Settlement of Callinectes Sapidus Megalopae on Artificial Collectors in Four Gulf of Mexico Estuaries
Abstract:Standardized artificial collectors were used to document trends in settlement of blue crab (Callinectes sapidus) megalopae in four Gulf of Mexico estuaries. Blue crab megalopal settlement was generally episodic within an estuary and asynchronous among coastwide sites. Daily settlement of megalopae at a given site and rankings of total numbers among sites varied greatly from year-to-year. Although spawning is protracted and megalopae are available in offshore waters throughout most of the year, most megalopae were collected during August-October. Limited settlement of megalopae in late spring and early summer occurred in the two estuaries (Galveston Bay in 1992 and Terrebonne Bay in 1991) for which sampling was conducted during this period. Within several estuaries, there were no clear environmental variables that corresponded most closely to peak:events of megalopal settlement. Combinations of equatorial tides and onshore winds (when present) were the most apparent environmental variables correlated with high daily settlement at Mobile Bay mouth. The majority of high settlement events for Mississippi Sound were associated with tropic tides coupled with onshore winds. The relative importance of environmental variables affecting settlement varied from year-to-year in several of the estuaries. Limited coherence between gulf sites was not supported by plausible mechanisms for transport, with the exception of a 2- to 3-d lag from the mouth of Mobile Bay to a mid-estuary site. Inter-regional comparisons of monthly settlement means during peak: settlement months were robust and consistent with regional climatic controls (temperature and salinity) and long-term water level patterns (lunar periodicity and meteorology). Large numbers of blue crab megalopae recruited to gulf estuaries. Numbers of settling blue crab megalopae declined with distance from the Gulf of Mexico, but still recruited in fairly large numbers well into the two estuaries where such data were available.
Document Type: Research Article
Publication date: November 1, 1995
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