Subsistence fishing for penaeid shrimp was practiced by coastal native Americans (McKenzie et al. 1981). This practice was passed on to early European settlers and remained a subsistence fishery through the Civil War. Limitations of preservation and transportation of shrimp kept the fishery from developing further than supplying local markets during the seasons when shrimp were available (McKenzie et al. 1980). During the period from the Civil War to the late 1940s, shrimp were primarily marketed as a canned product. As refrigeration and rapid transportation became more available, the emphasis shifted to fresh and frozen product. In 1880, the U.S. Bureau of Fisheries began to record landings of penaeid shrimp in the southeastern US, including South Carolina. The primary method of collecting shrimp during this period was through the use of haul seines and cast nets. In the 1890s, the otter trawl, a cone shaped net pulled behind a boat, was developed and its widespread use began between 1910 and 1920. By the late 1920s, the otter trawl, in conjunction with powered vessels, began to efficiently collect large amounts of shrimp (Commercial shrimp landings 1980-1996 ). Since the late 1950s, neither increased effort nor increased efficiency has significantly increased the overall landings of shrimp in SC. This may indicate that the maximum sustainable yield for this fishery was reached during this period (McKenzie et al. 1980).
Commercial and recreational shrimping has a long history in the ACE Basin and in South Carolina (McKenzie et al. 1980; Low et al. 1996). It is South Carolina's principle fishery, with estimated average commercial and recreational shrimp landings of 2.1 million kilograms (4.6 million pounds) per year. The long history of the use of this resource has resulted in extensive economic and social components to this fishery, with families depending on commercial shrimping for generations. The shrimping industry in the ACE Basin is of primary importance to a number of small coastal communities including Bennett's Point, Edisto Beach, and larger towns such as Beaufort. Not only important to those directly and indirectly involved in the fishery, the presence of the fishing community also contributes to the local tourism-based economy.
Commercial shrimp trawling in South Carolina occurs primarily from Winyah Bay to the Georgia border. Currently, trawling is limited to nearshore areas and some areas just inside the coastal sounds and bays. With an exception during World War II, South Carolina bays and sounds were closed to trawling until the early 1950s to minimize impacts on other recreational and commercial fisheries and to protect shrimp in nursery areas. In the mid-1950s, the Department of Natural Resources, then the Wildlife and Marine Resources Division, opened selected sounds to trawling between August 15 and December 15. Restrictions were placed on trawling in rivers and creeks to minimize the harvest of juvenile shrimp that were generally too small to be commercially valuable (Bearden et al. 1985). Penaeid shrimp use this shallow (0-10 meter), mid-range salinity (8-15 ppt) area as their primary nursery habitat. This habitat is common south of Winyah Bay, which may account for the higher abundance of shrimp in this region when compared to areas north of Winyah Bay (McKenzie et al. 1980). The southern sounds of St. Helena, Port Royal, and Calibogue are among the most productive of the South Carolina estuaries (Bearden et al. 1985).
Three species of penaeid shrimp make up the commercial shrimp fishery in South Carolina. White shrimp (Penaeus setiferus, recently renamed Litopenaeus setiferus) and brown shrimp (Penaeus aztecus, recently renamed Farfantepenaeus aztecus) constitute the bulk of the harvested crop. Pink shrimp (Penaeus duorarum, recently renamed Farfantepenaeus duorarum) is less important.
In South Carolina, trawlers work in nearshore waters from spring to early winter. In 1996, approximately 1.5 million kilograms (3.4 million pounds) of shrimp, including both white and brown shrimp, were landed in South Carolina with an approximate market value of $12.2 million (South Carolina and Colleton County Commercial Shrimp Landings Data ). Trends in Colleton County shrimp landings are similar to yearly state-wide trends . The Marine Resources Division of the SCDNR monitors shrimp population and size, and uses these data to regulate the shrimp fishery.
Penaeid shrimp are also harvested by recreational users, primarily during the fall shrimp baiting season. Total landings, including those by trawling, recreation and aquaculture for the 1994, 1995, and 1996 seasons were approximately 2.7, 4.5, and 2.3 million kilograms ( 6, 10, 5 million pounds), respectively. Recreational landings during 1994 through 1996 ranged from 21 to 23 percent of the total harvest. In addition, there are a number of commercial aquaculture companies in the ACE Basin area (Recreational landings ). Aquaculture landings range from 8 to 19 percent of the total harvest.
The Penaeid shrimp fishery is managed by the South Carolina Department of Natural Resources, Marine Resources Division through licensing and seasonal opening of the fishery. Commercial fishermen must obtain a trawlers license and a captain's license from the Office of Fisheries Management of the SCDNR. The license requires the fisherman to report landings and other fisheries data to the DNR to assist in management of the fishery.
