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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: basket clam

Synonyms and Other Names: Asiatic clam, golden clam, good luck clam

IMPORTANT NOTE: The taxonomy of Corbicula species needs further revision. Therefore until then, in this database unless otherwise named, all unidentified species of the genus Corbicula collected in the United States are compiled under one name, Corbicula fluminea.

Taxonomy: available through www.itis.gov

Identification: A small light-colored bivalve with shell ornamented by distinct, concentric sulcations, anterior and posterior lateral teeth with many fine serrations. Dark shell morphs exist but are limited to the southwestern United States. The light-colored shell morph has a yellow-green to light brown periostracum and white to light blue or light purple nacre while the darker shell morph has a dark olive green to black periostracum and deep royal blue nacre (McMahon 1991). Qiu et al. (2001) reported yellow and brown shell color morphs among specimens collected from Sichuan Province in China. The shells of the yellow morphs were straw yellow on the outside and white on the inside; those of brown morphs were dark brown and purple, respectively. Further analyses revealed that the yellow and brown morphs are triploid and tetraploid, respectively.

A separate clonal population of Corbicula has been reported for one location in the Illinois River (Tiemann et al 2017).  Tentatively named Form D, this newest form is pyramidal in shape with weakly elevated ridges; exterior is yellowish-brown with fine rust colored rays radiating out from the umbo; interior is creamy white but the lateral teeth are purple.  Form D has a distinctive nuclear ribosomal DNA genotype, but the mtDNA COI haplotype is identical to Form A.

Distinctive shell features differenetiating Corbicula species and hybrids have been described in Morhun et al. (2022).

Size: < 50 mm shell length

Native Range: The genus Corbicula lives in temperate to tropical southern Asia west to the eastern Mediterranean; Africa, except in the Sahara desert; and southeast Asian islands south into central and eastern Australia (Morton 1986).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: The Asian clam is a filter feeder that removes particles from the water column. It can be found at the sediment surface or slightly buried. Its ability to reproduce rapidly, coupled with low tolerance of cold temperatures (2-30°C), can produce wild swings in population sizes from year to year in northern water bodies. Both yellow and brown morphs are simultaneous hermaphrodites and brood their larvae in the inner demibranchs (Qiu et al. 2001). Furthermore, C. fluminea is able to reproduce by self-fertilization at different ploidy levels, and is capable of androgenesis, a type of male quasi-sexual male reproduction (Hsu et al. 2020). The life span is about one to seven years.

Means of Introduction: The first collection of C. fluminea in the United States occurred in 1938 along the banks of the Columbia River near Knappton, Washington (Counts 1986). Since this first introduction, it is now found in 46 states, the District of Columbia, and Puerto Rico. Corbicula fluminea was thought to enter the United States as a food item used by Chinese immigrants (Hanna 1966) but there is no direct evidence of that. Alternatively, it may have come in with the importation of the Giant Pacific oyster also from the Asia. The mechanism for dispersal within North America is unknown. It is known mostly as a biofouler of many electrical and nuclear power plants across the country. As water is drawn from rivers, streams, and reservoirs for cooling purposes so are Corbicula larvae. Once inside the plant, this mussel can clog condenser tubes, raw service water pipes, and firefighting equipment. Economic problems can result from the decreased efficiency of energy generation. Warm water effluents at these power plants make a hospitable environment for stabilizing populations. With man demonstrated to be the primary agent of dispersal, no large-scale geographic features function as dispersal barriers (Counts 1986, Isom 1986). Current methods of introduction include bait bucket introductions (Counts 1986), accidental introductions associated with imported aquaculture species (Counts 1986), and intentional introductions by people who buy them as a food item in markets (Devick 1991). The only other significant dispersal agent is thought to be passive movement via water currents (Isom 1986); fish and birds are not considered to be significant distribution vectors (Counts 1986, Isom 1986). Migrating blue catfish (Ictalurus furcatus) had shown the potential to pass live adults through their gut when the mussel was consumed and digested in cooler water (<21.1º C) (Gatlin et al. 2013).

