Aquaculture

UGA Shellfish Laboratory

Aquaculture Programs

It is well recognized by most scientists and resource managers that America's fisheries are in serious decline due to overfishing and habitat degradation. As demands for edible fish and shellfish continue to increase, many state and federal agencies now consider aquaculture as the mechanism for the future production of the nation's seafood. Marine aquaculture has been slow in coming to Georgia, but the potential for expansion is virtually limitless and could provide an environmentally friendly economic basis for many of our coastal communities.

Hard Clam, Mercenaria mercenaria
In Georgia clam farming is relatively new with 13 farms in operation, and the vast majority being in McIntosh County. The University of Georgia Marine Extension Service with support from Georgia Sea Grant and the Sapelo Foundation helped to start the industry in the 1990's. In 2004 the fishery was worth half a million and 69,826 pounds of meat was harvested. Farmed clams are recognized as an "Ocean Friendly Seafood" and are a low fat/high protein food, high in calcium and potassium and low in calories, sodium and cholesterol. 2004 saw the first commercial clam farm open in Chatham County, and Liberty County followed suit with two more leases being aquired in 2005. There are two types of lease currently available in Georgia-private and state. The Department of Natural Resources Coastal Resources Division (912-264-7218) maintains these leases. Georgia law (O.C.G.A. 27-4-197) requires that the shellfish operations of the Department of Natural Resources be conducted in compliance with the National Shellfish Sanitation Program. A brochure entitled "Product Safety Guidelines for Shellfish Harvesters" is available to provide guidance for consumer safety.
Currently, there are no clam hatcheries in Georgia and seed must therefore be imported from Florida and South Carolina. Georgia clam farmers are required to plant a larger seed size than farmers in other states. Experimental planting of clams less than 6 mm in size utilizing a variety of grow- out techniques has resulted in 100% mortality. Typically seed are purchased at a size of 8-12 mm and are raised in mesh bags placed on the river bottom. Once they reach a size of 25 mm, they are planted out in bottom plots where they grow until they reach a harvest size of 45 mm. A crop requires approximately 18 months in the field before they reach harvestable size. With funds from the Georgia Department of Natural Resources, we recently developed tidal powered clam nursery systems for growing small inexpensive seed clams up to a field planting size (powerpoint). Further information about the industry can be found in our brochure "Georgia Hard Clam Farming: How to Get Started".

Ark Clams
Ark clams (blood, Anadara ovalis and ponderous Noetia ponderosa) have been attracting attention as candidates to diversify hard clam aquaculture in southern states. In collaboration with the University of Florida and with funding from the U.S. Depertment of Agriculture, and the Florida Cooperative Extension Service we conducted a study on "Diversification for the Hard Clam Aquaculture Industry Through Investigation of Blood Ark and Ponderous Ark Culture and Marketability". Our role was to determine the reproductive cycles and sexual ratios of these species from the east and west coasts of Florida, respectively, through histological analysis of the gonads. Results have been published in the Journal of Shellfish Research. The information provided by these studies will be critical in the development of the hatchery protocol for the species. Information about the nutritional composition, shelf life and the marketability of the species is available on the Florida Cooperative Extension Service Institute of Food and Agricultural Sciences website. Additional investigations have also included the collection of natural ark spatfall as an alternative supply for growers.

Oysters
Georgia once led the nation in oyster landings, most of which was canned. Today the wild fishery is essentially non-existent and mostly serves the local oyster roast trade. There is however, tremendous interest in initiating an aquaculture based industry, which has only been hightened by the recent losses of oyster beds in the Gulf of Mexico. An overabundance of spat, and heavy sedimentation are the main factors precluding success here. A study funded by the Sapelo Island National Estuarine Research Reserve, to develop the optimum foundation and the recruitment and re-colonization rates of oysters is currently underway within the intertidal zone of the Duplin River (Justin Manley, Masters Thesis). Additionally, funding has recently been aquired from the Georgia Department of Natural Resources to conduct culturing investigations using various bags and trays.

Sea Bass
Aquaculture of black sea bass (Centropristis striata) in Georgia appears to have great potential for expansion. A new market has emerged for live black sea bass in the sushi markets of the northeast United States and Canada. Due to increased fishing pressure, regulations have been imposed on C. striata. In an effort to satisfy demand while protecting native stocks we initiated studies to determine optimal grow-out conditions (commercial diet, feeding ration, temperature, and salinity) for growth of hatchery-reared juvenile black sea bass (Chip Cotton, Masters Thesis). Optimal diet was Zeigler Salmon Starter (compared to Nelson and Son’s Silver Cup Salmon Crumbles,Trout Crumbles, and Rangen Trout and Salmon Starter). Optimal daily feeding ration was 5% (compared to 2.5% and 7.5%). Optimal water temperature was 25º C (compared to 15º C, 20º C, and 30º C), and optimal salinity was 20 ppt or 30 ppt (compared to 10 ppt). Additional studies were undertaken to understand the reproductive cycle and document ecto- and internal parasite fauna. Researchers at the Skidaway Institute of Oceanography have also recently designed and tested a recirculating system using greenhouses both for hatchery (grow larval black sea bass to juveniles) and grow out facilities (juveniles to two-pound adults). A low cost biosolar filter system, based on microbial mats and fluidized sand filters, removes ammonia and solid wastes from the fish tanks. Instead of pellets, the black sea bass are fed on live juvenile tilapia, which decreases the amount of solid waste produced resulting in sea water remaining clear. Tilapia are raised in separate tanks with reproduction taking place approximately every two weeks so there is always a ready supply of both tilapia fry and juveniles for the hatchery and grow out facilities. Black sea bass can be raised from larvae to two-pound adults in approximately one year using this system.