In addition, as of 1997, the SCDNR has authority to open and close the fishery, based on monitoring activities by the DNR. Penaeid shrimp spawn offshore of the southeastern states during late winter and spring. To protect spawning stocks, commercial fishing is not allowed during this period. Trawling for white shrimp generally begins in May but may be delayed to protect spawning stocks. During especially cold winters, with low adult survivorship, opening of the season may be delayed until after brown shrimp spawn in June.
There are a number of problems and conflicts between the shrimp industry and other resource users. These include competition for shrimp between commercial trawlers and recreational shrimp baiters, conflicts with recreational fishermen over the capture of species such as red drum and spotted seatrout, and the destruction of ecologically important live-bottom areas (Bearden et al.,1985; Whitaker pers comm).
Changing Land Use and its Impacts on Penaeid Shrimp
An additional impact associated with agricultural and urban development is the input of pesticides and other contaminants. Scott et al. (1994) have studied the impacts of pesticides on grass shrimp populations in tidal creeks that have agricultural inputs. Many of the pesticides which are used to kill or inhibit insects (arthropods ), are likely to have a similar impact on non-target arthropod species such as shrimp, that utilize the creeks as nursery areas.
Competition Between Commercial and Recreational Shrimping
Impact of Trawling on
Recreationally Important and Endangered Species
Endangered species such as the green turtle, Kemp's Ridley, and the threatened loggerhead sea turtle are a seasonal problem. These species are common during the warmer months and are regularly caught by commercial trawlers. The placing of turtle excluder devices (TED) and reducing the tow time have reduced turtle mortality (McKenzie et al. 1981; Crowder et al. 1995). (See related section: Endangered Species.)
Impact of Trawling on Bottom Habitats
The Shrimp Aquaculture
Extensive vs Intensive Aquaculture
Intensive mariculture operations in the ACE Basin are based primarily on an exotic species of shrimp, the Pacific white shrimp (Penaeus vannamei) that is related to the native white, brown, and pink shrimp. Pacific white shrimp grow to a larger size at faster rates and are more disease resistant in culture conditions than the local shrimp species.
Escapement of Non-indigenous Shrimp
Shrimp Viruses in Aquaculture
The impacts to wild shrimp populations are less clear. The local penaeid shrimp, Penaeus setiferus, has been shown to be susceptible to TSV in laboratory situations (Overstreet et al. 1997). However, there is limited evidence of local wild populations being affected by diseases introduced by aquacultural practices. The limited research on the effects of introduced parasites and diseases on endemic populations of shrimp does not provide a clear indication of the risks involved to wild shrimp populations. In addition to the possibility of introducing viruses through aquaculture, other possible sources of infection include fresh and frozen shrimp imported for the food and bait industries (Browdy and Holland in press), and the release of ballast water from large ships (Carlton 1992). The Marine Resources Division of the SCDNR continues to monitor the quality and status of shrimp farming and the importation of non-endemic species in South Carolina through research and permitting activities.
G. Riekerk, SCDNR Marine Resources Research Institute
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Browdy, C. L. and A. F. Holland. in press. Shrimp virus risk management: A South Carolina Case Study. Aquatic Nuisance Species Digest.
Carlton, J. A. 1992. Marine species introductions by ships' ballast water: An overview. In: M. R. DeVoe (ed.). Introductions and transfers of marine species. South Carolina Sea Grant Consortium, Charleston, SC.
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Stokes, A. 1997. pers. comm. South Carolina Department of Natural Resources, Marine Resources Division, Bluffton, SC.
Turner, R. E. 1977. Intertidal vegetation and commercial yield of penaeid shrimp. Transactions of the American Fisheries Society 106:411-415.
Van Dolah, R., P. H. Wendt, and M. V. Levisen. 1991. A study of the effects of shrimp trawling on benthic communities in two South Carolina sounds. Fisheries Research 12:139-156.
Wenner, E. L. and D. M. Knott. 1992. Occurrence of Pacific white shrimp, Penaeus vannamei, in coastal waters of South Carolina. In: H. R. DeVoe (ed.). Introductions and transfers of marine species. South Carolina Sea Grant Consortium, Charleston, SC.
Whitaker, J. D., L. D. Delancey, and J. E. Jenkins. 1989. A study of the experimental closure of South Carolina's sounds and bays to commercial trawling. Technical Report No. 72. SC Wildlife and Marine Resources Department, Charleston, SC.
Whitaker, J. D. 1997. pers. comm. South Carolina Department of Natural Resources, Marine Resources Division, Charleston, SC.
Perez-Farfante, I. and B. F. Kensley. 1997. Penaeoid and sergestoid shrimps and prawns of the world: Keys and diagnoses for the Families and Genera. Memoirs of the Museum of Natural History 175:1-233.