#06–290 October 23, 2006                             

Deep-sea research produces reef maps

Biologists and researchers with the Marine Resources Research Institute of the S.C. Department of Natural Resources and other marine laboratories teamed up with the federal Office of Ocean Exploration to map areas of the outer continental shelf off of South Carolina using high-resolution sonar beams.

The federally funded project included scientists with the S.C. Department of Natural Resources (DNR), Coastal Carolina University and Scripps Institute of Oceanography, and was initiated to learn more about the complexities of the outer continental shelf and upper slope that lies under deep-sea waters of the region. An extensive reef lies in these deep waters off the coast of South Carolina and spans north to North Carolina and south to Georgia. The two-year project specifically aims to determine the distribution of important reef fish that seem to thrive along the deep-sea reef and produce high-resolution imagery to map the detailed features of the reef. Biologists are also interested in assessing the characteristics of this habitat and determining why the areas are important spawning areas for these reef fish, which include species such as tilefish, snowy grouper, red grouper and gray triggerfish.

According to George Sedberry, DNR senior marine scientist and principal investigator on the project, “The aim here is to determine, using sonar, what kinds of bottom habitats that these economically valuable fishes use for important parts of their life history, such as spawning. If we can determine the sonar ‘signature’ of known reef fish spawning sites, we can use rapid, high resolution sonar to quickly find additional habitat that is critical to these important fishery species.”
           
Many of the known spawning areas for the reef fish are in federally proposed Marine Protected Areas, where no bottom-fishing will be allowed. Areas mapped during the Ocean Exploration field study included the preferred alternatives for the northern South Carolina Marine Protected Area and the Edisto Marine Protected Area, which lie between 40 and 50 miles offshore and range in depths from 150 to 550 feet. Areas adjacent to the Marine Protected Areas were also mapped, in order to map the extent of the habitat within and outside of proposed Marine Protected Areas. Extensive reef habitat was found along the edge of the continental shelf. Although fishermen and scientists have known about the existence of this reef, the new maps track its extent along the shelf edge, including its extension well beyond the proposed no-fishing zones. The sonar records indicate an extensive but narrow connected chain of reefs that will remain open to fishing, yet pass through no-fishing zones that will protect part of the population, particularly the large spawning female fish.

The high-resolution sonar maps detail scarp faces and rough reef edges, and illustrate a reef with greater extent than previously mapped. The rapid multi-beam sonar method used has enabled scientists to determine the habitat between well-known and previously mapped patches of reefs, to connect the dots and form a complete picture of some of the shelf-edge reef habitat off South Carolina. The sonar imagery will collectively provide habitat maps for the region and assist future researchers, fishery managers, students and educators interested in features of the ocean floor that are important in producing and sustaining fish and fisheries.