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.

This species is a filter feeder that removes particles from the water column, including diatoms, flagellates, cyanobacteria, and other microplankton. Using its pedal, or foot, it can also feed on soil microbes and periphyton (Bolam et al. 2019). Corbicula fluminea is consumed by fish, birds, mammals, crustaceans, and turtles but its thick wide shell makes it less palatable than other unionids (Castro et al. 2018a, Castro et al. 2018b, Bradshaw-Wilson et al. 2019, Sterrett et al. 2020).

Corbicula fluminea is a functional hermaphrodite, and incubates its larvae in gill chambers when waters are >15 C. It can also reproduce by self-fertilization at different ploidy levels, and is capable of androgenesis, a type of male quasi-sexual reproduction (Hsu et al. 2020). The reproduction of C. flumina is very plastic, and it can respond to the onset of ideal environmental conditions by having multiple consecutive spawning events (Cao et al. 2017). The high reproductive potential of this species has garnered estimates that it only takes one individual to start a new population. Corbicula fluminea can live for around 6 years (Li et al. 2017).

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). Corbicula fluminea 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).
 

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

Environmental	Socioeconomic	Beneficial

Realized:
In the Great Lakes, C. fluminea may be restricted to southern areas or near outputs of heated effluent due to intolerance of colder temperatures (Mills et al. 1993; Trebitz et al. 2010), potentially reducing their ecological impact. Elsewhere in the U.S., C. fluminea is capable of altering benthic substrates (Sickel 1986) and limiting resource availability for native species (Devick 1991, see below).

Potential:
A variety of studies have demonstrated the competitive ability and ecosystem impact of C. fluminea. Corbicula fluminea may filter a wider range of food sources at a faster rate than native freshwater mussels, which could decrease food availability for other benthic and pelagic species (Strayer et al. 1999; Vaughn and Hakencamp 2001; Atkinson et al. 2010). A number of experiments analyzing the impact of C. fluminea on native bivalves have documented conflicting results, from competitive exclusion to coexistence (see Strayer 1999; Sousa et al. 2005). Corbicula fluminea has a competitive advantage over a native mussel Unio delphinus resulting in a decline in its performance (Ferreira-Rodríguez and Pardo 2017). Corbicula fluminea outcompeted U. delphinus for food resources (Ferreira-Rodríguez et al. 2018a) and negatively impacted the growth, condition, and locomotion of U. delphinus (Ferreira-Rodríguez et al. 2018b). In a Kentucky river, native mussel abundance was also negatively impacted by the presence of C. fluminea (Haag et al. 2021). Experimental ponds infested with Hydrilla verticillata that were treated with Ctenopharyngodon idella (Grass carp) resulted in secondary infestations of C. fluminea likely due to its superior competitive abilities and the loss of habitat for native species (Holbrook et al. 2020). The high thermal tolerance of C. fluminea may allow it to benefit more than native mussels during heat wave mass mortality events due to higher reproductive potential and faster recovery (Ferreira-Rodríguez et al. 2018c).

Cohen et al. (1984) documented a reduction in phytoplankton abundance by 40-60% in a roughly 7 km stretch of the Potomac River, MD, relative to upstream and downstream segments. This was likely due to the very high densities of C. fluminea in this stretch (an increase from 1.2 clams/m² in 1977 to 1,467 clams/m² in 1981) and the high filter feeding rates that were observed (Cohen et al. 1984). Following the introduction of C. fluminea to the Potomac River Estuary, a series of ecosystem-level changes appeared to occur, including increased water clarity followed by growth of fish, bird, and submerged aquatic plant populations, all of which evidently reversed with the decline of C. fluminea populations (Phelps 1994). These observations suggest that C. fluminea is capable of having far-reaching effects on invaded ecosystems. Alteration of substrate habitat by C. fluminea via sediment disturbance and slow shell decay rates may also shift benthic community structures (Ilarri et al. 2019). In four Brazilian reservoirs, sites invaded by C. fluminea where benthic communities were once dominated by soft sediment taxa were instead dominated by an invasive gastropod (Linares et al. 2017).

