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CSIRO Marine and Atmospheric Research
Past Seminars

Seminar Abstract

Observing and Modelling the Spawning Migration of the Blue Crab Callinectes sapidus

Adult blue crabs (Callinectes sapidus) live primarily in estuaries, while their larvae develop as zooplankton in offshore waters. For larvae to reach suitable offshore development areas, female blue crabs migrate from adult habitats in the upper estuaries to regions near the ocean to release larvae. During the latter part of this migration, ovigerous crabs use ebb-tide transport, a vertical migratory behavior in which crabs swim up into the water column during ebb tides, to move seaward to larval release areas. To determine the relationship of ebb-tide vertical migrations to local currents and the influence of these vertical migrations on the transport of blue crabs in the estuary, ovigerous females with mature embryos (~ 1 - 3 days from hatching) were tracked near Beaufort Inlet, North Carolina, in July and August 2001 and 2002. Crabs were tagged and tracked using ultrasonic telemetry, and currents near the crabs were measured simultaneously with a shipboard acoustic Doppler current profiler.

To gain further insight into the ovigerous blue crab spawning migration, the results of the tracking study and additional laboratory and field studies were used to create a behavioral model of ovigerous blue crab ebb-tide transport. This model was incorporated into a particle-tracking algorithm driven by velocity fields from a numerical circulation model of the Beaufort Inlet region of North Carolina. With this coupled model, the trajectories of migratory ovigerous crabs in the region were simulated and used to determine: 1) the spatial extent of successful starting locations (i.e., where in the estuary ovigerous crabs need to begin their migration to reach coastal areas suitable for larval release within the migratory period), 2) the sensitivity of migratory success to crab activity level (i.e., how active crabs are) and starting time in the tidal-diel and spring-neap cycles, 3) migratory speeds in the estuary, 4) migratory residence times in the estuary, and 5) likely larval release locations.

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Peter Oke, (Oceanographic seminars) CSIRO Marine Research (03) 6232 5387
Keith Hayes, (Biological seminars) CSIRO Marine Research (03) 6232 5298
Katrina Nitschke, Antarctic Climate and Ecosystems CRC (03) 6226 2265 & IASOS, University of Tasmania (03) 6226 2509