Crustaceans (A. J. Benson)

In the Southeast region, there are at least 33 nonindigenous species of crustaceans that have been introduced into freshwater as well as marine ecosystems (Table 1). Freshwater organisms include several species of crayfish, a freshwater prawn, and a daphnia. The marine organisms include barnacles, crabs, shrimps, amphipods, isopods, and tanaids.

Crayfish are the largest contributor of nonindigenous aquatic species in freshwater systems of the Southeast.  Ten species have been introduced outside their historical native ranges. The most notable being the red swamp crayfish, Procambarus clarkii, which has been introduced in Georgia, North Carolina, South Carolina, and Virginia (Hobbs 1989). It is native to the south-central part of the US.  Its introduction is probably the result of either aquaculture escapes or bait bucket releases as are most of the crayfish introductions.  Burrowing activities of the red swamp crayfish can cause damage to water control structures such as earthen dams and levees. It can also be a pest in rice agriculture.  On the positive side, they will feed on snails that often are vectors for human pathogens (Hobbs et al. 1989).   Another crayfish that may be of concern is the virile crayfish, Orconectes virilis.  This species is native to the northern section of the US and has been introduced into Alabama, Mississippi, Tennessee, and Virginia (Hobbs 1989).  It may be impacting aquatic macrophytes and displacing native crayfish.

There is one species of daphnia, Daphnia lumholtzi, which has spread quickly since its discovery about 1990. It is native to tropical and subtropical freshwater lakes in east Africa, east Australia, and the Asian subcontinent of India (Havel and Hebert 1993).  The most distinguishing characteristics of this daphnia are the long helmet and tailspines. The helmet is spine is normally as long as the body length. Other distinct characteristics are the fornices that extend to a sharp point instead of being rounded and the ventral carapace margin, which has approximately 10 prominent spines (Havel and Hebert 1993).

Daphnia lumholtzi has been detected in 56 reservoirs in the southern and mid-western United States. The earliest record is from Texas in 1990 (Havel, pers. comm.). It has since been found in localized waters leading into major river drainages such as the: Arkansas, Cumberland, Illinois, Mississippi, Missouri, South Atlantic-Gulf, Tennessee, and Texas-Gulf. Known occurrences of D. lumholtzi in the Southeast are in the following waters: Guntersville Lake (Tennessee River) in Alabama, Lake Dardanelle (Arkansas River) in Arkansas, Lake Okeechobee in Florida, Kentucky Lake (Tennessee River) in Kentucky, Atchafalaya River in Louisiana, Sardis Lake (Tallahatchie River) in Mississippi, Lake Norman (Catawba River) in North Carolina, Lake Wylie (Catawba River) in South Carolina, and Norris Reservoir (Clinch River) in Tennessee.

It is uncertain how D. lumholtzi was introduced into the U.S. It is suspected that it may have been transported with shipments of Nile perch from Lake Victoria in Africa where it is a dominant zooplankter. Nile perch were originally introduced into Texas in 1983 (Havel and Hebert 1993). The continuing discovery of D. lumholtzi in new locations could be due to contaminated stockings of fish through international commercial trade. At the same time, the close proximity of affected reservoirs in Missouri and in Texas might lead to the conclusion that D. lumholtzi may have spread by recreational fishing and boating from the initially infested reservoirs.

Daphnia lumholtzi is well established and has been collected for several consecutive years in Norris Reservoir, part of the Tennessee River system in Tennessee. Any impacts of this invader are not yet known. Presently, one study indicates it does not appear to be displacing other daphnia in Norris Reservoir (Goulden et al. 1995). However, it could become a dominant zooplankter because of its many tailspines being a deterrent to predators. Stomach samples of fish from Norris Reservoir contained no D. lumholtzi (Goulden et al. 1995).  It is most likely that D. lumholtzi has become a successful invader because of its ability to avoid predation, not because it is a better competitor for the available food supply. Because of its rapid widespread introductions, D. lumholtzi may become a dominant zooplankter in the southern U.S. (Havel et al. 1995).

The marine species are more diverse and include six crabs, five shrimps, three barnacles, four isopods, two amphipods, and one tanaid. Nearly all the marine species are foreign to North American waters and were introduced by either ship hull fouling or ballast water dumping (Table 2). Several crabs species were suspected to have arrived in more unusual pathways such as hiding under the bark of cedar trees imported from Mexico, in interstate shipments of seed clams for culturing, and intentional stocking to create a new fishery.

Impacts vary greatly in the marine environment.  Barnacles are notorious biofoulers of most any substrate, especially man-made structures such as bridges, docks, seawalls, and industrial water intakes. There is the threat of several diseases with the introduction of nonindigenous shrimp. Shrimp farms in Texas and South Carolina have suffered high mortalities because of one of these diseases known as Taura Syndrome. Fortunately, this disease has not been detected in wild stocks in the U.S.   Information on the impacts of some of the smaller organisms like the amphipods and isopods is hard to find or does not exist.

Mammals (A. J. Benson)

The nutria, Myocastor coypus, has been a long time resident of the southeast region. This semi-aquatic, beaver-like rodent is established in all of this region's states except for Kentucky and South Carolina. Populations may be on the increase in Alabama, Arkansas, North Carolina and Tennessee. Surprisingly, nutria occur on over one million acres of land managed by the National Wildlife Refuge system (Bounds 2000).  We can assume that much of that land is in this region because nutria occur in only seven other states not in the Southeast. This voracious herbivore is capable of causing extensive damage to native wetland plants, reducing food and cover for migratory waterfowl, degrading water quality, displacing muskrat populations, and encouraging the spread of purple loosestrife (Bounds 2000).

Literature Cited

Bounds, D. L. 2000.  Nutria: an invasive species of national concern. Wetland Journal 12(3): 9-16.

Goulden, C. L., D. Tomljanovich, D. Kreeger, and E. Corney. The invasion of Daphnia lumholtzi Sars (Cladocera, Daphniidae) into a North American reservoir. Pages 9-38 In: Hamilton, S.W., D.S. White, E.W. Chester, and A.F. Scott (eds.). 1995. Proceedings of the sixth symposium on the natural history of the lower Tennessee and Cumberland River Valleys. The Center for Field Biology, Austin Peay State University, Clarksville, Tennessee.

Havel, J. E., and P. D. N. Hebert. 1993. Daphnia lumholtzi in North America: another exotic zooplankter. Limnol. Oceanogr. 38:1837-1841.

Havel, J. E., W. R. Mabee, and J. R. Jones. 1995. Invasion of the exotic cladoceran Daphnia lumholtzi into North American reservoirs. Can. J. Fish. Aquat. Sci. 52: 151-160.

Hobbs, H. H., Jr. 1989.  An illustrated checklist of the American crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Contributions to Zoology 480.  236 pp.

Hobbs, H. H. III, J. P. Jass, and J. V. Huner. 1989.  A review of global crayfish introductions with particular emphasis on two North American species (Decapoda, Cambaridae). Crustaceana 56(3):299-316.

Table 1. Crustaceans introduced into states with
U.S. Fish and Wildlife Service Region 4. - click to enlarge

Table 2. Year first documented, origin, pathway of introduction,
and status of crustaceans introduced into states in Region 4. - click to enlarge

CARS / Cover / Back / Next