The Charleston Bump: An Island of Essential Fish Habitat in the Gulf Stream

The Charleston Bump is a complex bottom feature of great topographic relief located south- east of Charleston, South Carolina. This bottom feature deflects the Gulf Stream offshore in the South Atlantic Bight, and establishes permanent and temporary eddies, gyres, and associated upwellings in the warm Gulf Stream flow. Thermal fronts associated with Gulf Stream deflection, and the bottom feature itself, are believed to be attractive to large pelagic fishes, or result in concentrations of larvae, juveniles, and prey for larger fish. Upwelling in the region supports ear ly life history stages of important fishery species. Deflection of the Gulf Stream may also play a direct or indirect ro le in transport of early life stages toward, or away from, nursery areas. Sea surface temperatures (SSTs) influenced by the Gulf Stream response to the Charleston Bump appear to have a role in determining recruitment success in gag Mycteroperca microlepis, a continental shelf reef fish. Relative cohort strength in gag was correlated (r = 0.89) to SST at 3330N, 7830W. Variability in conditions that affect recruitment of larvae and juveniles, combined with heavy fishing pressure on prespawning adults, may r esult in recruitment failure in gag. In addition to strongly influencing circulation patterns in the South Atlantic Bight, the rugged bottom topography of the Bump is an important habitat and spawning ground for wreckfish Polyprion americanus and supports the U.S. fishery for this species. As a result, the Bump is an essential habitat for this species in U.S. waters. A geographic analysis of commercial pelagic longline logbook data shows that the Charleston Bump is an area of concentrated commercial fishing effort, and that pelagic longline fisheries also concentrate along fronts at the edges of Gulf Stream gyres and eddies downstream. The "Charleston Bump Complex" of rough bottom topography and dynamic oceanography is an essential habitat for wreckfish and highly migratory pelagic fishes, and may influence recruitment success in some continental shelf fishes.