Using GIS to Investigate the Charleston Bump

The Charleston Bump is a complex bottom feature of great topographic relief located southeast 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 Bump 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 increases productivity that supports life history stages of important fishery species. Deflection of the Gulf Stream may also play a direct or indirect role in transport of early life stages toward, or away from, nursery areas.

South Carolina Department of Natural Resources (SCDNR) scientists use satellite pop-off tags to help determine fish movements. All tagging efforts have taken place on the Charleston Bump. The goal is to learn whether fish stay in the area of the Charleston Bump or go elsewhere. Satellite pop-off tags are small electronic devices that can be attached to large fish such as swordfish, marlin, sailfish, tuna, and sharks. The tags contain electronic sensors that record the depth and water temperature around the fish. They can also monitor light levels throughout the day, and that information can be used to calculate approximate daily positions for the tagged fish. Unlike traditional tagging in which a tagged fish must be recaptured to detect movements, satellite tags transmit the fish's location directly to satellites following pop-up.

Historical studies have confirmed that wreckfish spawn on the Charleston Bump, the only documented spawning ground for this species in U.S. waters. Other fish species, such as the tilefish, blackbelly rosefish, and snowy grouper, also call the Charleston Bump home. The increased productivity associated with the Charleston Gyre results in conditions ideal for development of larvae of fishes that spawn in this area, and this data was used to establish a spawning season closure for the wreckfish fishery there. The fishery is closed from mid-January to mid-April. This closure may have a positive impact on wreckfish fisheries downstream from the Bump.

Since 2001, the National Oceanic and Atmospheric Administration (NOAA) has assisted SCDNR by obtaining sounding data along the Charleston Bump. Both the single-beam and multibeam bathymetry data has been used to create three-dimensional representations of the ocean bottom. These maps are useful in identifying ridges and other areas of interest for potential dive sites. Other data can be overlaid on top of the bathymetry grids to facilitate studies and analyses. SCDNR, Marine Resources Division scientists, and representatives from NOAA and the South Carolina Aquarium have participated in NOAA's Ocean Exploration project during 2001–2004. They traveled to the Charleston Bump on the Seward Johnson II deepwater exploration ship and used the Johnson Sea Link submersible to study the fish and their habitat, learn why they are there, and determine, if possible, the impact of recent commercial fishing.