Mapping important fish habitats along the Georgia coast

Beyond the barrier islands of coastal Georgia, the continental shelf extends gradually eastward for almost 80 miles to the Gulf Stream. This broad, sandy shelf largely does not provide the firm foundation needed for the development of reef communities to support recreational and commercial fish species including grouper, snapper, black sea bass and amberjack.

“Natural and artificial reef habitats are important to Georgia fisheries because they provide hard, permanent structure on the Georgia shelf, which is dominantly a vast underwater desert of shifting sands,” said Clark Alexander, professor and director of the University of Georgia Skidaway Institute of Oceanography.  “The Georgia Department of Natural Resources has invested significantly over the past several years in developing the capacity to map these areas to enhance the management of these reef communities."

To increase the availability of high-quality hard bottom areas off Georgia, the DNR began an artificial reef-building program in 1971 to deploy materials at various locations across the continental shelf, from 2 to 30 miles offshore.  Reef materials include concrete slabs and culverts from road, bridge and building demolition, subway cars, ships, barges, and U.S. Army tanks.  Because some of these reefs are far offshore and DNR resources are limited, the status of some of that material has not been examined for decades.

For the past five years, Alexander has been leading an effort to improve understanding of marine, coastal and estuarine habitats and functions using high-resolution sonar to map state water bottoms, with funding from the DNR Coastal Incentive Grant program. Alexander’s team has amassed critical depth and habitat information for five of Georgia’s sounds (Wassaw, Ossabaw, St. Catherine’s, Doboy and Sapelo), revealing deeply scoured areas where underwater cliffs have formed to create hard substrate where complex ecosystems and biological communities have developed.

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Image: Bend of the Skidaway River at Isle of Hope