Date of Award

Spring 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Committee Director

Cynthia M. Jones

Committee Member

Alexander Bochdansky

Committee Member

Dayanand N. Naik

Abstract

Sheepshead recently have seen an increase in fishing pressure in Virginian waters of the Chesapeake Bay. This increase in fishing pressure has led to demands to install effective management measures to protect the fishery. However, no study regarding the population dynamics, and thus potential yield, of sheepshead has been conducted north of Cape Hatteras. We addressed the need for information regarding the population dynamics of Chesapeake Bay sheepshead by investigating their age distribution, growth rate and reproductive biology. We used this information to construct yield-per-recruit models, which local management agencies may use in the formation of scientifically based management measures. We collected samples from 2006 to 2009 from both fishery-dependent and fishery-independent sources. Based on the age and growth analysis, we determined that Chesapeake Bay region sheepshead were living to a maximum of 35 years old, or 12–21 years older than previously reported for sheepshead, and were on average larger-at-age and attaining larger maximum sizes than their more southern counterparts. These drastic differences in age and growth leads to the distinction of Chesapeake Bay region sheepshead as a distinct population from sheepshead found south of Cape Hatteras. Despite these differences in age and growth, analysis of Chesapeake Bay region sheepshead reproductive biology reveals little difference from the reproductive biology of sheepshead found south of Cape Hatteras, with all sheepshead being non-hermaphroditic batch spawners, exhibiting early maturation by age 2, and a spawning season occurring from the late winter through the spring. When we integrate the information on age, growth and reproductive biology into a Beverton-Holt yield-per-recruit (YPR) model, results suggest YPR can be maximized by setting age of recruitment to the fishery to 7 years of age, corresponding to a 483 mm (19 in) minimum length limit, resulting in a maximum YPR of between 1.2 to 1.7 kg. This time of recruitment to the fishery and potential maximum YPR is 2–5 years older and 0.6–1.5 kg greater than suggested when we use age and growth data from other regions in the same Beverton-Holt YPR model.

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DOI

10.25777/7gs8-1d62

ISBN

9781124664033

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