ABSTRACT
Red Snapper, Lutjanus campechanus, is a demersal, nonmigratory, continental-shelf species with strong site fidelity yet an extensive latitudinal habitat range. Directly coincident with this range is the western boundary current system in the warm temperate North Atlantic Ocean, suggesting that Red Snapper range may be linked by larval dispersal. Information regarding the balances between natal retention of pelagic larvae and broad dispersal along the boundary current is fundamental to understanding variation in population abundance by natural causes. The Gulf of Mexico has a large population of Red Snapper and a long history of oceanographic observations and oceanic current modeling. In the present study, this history of 8current modeling was reviewed to examine possible connections of Red Snapper populations through larval drift within the distributional limits of Red Snapper. Ocean current dynamics, driven by climatological processes, may affect larval dispersal and regional differences that occur in the Gulf of Mexico. For Red Snapper, connections were relatively weak across the Gulf of Mexico basin but sufficient to allow genetic mixing. In the southern Gulf of Mexico, the relatively large production of Red Snapper larvae on Campeche Bank was predominantly retained on the Bank, with a small portion of these larvae transported by the Loop Current both to the west Florida shelf and into the Florida Current. In the northern Gulf of Mexico, topographic barriers and degree of penetration of the Loop Current with spin-off eddies were important factors for the dispersal of larvae. Topographic features reduced connections between the eastern and western Gulf of Mexico. Eastward larval transport during high spawning months was directed from settlement areas toward deep water. Westward transport facilitates larval dispersal, but this occurred during months when spawning was reduced. Energetic Loop Current spin-off eddies negatively affected highly fecund Red Snapper populations on the outer shelf west of the DeSoto Canyon. Dispersal to the deep basin in the Gulf of Mexico was high and variable, while larval redistribution to suitable settlement habitat was weak. Ocean current modeling indicated that the more abundant Red Snapper population in the western Gulf of Mexico did not contribute substantially to stocks east of the Mississippi Delta. Also, there were areas of strong natal retention despite wide larval dispersal, but substantial loss to the deep basin over much of the Gulf of Mexico. The overall picture in the Gulf of Mexico was one of weakly connected populations with scales of roughly 100–200 km set by hydrography.
