Settlement of blue crab megalopae along the Gulf Coast

The Gulf of Mexico effort in the cooperative, inter-regional blue crab settlement program began in 1990 and continues to present with as many as four sites, each with at least two years of data. Sites are Galveston Bay TX, Terrebonne Bay LA, Mississippi Sound MS. and Mobile Bay AL. Peak settlement episodes on artificial substrates in surface waters of Gulf coast estuaries range from the 10s to 1000s per collector; these values are two to three orders of magnitude greater than those for the East coast. Peak megalopal settlement generally occurs in Aug-Oct in Gulf coast estuaries, but varies from year-to-year. Megalopal settlement is asynchronous among Gulf sites, and is mostly episodic. Settlement peaks in Gulf study sites either (1) show no clear pattern with lunar periodicity or winds, (2) are consistent with onshore winds, or (3) show clear synchrony with lunar periodicity at the time of the new moon. In contrast, settlement peaks along the East coast are synchronous with large-scale climatic and physical forcing