Date of Award

Winter 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Committee Director

Cynthia M. Jones

Committee Member

Fred C. Dobbs

Committee Member

Alexander Bochdansky

Committee Member

Christian Reiss

Abstract

I describe a new preparation technique that increases readability of otoliths, along with criteria for the interpretation of otolith microstructure of bluefish, Pomatomus saltatrix, collected from Florida to New York during 2001-2003 (n = 2652). I validated annulus formation in otoliths for ages 1 to 8 using marginal increment analysis and thus extended validation by four years to include the preponderance of age classes in the catch. Although otoliths are typically superior for ageing, bluefish are routinely aged with scales; thus a side-by-side comparison of otoliths versus scales is necessary before otoliths can supplant scales. When compared, precision was highest with sectioned otoliths, exceeding 87% across all years, and exceeding 99% within 1 year up to ages 13. In contrast, scales tended to over age age-1 through age-5, and under aged age-7 and older in comparison with sectioned otoliths. Having demonstrated the value ofotoliths, I used ages estimated from them to evaluate age distribution of various gears used in the fishery and calculated growth parameters and batch fecundity. When I evaluated my coast wide collections, I noted that gears caught different age ranges yet there were no significant differences in the von Bertalanffy growth parameters compared by sex, year, and between the South Atlantic and Middle Atlantic Bights using likelihood-ratio tests. The estimated Atlantic von Bertalanffy model growth parameters were Linf = 815.3mm ± 15.3, k = 0.311 ± 0.03, t0 = -.301 ± 0.18. Histology, trends in gonadosomatic index, and oocyte diameter frequencies were used to determine bluefish spawning locations and patterns. Bluefish are multiple spawners with indeterminate fecundity. The presence of all stages of development in fully mature ovaries indicates that bluefish have asynchronous oocyte development. Mean age at first maturity for bluefish provided evidence for larger sizes than previously estimated with females maturing at 1.90 years and 480 mm. Histological samples showed imminent spawning in Florida and North Carolina during March to April, and from April to August in Virginia to New York, supporting the hypothesis of continuous spawning from South Atlantic Bight to Middle Atlantic Bight. My estimates of fecundity at size are lower than previously published results.

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DOI

10.25777/vagc-x096

ISBN

9781109793413

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