If it were not for a recent report on the introduction of the edible brown mussel (Perna perna) from South America (Hicks and Tunnell 1993), no records of established introduced mollusks in the Gulf of Mexico would be available (Carlton 1992b). The pathway of introduction of this mussel is uncertain. It may have been imported live for sale in the local seafood market or introduced as a fouling organism from the hulls of ships or in the ballast water discharges from the South American vessels that frequently use the nearby harbor. Because the present range of the edible brown mussel is entirely in Texas waters, it will not be further discussed in this publication.
Charru Mussel (Mytella charruena d' Or-bigny, 1846). This species, which is native to Venezuela and nonindigenous to Florida, was found fouling the brackish water intake of a power plant near Blount Island on the St. Johns River in 1986 (Lee 1987). The mussel was first noted on filters at the Northside Generator Plant on the St. Johns River. These 2.5 cm-long mussels occurred in substantial numbers when they were discovered and were of considerable concern to the plant manager. Because tankers from Venezuela frequent the port, the mussel may have been brought in by the vessels as a fouling organism. No recent records of this species being taken in Florida waters could be found. It seemingly disappeared by 1987 (Carlton 1992).
Saber or Mexican Crab (Platychirograpsus spectabilis de Man 1896). In April 1936, the sabre crab was found in Florida's waters during an ecological study (Marchand 1946) of the Hillsborough River, Hillsborough County, from near the mouth and along 16 km of the river, upstream to Sulphur Springs. The crab inhabited shallow water near logs and rocks, and the largest concentration were at the site called "Old Dam" on the Hillsborough River in Tampa. At night, the crabs come out and feed on algae and diatomaceous mats on the submerged rocks and timbers. The crab was probably introduced into the Hillsborough River during the first few months of World War I in 1915, when the Tampa Box Company imported large cedar logs from Mexico. The trees were cut in Mexico and floated down the rivers to the coast, where they were loaded onto ships and later unloaded in large rafts at the mouth of the Hillsborough River near Tampa and floated upstream to a mill station (Marchand 1946). Inquiries of the employees in the mill revealed that they had observed live crabs under the bark and in the cracks in the logs. After the first observations, none was recorded of them being present for many years. The construction of a dam on the Hillsborough River may have prevented the crabs from moving into warmer freshwater springs during the cold winter months, thereby causing the disappearance or decline of the crab. For nearly 40 years, no new observations were reported until the early 1980's, when Gordon Stevens of Riverview, Florida, found the crab and brought it to the attention of Martha Kjeer, a Riverview resident (Flinchbaugh 1984). In 1984, Kjeer and Manny Lopez, a Southwest Florida Water Management District employee, exploring the vicinity of Buckhorn Creek, a spring-fed tributary of the Alafia River, found more crabs. The crab was later identified by Dr. Wayne Price, Marine Biology Professor, University of Tampa (Flinchbaugh 1984) as the sabre crab. No additional recent published information could be found on this species, and its present status is unknown.
Benedict's Wharf Crab (Armases benedicti Rathbun, 1897). This crab is native to Brazil, Guyana, and Surinam, (Rathbun 1918). It was collected only once at Key West, Florida, in 1918 (Gore 1982). Although the species is presently on Florida's Rare and Endangered Biota List, the status of this species is an endangered species or an exotic species that was introduced into Florida and only survived in the Key West area for a short while before disappearing is questionable.
Indo-West Pacific Samoan Crab (Scylla serrata). This crab was purposely introduced into Florida to establish a commercial crab fishery. (D.K. Camp, Florida Marine Research Institute, Department of Environmental Protection, St. Petersburg, Florida, personal communication). The present status of this introduction is unknown.
Jumbo Tiger Shrimp (Penaeus monodon (Fabricius, 1798)). This shrimp is a native to southeast Asia, the Philippines, and Australia. It can reach a length of 26.5 cm and a weight of 150 g. It is one of two species of nonindigenous shrimp that were identified as having aquaculture potential in the coastal areas of the southeastern United States.
The jumbo tiger shrimp can survive in freshwater and in estuarine habitats with salinities of 3-35 o/oo and temperatures of 25-33 C. Licop (1988) discussed the required water quality parameter ranges for culture of the tiger shrimp. Freshwater temperatures must be 28-31 C, sea water temperatures must be 24-31 C with a salinity of 28-33ppt. The other requirements for the culture of this species, including spawning, feeding, culture, and disease control were described in detail (Motoh 1981, Anonymous 1988, Solis 1988). The culture of shrimp in the western hemisphere and its status were described in detail (Hanson and Goodwin 1977).