Corbicula fluminea has the potential to alter nutrient cycles in invaded systems. Microcosm experiments suggest that C. fluminea can increase sediment oxygen uptake, as well as the release of soluble reactive phosphorus, ammonium, and nitrate (Zhang et al. 2011). Bioturbation as a result of its burrowing behavior releases phosphorus, dissolved inorganic nitrogen, and iron from the sediments into the water column (Chen et al. 2016; Coelho et al. 2018). Nutrient enrichment by C. fluminea favors primary production and increased calcium dissolution which can cause a positive feedback loop and increase its invasion success (Ferreira-Rodríguez et al. 2019). Due to its ability to both filter feed and pedal feed, it can alter the abundance of organic matter in the sediment depending on its primary source of food at a given time (Hakencamp and Palmer 1999). Corbicula fluminea may also bioaccumulate toxic substances and transfer them throughout the food web via its feces (Kuehr et al. 2021). It also has a relatively rapid growth and turnover rate, which can increase its influence on energy and nutrient flows in aquatic ecosystems (Sousa et al. 2008). A population in Florida filters enough water to play a significant role in benthic/pelagic biogeochemical coupling by transporting nutrients and metals from pelagic to benthic environments (Patrick et al. 2017). Furthermore, higher levels of nitrogen, ammonia (NH₃), and orthophosphate (PO₄) in feces and pseudofeces, as well as the chemical releases following C. fluminea summer die-offs, could alter nutrient cycling in freshwater systems (Lauritsen and Mozley 1989; Atkinson et al. 2010) and impact water quality and ecosystem dynamics (Novais et al. 2017). High mortality of C. fluminea is a common occurrence in the summer months (Vohmann et al. 2010; McDowell et al. 2017).

Corbicula fluminea has a moderate socioeconomic impact in the Great Lakes.

Potential:
One of the most prominent effects of the introduction of C. fluminea into the United States has been the biofouling of complex power plant and industrial water systems (Isom et al. 1986; Williams and McMahon 1986; McMahon 2000). It has also been documented to cause problems in irrigation canals and pipes (Prokopovich and Hebert 1965; Devick 1991), as well as in drinking water supplies (Smith et al. 1979). Large numbers of C. fluminea, dead and alive, clog water intake pipes, and the cost of removing them has been estimated at about a billion dollars each year in the United States (Pimentel et al. 2000). Juvenile C. fluminea get carried by water currents into condensers of electricity generating facilities, where they attach themselves to the walls via byssus threads, growing and ultimately obstructing the flow of water. They can also increase sedimentation rates within pipes and canals (McMahon 2000). Several nuclear reactors have had to be closed down temporarily in the United States for the removal of Corbicula from the cooling systems (Isom 1986). Isom (1986) has reviewed the invasion of C. fluminea of the Americas and the biofouling of its waters and industries.

In Ohio and Tennessee where river beds are dredged for sand and gravel for use as aggregation material in cement, high densities of C. fluminea have incorporated themselves in the cement, burrowing to the surface as the cement starts to set and weakening its structure (Sinclair and Isom 1961).

Corbicula fluminea has a moderate beneficial effect in the Great Lakes.
Potential:
Corbicula fluminea is the source of a variety of compounds that may have medicinal properties. A protein-bound polysaccharide isolated from C. fluminea effectively inhibited human breast cancer cell growth (Liao et al. 2016) and could be used as an ingredient for functional and medical foods that inhibit diabetes mellitus (Wang et al. 2019). Extracts from C. fluminea had a protective effect on high cholesterol mice hearts (Hsieh et al. 2018) and improved wound healing (Peng et al. 2017).

While not currently applied in the Great Lakes, Corbicula spp. has the potential to serve as a bioindicator for organochloride pesticides (Takabe et al. 2011; Wang et al. 2018)., rare earth metals (Bonnail et al. 2017), and microplastic pollution (Su et al. 2018). Corbicula fluminea’s high filtration rate gives it potential as a bioremediator (Castro et al. 2018) and was cost effective at treating winery (Ferreira et al. 2018) and olive oil wastewater (Domingues et al. 2020).

Corbicula fluminea may prove effective as a restoration tool to increase water clarity (Shen et al. 2020) and quality. In an outdoor mesocosm experiment, C. fluminea was shown to restore macrophyte populations that were decimated by Carassius carassius by increasing water clarity and nutrient availability (Gu et al. 2020). In another study, C. fluminea altered the phytoplankton community structure by reducing phytoplankton biomass which increased water clarity of a eutrophic system (Rong et al. 2021). Corbicula fluminea can also slowly remove nuisance cyanobacteria and could be used as a bioremediation agent (Silva et al. 2020). In a laboratory setting, C. fluminea reduced E. coli levels below detection limits after 6 hours and underwent depuration after 48 hours, making it a suitable alternative to traditional ozonation and photocatalytic oxidation techniques (Gomes et al. 2018). Silverman et al. (1997) found that C. fluminea are capable of filter-feeding E. coli and other bacteria at a higher rate than some native unionid mussels while Ismail et al. (2018) found that the native California bivalve Anodonta californiensis was equally effective at reducing E. coli concentrations as C. fluminea.

Corbicula fluminea is consumed mainly by fish and crayfish. An account of the species that prey on C. fluminea in the United States is given by McMahon (1983). Garcia and Protogino (2005) describe the diet of some native fish species from Argentina (Rio de la Plata) previously not known to feed on C. fluminea. After C. fluminea became established, several of these fish species modified their diet to feed on C. fluminea and other molluscan invaders.

