Blue crab larval dispersion and retention in the Mississippi Bight
Abstract:A conceptual hypothesis relating physical forcing to dispersion and retention was developed for blue crab larvae within the Mississippi Bight. The spawning period for blue crabs in the northern Gulf of Mexico is protracted. Hatching of eggs occurs near the barrier islands and mouths of coastal bays from March through October. Larvae are released on ebbing tides and spend the next 30 to 50 d offshore where they develop through seven zoeal stages before undergoing metamorphosis to megalopae. Duration of the megalopal stage is variable but generally persists from 6 to 20 d. Blue crabs recruit to Gulf estuaries as megalopae. During the critical planktonic phase in their life history, larvae are subject to the vagaries of seasonal circulation patterns which can either return them to nearshore where they can successfully settle, or lose them at sea. Archived currents from a 3-dimensional, primitive equation, sigma-coordinate model of the Gulf of Mexico, driven by climatological winds and damped to surface salinity and temperature, were used to study advection of blue crab larvae in the Mississippi Bight. Data suggest that seasonal circulation patterns driven by average wind stress provide a window of opportunity for blue crab larval dispersion offshore and return nearshore during the appropriate period in their development for settlement as megalopae. In the Mississippi Bight, this window usually occurs between April and October. Large basin-scale events, such as Loop Current intrusions and spin-off eddy generation, may interrupt this circulation pattern and change the settlement success rate. Variations in the seasonal forcing, due to anomalous winds, or basin-scale events may contribute to fluctuations in levels of harvestable adult blue crabs.
Document Type: Research Article
Publication date: 1999-07-01
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