In 1988, the Waddell Mariculture Center, Bluffton, S.C., which was conducting research education and extension services on this species, had an accidental release from its facility into a stream that terminates in coastal waters. The center had imported 200,000 post-larvae from the Hawaii Department of Aquaculture. The number that escaped is unknown, but approximately 1,000 adults were later recaptured by commercial shrimpers along the East Coast of the United States as far south as Cape Canaveral, Florida. The species has not been taken in recent years and is not believed to be established. There is no indication that any nonindigenous diseases were introduced. The winter water temperatures along the northern Florida coasts are believed to be too cold for the survival of the jumbo tiger shrimp.
Pacific White Shrimp (Penaeus vannamei Boone). The native range of the Pacific white shrimp extends along the west coasts of North and South America from the Gulf of California to Peru (Perez-Farfante 1988). Nonindigenous shrimp have been used in aquaculture in the southeastern United States, including Florida, Georgia, and South Carolina (Rosenberry 1983). The Pacific white shrimp is the second nonindigenous shrimp species with potential for aquaculture in the southeastern coastal United States.
In 1985, many shrimp farms in South Carolina began importing and stocking postlarvae of the fast growing Pacific white shrimp (Sandifer et al. 1988). The species continued to be the shrimp of choice by these farmers (Wenner and Knott 1992). Sandifer et al. (1988) discussed the intensification of shrimp culture in South Carolina. The growing season for shrimp in South Carolina and in other parts of the southern United States is limited to 5-7 months. United States farmers must maximize production during this period. At one time, the pond culture of penaeid shrimp in South Carolina was sizable with at least 18 different privately owned shrimp farms (Wenner and Knott 1992). The present status and history of marine and freshwater shrimp farming in South Carolina and in Florida was summarized by Hopkins (1991). He stated, however, that there has never been a large-scale marine or freshwater shrimp culture in South Carolina that could be considered an economic success. To prevent the escapement of cultured nonindigenous shrimp into the wild, South Carolina adopted a series of terms and conditions for the culture of penaeid shrimp in coastal waters.
However, specimens of the Pacific shrimp, including sexually mature males, were confirmed as present in the commercial trawl fishery in fall 1986 in the mouth of the North Edisto River,S.C. (South Carolina Wildlife and Marine Resources Department 1990). They were probably escapees from culture facilities there is no evidence that the species is established in the area. To document and track the introduction of nonindigenous shrimp into open-water coastal ecosystems in the future, Wenner and Knott (1992) recommended that monitoring be established in the coastal waters of Georgia and Florida.
The wild-caught native shrimp fishery in Florida during 1987 was valued at $50 million (ex vessel; Karen Steidinger, Florida Department of Natural Resources, personal communication). Any introductions of a nonindigenous species or their diseases that threaten this industry should be carefully evaluated.
Commercial cultivation of shrimp in coastal embayments, ponds, and tanks along Florida's coastline was attempted but proved to be uneconomical because of the winter water temperatures. The culture of shrimp in Florida was conducted in small, densely stocked tanks and ponds with rapid circulation and frequent exchange of seawater and heavy feeding with costly pelleted feed. After a few years, the industry moved to Central and South America (Shireman and Lindberg 1985). In that area, the shrimp are raised in extensive systems in larger ponds; sparse natural populations are brought in with the sea water while filling the ponds. Little supplemental feeding is required. Facilities farther south can also produce as many as 3 crops/year and have reduced labor costs (Shireman and Lindberg 1985). Culture of smaller shrimp for bait in the recreational saltwater fishery may develop in Florida.
Winter water temperatures along the northeastern Florida coast are now considered lethal to the Pacific white shrimp and unsuitable for the culture of this species. Nevertheless, concern that nonindigenous shrimp may become established and adversely affect the native shrimp populations continue. This species seemingly has not been released into Florida waters.
The introduction of any nonindigenous shrimp species into the waters of the United States is of much concern, not only because of possible direct effects on the native species if the nonindigenous organism becomes established in Florida's coastal waters but because of the possible introduction of nonindigenous disease organisms as well. Sindermann (1992b,1993) discussed the risk of importing nonindigenous marine species and their pathogens for either aquaculture or for release into the wild to establish new populations. The incidental spread of pathogens with the intentional transfer of species into new areas is a serious problem. These pathogens may be a threat to cultured species and to native shrimp in the surrounding open waters. Several shrimp species in aquaculture in the Southeast carry several disease-causing pathogens (red disease, cramp tail disease), and various bacterial, fungal, and viral infections). These diseases have been spread outside their native ranges and pose a threat to hatcheries and any open waters where the species escape or the effluent is allowed to enter. The virus IHHNV, Infectious Hypodermal and Hematopoietic Necrosis virus, is of particular concern (Rosenberry 1983; Lightner et al. 1989). The Pacific white shrimp is a known carrier of IHHNV and increases the concern for native shrimp populations that may become infected if the virus is introduced. Lightner et al (1989) discussed the concerns about the spread of viruses (IHHN, MBV, and HPV) to native wild penaeid stocks by releases from culture facilities.