Status: Corbicula fluminea is established in river networks across many states as well as in Lake Erie, Lake Michigan, and Lake Superior (USEPA 2008).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health	Other

 

Environmental: The most prominent effect of the introduction of the Asian clam into the United States has been biofouling, especially of complex power plant and industrial water systems (Isom et al. 1986; Williams and McMahon 1986). It has also been documented to cause problems in irrigation canals and pipes (Prokopovich and Hebert 1965; Devick 1991) and drinking water supplies (Smith et al. 1979). It also alters benthic substrates (Sickel 1986), and competes with native species for limited resources (Devick 1991).

Economic: In the USA, C. fluminea has caused millions of dollars worth of damage to intake pipes used in the power and water industries. Large numbers, either dead or alive, clog water intake pipes and the cost of removing them is estimated at about a billion US dollars each year (Anon., 2005). Juvenile C. fluminea get carried by water currents into condensers of electrical generating facilities where they attach themselves to the walls via byssus threads, growing and ultimately obstructing the flow of water. Several nuclear reactors have had to be closed down temporarily in the USA for the removal of Corbicula from the cooling systems (Isom, 1986). In Ohio and Tennessee where river beds are dredged for sand and gravel for use as aggregation material in cement, the high densities of C. fluminea have incorporated themselves in the cement, burrowing to the surface as the cement starts to set, weakening the structure (Sinclair and Isom, 1961). Isom (1986) has reviewed the invasion of C. fluminea of the Americas and the biofouling of its waters and industries.

Ecological: C. fluminea is consumed mainly by fish and crayfish. An account of the different species which prey on C. fluminea in the USA is given by McMahon (1983). Garcia and Protogino (2005) describe the diet of some native fishes from Argentina (Rio de la Plata) previously not known to feed on C. fluminea. Their results indicate that several local fish species have modified their diet to feed on invasive molluscan species such as C. fluminea. A study of sections of a New Hampshire River pre and post-invasion showed that C. fluminea did not have any impact on local invertebrate denisty or biodiverity (Richardson 2020).

Remarks: Factors that may affect population density and distribution of Asian clams include excessively high or low temperatures, salinity, drying, low pH, silt, hypoxia, pollution, bacterial, viral and parasitic infections, inter- and intraspecific competition, predators, and genetic changes (Evans et al. 1979, Sickel 1986). This clam has been found in the stomachs of black buffalo - Ictiobus niger (Minckley 1973); carp - Cyprinus carpio, channel catfish - Ictalurus punctatus, yellow bullhead - Ameiurus natalis, redear sunfish - Lepomis microlophus, largemouth bass - Micropterus salmoides, Mozambique tilapia - Tilapia mossambica (Minckley 1982); blue catfish - Ictalurus furcatus (M. Moser pers. comm. 1996; Gatlin et al. 2013); and spotted catfish - Ameiurus serracanthus (A. Foster pers. comm. 1996). Other predators of Corbicula include birds, raccoons, crayfish, and flatworms (Sickel 1986). Densities of C. fluminea have also been documented to occur by the thousands per square meter, often dominating the benthic community (Sickel 1986).

Though there is considerable morphological variation in C. fluminea, one study showed that it is possible to identify genotypes in populations based on internal shell color (Hsu et al. 2020).

References: (click for full references)

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Counts, C.L., III. 1985. Corbicula fluminea (Bivalvia: Corbiculidae) in the state of Washington in 1937, and in Utah in 1978. Nautilus 99:18-19.

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Other Resources:
 

Corbicula fluminea (Global Invasive Species Database)

Great Lakes Waterlife

 

US Fish and Wildlife Service Ecological Risk Screening Summary for Corbicula fluminea

Author: Benson, A., Foster, A.M., Fuller, P., Constant, S., Raikow, D., Larson, J., Fusaro, A., and A. Bartos.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.