Date of Award

Spring 1982

Document Type


Degree Name

Doctor of Philosophy (PhD)


Ocean/Earth/Atmos Sciences



Committee Director

Anthony J. Provenzano, Jr.

Committee Member

John McConaugha

Committee Member

Phil Mundy

Committee Member

Ronald E. Johnson

Committee Member

Ray Alden


Twenty-one stations forming a transect of the Pamunkey River, York River, lower Chesapeake Bay and adjacent coastal waters were sampled from July through September 1980. The megalopa stages of 11 brachyuran species were sampled. Vertical and horizontal distributions are described for each species in relation to salinity and water column stratification. The megalopae are assigned to three apparent recruitment strategies: retained estuarine, expelled estuarine and retained coastal megalopae. the megalopa stages of estuarine adults, such as Hexapanopeus angustifrons, Neopanope sayi, Panopeus herbstii and Pinnotheres ostreum, are retained in estuarine epibenthic waters, while Rhithropanopeus harrisii are retained in slightly shallower estuarine waters. The larvae of some estuarine species such as Callinectes sapidus, Uca spp. and Pinnixa sp., are expelled from the estuary, resulting in maximum megalopal abundances on the shelf. Differences in vertical distribution, distance from the bay entrance and the proportion of the catch within the estuary suggest the megalopa is important in reinvasion of the estuary for Uca spp. and Pinnixa sp., but facultatively reinvasive for Callinectes sapidus. Two shelf species, Portunus sp. and Cancer irroratus are most abundant in the neuston of shelf waters and thus their dispersal to the estuary is impeded.

Another shelf form Libinia spp., is commonly found as an adult in the lower Chesapeake Bay. Although their megalopae are most common in the epibenthos on the shelf, 9% are found in the bay.

All megalopae displayed a strong tendency to be distributed either above or below a pycnocline, when present. Five species show significant shifts in vertical distribution between stratified and homogeneous water columns. No evidence of decreased dispersal is found for increasingly estuarine species.