Date of Award

Summer 2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Committee Director

John R. McConaugha

Committee Member

Alexander Bochdansky

Committee Member

Lisa Horth

Abstract

The Chesapeake Bay blue crab, Callinectes sapidus, is an important species both ecologically and as a fishery. Fishery dependent and independent data indicate that the population declined abruptly in the mid-1990s and has remained low. Previous work prior to the decline in population abundance found a significant relationship between size and fecundity for mature females. As with many heavily fished populations, this population has experienced a reduction in the size at maturity. The objectives of this study were to reassess the fecundity of the population, determine the lipid and protein energy allocated for reproduction, and to examine the concentrations of lipid fractions in eggs.

This study indicated that the size-fecundity relationship is absent or very weak. Fecundity estimates indicate that individual female fecundity has decreased by an order of magnitude from previously reported values. Egg production varied both inter- and intra-annually with a greater number of smaller eggs produced later in each season. This all suggests that allometric regulation is no longer the primary factor determining egg production in this population.

Negative changes in the allocation or availability of energetic resources may be having a significant impact on this population. Lipid and protein concentrations measured from the hepatopancreas, ovaries and eggs of mature female blue crabs demonstrated that first brood production is derived from stored resources in the hepatopancreas. Later brood production is likely allocated for directly from ingested food. Egg lipid and protein concentrations showed considerable inter- and intra-annual variation, suggesting that there were trade offs between lipid and protein allocation. Concentrations of lipid fractions (triglyceride, phospholipid, and cholesterol) also showed variation within and between spawning seasons suggesting significant differences in egg quality.

Decreases in population fecundity in conjunction with observed variation in the biochemical content of eggs can have far reaching impacts on the population including larval survivability and recruitment. My results suggest that there are significant shifts in maternal effort, and potentially reproductive success, both inter-annually and seasonally. Fluctuations in energy available to an embryo, as well as the production of fewer embryos have significantly lowered the reproductive output of this population.

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DOI

10.25777/enqx-pb23

ISBN

9781109368765

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