Date of Award

Spring 1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

John R. McConaugha

Committee Member

Anthony J. Provenzano, Jr.

Committee Member

David L. Feigenbaum

Committee Member

Michael H. Prager

Committee Member

Charles E. Epifanio

Abstract

Larval dispersal and subsequent postlarval recruitment are extremely significant processes affecting the maintenance of ecologically and economically important populations of decapod crustaceans. Vertical positioning in the water column plays a major role in the particular strategies of retention or expulsion with immigration.

The present study was undertaken to investigate variations in vertical distribution according to temporal (diurnal), spatial (estuarine, transition, oceanic), ontogenetic (larval stages, postlarvae) and various environmental factors (especially light, temperature, salinity and tides). Also, effects of vertical positioning on dispersal-recruitment were examined.

Three stations were established for the present study: York River mouth (estuarine) (37°12'N, 76°16'W); Chesapeake Bay mouth (transition) (36°8'N, 76°07'W); Chesapeake Light Tower (offshore) (35°54'N, 75°3'W). Each station was occupied for a continuous 72 hour period in late summer, and quantitative plankton samples were taken every three hours from the following depths: neuston (0.10-0.15 m), 1 m, 3 m, 6 m, epibenthic (10.7-12.8 m).

A total of 41 species, 160 developmental stages and an estimated 6,000,000 specimens were obtained. The most commonly collected species were Callinectes sapidus (87.40% of the total), Uca spp. (3.45%), and Pinnixa chaetopterana (1.74%).

Results indicated that proximity to the estuary greatly affects vertical positioning. Light was proposed to be the major factor affecting distribution, with temperature, salinity and tidal cycles having little effect.

Six dispersal-recruitment patterns were established for collected genera based on vertical and spatial distributions of larvae and postlarvae compared with adult habitats: retained estuarine (Neopanope, Palaemonetes, Panopeus), retained estuarine-transitional (Callinassa, Pinnixa, Pinnotheres, Upogebia), retained transitional-nearshore (Euceramus, Hexapanopeus, Pagurus), retained offshore (Emerita, Libinia, Ovalipes), expelled with estuarine spawning (Uca) and expelled with transitional spawning (Callinectes).

Hypothesized dispersal-recruitment mechanisms included: maintenance at a given depth without diurnal vertical migration, active vertical migration to a depth of zero net motion, and varying degrees of vertical migration throughout the water column.

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DOI

10.25777/h953-fj74

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