Abstract

The Florida Big Bend region in the northeastern Gulf of Mexico contains both spawning sites and nursery habitats for a variety of economically valuable marine species. One species, the gag grouper (Mycteroperca microlepis), relies on the shelf circulation to distribute larvae from shelf-break spawning grounds to coastal sea-grass nurseries each spring. Therefore, identifying the dominant circulation features and physical mechanisms that contribute to cross-shelf transport during the springtime is a necessary step in understanding the variation of the abundance of this reef fish. The mean circulation features and onshore transport pathways are investigated using a numerical ocean model with very high horizontal resolution (800–900 m) over the period 2004–2010. The model simulation demonstrates that the mean springtime shelf circulation patterns are set primarily by flow during periods of southeastward or northwestward wind stress, and that significant cross-shelf flow is generated during southeastward winds. Lagrangian particle tracking experiments demonstrate that a primary pathway exists south of Apalachicola Bay by which particles are able to reach inshore, and that significantly more particles arrive inshore when they originate from an area adjacent to a known gag spawning aggregation site. The results provide, for the first time, a description of the pathways by which onshore transport is possible from gag spawning sites at the shelf break to sea-grass nurseries at the coast in the Florida Big Bend.

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