Biological Sciences and Center for Marine Science, University of North Carolina at Wilmington, One Marvin Moss Lane, Wilmington, North Carolina 28409, USA

ABSTRACT: The ecology of overwintering young-of-the-year bluefish Pomatomus saltatrix off North Carolina, USA, was examined for the 2001 and 2002 year-classes, to test the hypothesis that overwinter mortality affects the recruitment of summer-spawned bluefish. A trawling survey was conducted in Onslow Bay, North Carolina, from October 2001 to May 2002 and from September 2002 to June 2003 to determine bluefish abundance, cohort structure, energy density of white muscle and liver, and gut fullness. Up to 4 transects ranging from 0.4 to 16.1 km from shore were sampled monthly. Abundance of bluefish in Onslow Bay was high during the fall and declined with decreasing temperature in both years. Winter abundance was related to winter severity, with higher catches during the more mild winter of 2001 to 2002. At least 3 young-of-the-year cohorts were observed in both years. Gut fullness values generally followed temperature patterns, with reduced feeding during the winter. Energy reserves in white muscle and liver tissues peaked in November with larger fish having disproportionately more energy. However, by mid-winter there was little difference in energy reserves between the cohorts. These data suggest that larger fish deplete a greater portion of their energy stores as the season progresses while smaller fish deplete energy more slowly. Catch data show that summer-spawned bluefish survive the winter, but the magnitude of overwinter mortality remains uncertain.

KEY WORDS: Bluefish · Pomatomus saltatrix · North Carolina · Allometry · Lipids · Overwintering · Energy reserves · Mortality

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