The blue crab, Callinectes sapidus, is an estuarine species common in the rivers and tidal creeks of coastal South Carolina (Sandifer et al. 1980). It is one of the primary commercial species statewide, accounting for approximately 10% of the total value of all commercial landings. An average of 2.7 million kilograms (6 million pounds) are landed each year with an overall value of $3-4 million, depending on market prices. The primary commercial method for collecting crabs is by trapping, with minor additional landings from the bycatch of the shrimp trawling industry and through aquaculture operations. The status of the blue crab fishery is continuously monitored by the Marine Resources Division of the SCDNR, using both fishery-dependent and fishery-independent methods.
Blue crabs are an estuarine dependent species, utilizing the tidal creeks and marshes throughout most of their life cycle. Over much of their range, including the entire middle and south Atlantic and Gulf coasts, blue crabs support large commercial trap fisheries. Recently molted blue crabs, called softshell crabs, represent a substantial portion of the fishery in certain locations, but hard crabs make up the vast majority of landings.
Virginian B. F. Lewis' first crab trap, patented in 1928, did not gain widespread popularity because it allegedly allowed crabs to escape too easily. However, his revised trap, patented in 1937, was a big success. During the 1950s, the use of pots (as crab traps came to be known) spread throughout the southeast and Gulf fisheries. Prior to the use of traps, blue crabs in South Carolina were caught using trot lines (Burrell, V.C., pers comm). In general, crab traps consist of a cube of wire mesh with two funnel-shaped openings on opposite sides, a bait well located in the center, and a horizontal divider with openings leading to an upper chamber. Recent innovations include the use of plastic covered wire mesh to retard corrosion, the addition of an iron reinforcing bar at the bottom for stability, and the alternative use of four-funnel traps preferred by some fishermen. Currently, pot fishermen collect the majority of crabs landed on the Atlantic and Gulf coasts. Blue crabs are also the target of substantial recreational fisheries throughout much of their range. Recreational crabbers from Massachusetts to Texas employ a variety of gear types, including crab pots. In South Carolina and in the ACE Basin, it is the primary gear used by commercial fishermen. Pots are set with floats and lines, and they are fished all year round in estuaries along the coast.
The use of trawl nets pulled by medium-sized boats is another method of harvesting blue crabs. In South Carolina, the crab trawling season extends from December through March. This is the second most productive method for the commercial harvest of blue crabs, and it constitutes an important part of the winter catch in the southern part of the state. Some of the state's blue crab harvest is incidental to the shrimp trawl fishery. Crabs caught in this fashion sometimes have sand grains forced into joints in the legs and claws, and may command lower prices than pot-caught crabs.
The softshell crab industry of South Carolina remains under-exploited, but it is of significant value to certain operators. Softshell crab is a popular menu item and because of the difficulty in collecting crab in the softshell stage, command higher prices.
In South Carolina, capture of pre-molt crabs has largely been as incidental catch in the hard crab fishery; however, many of these individuals are damaged by hard crabs present in the pots. Crabbers separate the peelers from the rest of their catch and sell them to dealers who keep them in tanks until they have molted. In South Carolina, it is legal to harvest and process softshell crabs measuring less than 13 cm (5 in). A permit is required by any individual harvesting or transporting them, as does the crab processor.
Certain types of gear are now used to exploit aspects of the crabs' pre-molt behavior (Bishop et al. 1983). Pots that are baited with mature male crabs attract pubertal-molt females. Habitat traps that offer shelter during the softshell stage have also proven effective (Bishop and Burrell 1983). However, the efficiency of gear depends on the availability of the target species, both temporally and spatially. Occurrence of pre-molt crabs may be related to water temperature and lunar phase. Peak capture of soft-shell crab in South Carolina appears to be in April and May, with a secondary peak in late September and early October (Bishop et al. 1984).
The blue crab fishery provides substantial economic benefits to South Carolina, and it must be effectively managed. The agency responsible for this task is the Marine Resources Division of the South Carolina Department of Natural Resources. In South Carolina, it is illegal to take blue crabs whose shell measures less than five inches from tip to tip except for softshell crabs. Pots may only be harvested during the day. Under-sized crabs must be returned to the water alive and in good condition. Females with external egg masses cannot be harvested. Other states allow the harvest of females with egg masses and crabs that are less than five inches. These crabs may be imported into South Carolina and processed, provided a permit for this activity has been obtained. Additional details on the regulations of the blue crab fishery can be found in the SCDNR Marine Fisheries and Related Laws.
The blue crab fishery has remained stable over time. There are no current or historical indications of overfishing. In addition, there are no major conflicts within the commercial pot fishery with respect to competition over fishing grounds, and none that interferes with other fisheries. One problem that has plagued commercial crabbers, however, is theft of their catch or their traps. For this reason, management of the trap fishery has required the attention of law enforcement officials. To catch crabs commercially, a fisherman using three or more traps needs a crabber's license, as well as one for his boat and one for the sale of his catch. For recreational purposes, a person may utilize two traps without the need for a license. As of 1997, it is mandatory that all commercial traps be equipped with escape rings between June 1 and March 14 to allow small crabs to leave the trap. This is to prevent the wasteful killing or injury of animals that have not yet had a chance to reach sexual maturity and reproduce.
Trawling for blue crabs is not allowed during spring months when females migrate to nearshore areas to spawn. This restriction eliminates any conflict with the white shrimp fishery during that time. For trawl harvesting of blue crabs, a fisherman must have a trawling vessel license, a trawler captain's license, and a crab trawl permit.
G. Riekerk, SCDNR Marine Resources Research Institute
Bishop, J. M., E. J. Olmi III, and G. M. Yianopoulos. 1984. Efficacy of peeler pots and experimental habitat pots for capture of premolt blue crabs. Transactions of the American Fisheries Society 113(5):642-654.
Bishop, J. M. and V. G. Burrell Jr. 1983. An experimental habitat pot for premolt crab capture. Journal of Shellfish Research 3(1):82-83.
Bishop, J. M., E. J. Olmi III, J. D. Whitaker, and G. M. Yianopoulos. 1983. Capture of blue crab peelers in South Carolina: An analysis of techniques. Transactions of the American Fisheries Society 112(1):60-70.
Burrell, V. C. 1997. pers. comm. South Carolina Department of Natural Resources, Marine Resources Division, Charleston, SC.
Sandifer P. A., J. V. Miglarese, D. R. Calder, J. J. Manzi, and L. A. Barclay. 1980. Ecological characterization of the Sea Island coastal region of South Carolina and Georgia. Vol. III: Biological features of the characterization area. U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC. FWS/OBS-79/42.