The presence of C. fluminea shells in otherwise soft substrate has been correlated with an increase in arthropod and mayfly (Caenis spp.) densities (Karatayev et al. 2005; Werner and Rothhaupt 2007, 2008). In one experiment, the effect of the presence of three types of C. fluminea (fed individuals, starved individuals, and shells) on ten other species of invertebrates was tested, and the authors found that no species avoided live individuals or shells of C. fluminea when choosing a substrate (Werner and Rothhaupt 2008). Most taxa preferred sand habitat with C. fluminea shells, supporting the hypothesis that these shells add structural heterogeneity that is conducive to macroinvertebrate biodiversity (Werner and Rothhaupt 2008). Those benthic invertebrates that showed a preference for substrate with living C. fluminea, particularly gastropods, appeared to take advantage of the pseudofeces produced by C. fluminea as a food source (Werner and Rothhaupt 2008). Similarly, C. fluminea proved to be an ecosystem engineer in a New Hampshire river and had either no effect or a slight positive effect on native benthic macroinvertebrate communities (Richardson 2020).

This species is not on the Illinois Aquatic Life Approved Species List and is illegal to be imported or possessed alive without a permit (515 ILCS 5/20-90). It is prohibited in Indiana, making it illegal to import, possess, or release this species into public or private waters (312 IAC 9-9-3). It is prohibited in New York and cannot be knowingly possessed with the intent to sell, import, purchase, transport or introduce nor can any of these actions be taken (6 NYCRR Part 575). This species is listed as invasive in Pennsylvania, however, no specific regulations are defined (Pennsylvania Field Guide to Aquatic Invasive Species- 2015 EditionLink). It is a prohibited species in Wisconsin and one cannot transport, possess, transfer, or introduce this species without a permit (Chapter NR 40, Wis. Adm. Code).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
 

Control
Eradication of Asian clams from infested open waters is unlikely – emphasis is generally on preventing further spread.

Biological
The palatability of C. fluminea to fish and crustaceans is low relative to other bivalves, thus biological control is unlikely in the Great Lakes (Ferreira-Rodríguez et al. 2016; Pereira et al. 2016; Meria et al. 2019). Some species of catfish (Ictalurus furcatus and Silurus glanis) known for their diverse diets do commonly consume C. fluminea, however they are also not native to the Great Lakes (Schmitt et al. 2019; Conéjéro et al. 2020).

Physical
Screens and traps are commonly employed to prevent Corbicula colonization of water intakes (GISD 2013). Diver assisted suction removal and bottom barriers are being researched as potential methods for physical control of Corbicula populations in Lake Tahoe (UC Davis TERC 2004). Benthic barriers have been demonstrated to be effective for short-term control of Corbicula fluminea, but non-target mortality to other benthic invertebrates may be high (Wittmann et al, 2012). Alternatively, small filters can be effective at removing veilgers (Schall 2019).

The inability for C. fluminea to survive extreme temperatures can be exploited as a control mechanism. Immersion in hot water (>45?) for five minutes or direct steam exposure for 30 seconds yielded high mortality of C. fluminea (Coughlan et al. 2019a). Burning exposed clams with a ~1000? flame torch resulted in mortality in three seconds. When clams were buried in sediment, mortality occurred after 5 minutes (Coughlan et al. 2019b). Disrupting substrates prior to hot (steam/flame) and cold shock (dry ice) treatments was shown to increase effectiveness (Coughlan et al. 2021). Desiccation of C. fluminea at 25? resulted in 100% mortality after 48 hours (Guareschi and Wood 2020).

Chemical
A wide array of chemical molluscicides are available, but are not species-specific and may harm native species to a greater extent than non-natives. Corbicula fluminea has a greater tolerance to many biocides than other organisms (fish and invertebrates) and has mechanisms to limit exposure (valve closure, burying) making nonspecific biocides even less effective. Some work has been done to find synergistic combinations of biocides to prevent non-target effects, but a successful product has yet to be discovered (Silva et al. 2016).

Molluscicides are typically classified as either oxidizing or non-oxidizing compounds. Oxidizing chemicals include chlorine, chlorine dioxide, chloramines, ozone, bromine, hydrogen peroxide, and potassium permanganate. Non-oxidizing chemicals (including organic film-forming antifouling compounds, gill membrane toxins, and nonorganics) can be classified into several distinct groups: quanternary and polyquaternary ammonium compounds; aromatic hydrocarbons; endothall as the mono (N,N-dimethylalkyl amine) salt; metals and their salts (e.g., copper sulfate formulations); and niclosamide (including some formulations of Bayluscide). Bayluscide was initially developed as a sea lamprey larvicide, but has molluscicidal activity. While some of these products are biodegradable, many require detoxification or inactivation to meet state and Federal discharge requirements (USACE 2012). Low concentration of chlorine or bromine will kill juvenile C. fluminea (GISD 2013). Elevating pH to 12 with NaOH had 99% lethal exposure in 209 hours (Barenberg and Moffitt 2018).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

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).