Chesapeake Bay Introduced Species Database

Corbicula fluminea

Common name(s):
Asian Freshwater Clam
The Asian Freshwater Clam Corbicula fluminea is native to Asia, Indonesia, Philippines and probably Africa and Australia. It was introduced in western North America by Chinese immigrants as food before 1924. It is now found throughout the Pacific, Mississippi, Gulf, Great Lakes, and Atlantic drainages. Its rapid spread suggests that there were multiple introduction pathways and entry points including ballast water, canals, fisheries, and the aquarium fish-bait trades. It arrived in the Chesapeake Bay watershed in the 1970s and is now very common in most freshwater tributaries. The introduction of such a rapidly reproducing filter-feeder has increased water clarity and provided a new food resource, but may also have far-reaching effects on food webs, nutrient and organic material transport to lower parts of the Bay, and on migratory birds and fish. In areas with high population densities they compete for food and space with native freshwater mussels.
Image courtesy of Image courtesy of United States Geological Survey, via Wikimedia Commons public domain license. .

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Environmental Tolerances

For Survival
For Reproduction
Temperature (ºC)
2 34 18 30
Salinity (‰)
0 13 0 2
null null    
Salinity Range

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Age and Growth

Minimum Adult Size (mm)
8 13.4
Typical Adult Size (mm)
20 20
Maximum Adult Size (mm)
60 60
Typical Longevity (yrs)
1 1
Maximum Longevity (yrs)
4 4

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Reproductive Season
May --- January
Typical Number of Young
per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
outcross-external; self-internal
More than One Reproductive
Event per Year
Reproductive Strategy
Egg/Seed Form

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Minimum Typical Maximum
Egg/Seed Development Time (days)
null 30 null
Larval/Seed Development Period (days)
null null null
Male Maturation Age (yrs)
0.08 0.25  
Female Maturation Age (yrs)
0.08 0.25  
Larval/Seed Form  
planktonic; direct develop

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Locomotion and Abundance in Chesapeake

planktonic; mobile abundant
sedentary abundant
sedentary abundant

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Habitat Preferences

Primary Horizontal Habitats
nontidal freshwater; unstructured nontidal freshwater; unstructured; grass beds nontidal freshwater; fresh (non-tidal) marsh; unstructured; grass beds; fresh tidal marsh
Secondary Horizontal Habitats
null null null
Reproductive Horizontal Habitats
n/a n/a nontidal freshwater; unstructured; fresh tidal marsh; grass beds
Vertical Habitats
epibenthic epibenthic; endobenthic epibenthic; endobenthic
Substrate Type
sand; vegetation; none silt; clay; mud; sand; gravel; vegetation silt; clay; mud; sand; gravel; vegetation
Tidal Height Location
subtidal subtidal subtidal; low intertidal
Wave Exposure
moderate; low; protected
Water Flow
stagnant; slow; fast

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Trophic Interactions

Trophic Status
suspension feeder suspension feeder suspension feeder
Common Food/Prey Items
phytoplankton; detritus phytoplankton; detritus phytoplankton; detritus
Common Competitors
freshwater bivalves (Unionidae; Sphaeridae); Musculium partumeium; Pleurobema collina; Elliptio masoni; Alisomodonta undulata; Strophitus undulatus; other spp.; Rangia cuneata; zooplankton freshwater bivalves (Unionidae; Sphaeridae); Musculium partumeium; Pleurobema; Elliptio masoni; Alisomodonta undulata; Strophitus undulatus; other spp. ; Rangia cuneata; zooplankton
Common Consumers
Fish - Lepomis macrochirus; Lepomis microlophus; Lepomis megalotis; Acipenser sp.; Cyprinus carpio; Ictalurus punctatus; Ictalurus furcatus; Procambarus clarkii; Cambarus bartonii; ducks (Aix sponsa; Anas clypeata; Anas acuta; Anas platyrhychos; Anas rubripes); otters muskrats; raccoons; otters

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Life History: Environmental Tolerances: Temperature- Short term limits for survival of Corbicula fluminea are ~40 C, but for long-term survival, with acclimation at 5-30 C, upper LD 50's (50% Lethal Doses) are 24-34 C (McMahon 1983). The lower limit for most populations is 2 C, but some populations (NE, CO) seem to have survived in colder locations, suggesting acclimation. However, many northern populations are prone to winter die-offs. 'Though observations suggest that this invading species has become established in numerous northern environments, these locations are protected from winter temperatures by industrial thermal effluents, usually from power plants '...suggesting that these thermally protected populations may serve as stepping stones in further northern expansion' (Kreiser and Mitton 1995). Salinity- Corbicula fluminea can tolerate gradual increase to 24 ppt and sudden increases to 14 ppt, but the usual limit for reproducing populations is 2-5 ppt (McMahon 1983). Specimens from Hong Kong tolerated salinities up to 13 ppt with little mortality (Morton and Tong 1985). Other, Air exposure - 'In high relative humidities, C. fluminea can survive for as long as 38 days in air, a time span more than enough for it to be carried to the United States by Chinese immigrants as a food source during trans-Pacific boat crossing.' (McMahon 1983).

Reproduction: Reproductive Season, More than One Reproductive Event per Year?- Many populations in the Chesapeake basin and elsewhere have 2 peaks per year in spring and fall. This was true at White's Ferry in the non-tidal Potomac (Kennedy and Heukelem 1985), in the tidal Potomac, Phelps 1994, and in the New River VA, (Ohio River Drainage) (Doherty et al. 1986). However, at at least one site, (Mechum River, VA James River drainage), there was only one spawning peak in July (Hornbach 1992). The dates used are from Kennedy and Heukelem (1985). Typical Number of Young per Reproductive Event- The number of larvae released are highly variable. Examples include: 1050-1900 larvae/clam, New River VA (Doherty et al. 1986); 480-1919 Mechum's River VA (Hornbach 1992). Sexuality Mode(s) - The type of sexual reproduction varies among populations; all United States C. fluminea are simultaneous hermaphrodites, at a Malaysian site they were largely simultaneous hermaphrodites, but protandric (male first, then female) in Hong Kong. However, such variability is not unusual in molluscs (McMahon 1983). Many aspects of reproductive activity and spawning in C. fluminea may be highly site specific (Doherty et al. 1986; Hornbach 1992; McMahon 1983). Fertilization Type(s) - Unfertilized eggs are released to inner demibranchs of the gills, usually fertilized by sperm of other animals inhaled through siphon, but eggs and sperm pass through common ducts, and capacity for self-fertilization also exists (McMahon 1983).

Development: Larval/Seed Form- Two types of larvae are known; one lacks a velum, has well-developed foot and shell, and is best described as a 'benthic juvenile' stage (non-swimming, but can be carried by strong currents). However, planktonic larvae (veligers) have also been reported (McMahon 1983). Both types of larvae can be released simultaneously (Kennedy and Heukelem 1985).

Dispersal and Abundance: Mode(s) of Dispersal - The most common type of larva ( 'benthic juvenile' ) is non-swimming but may be carried by fast currents. Dispersal by birds in mud on feet or feathers, or in the gut, is unlikely over long distances (Counts 1986); Juvenile C. fluminea can attach to floating logs, etc. by byssal (adhesive) threads (Counts 1986; McMahon 1983).
Community Ecology: Habitat Preferences: Primary Horizontal Habitat - If in a lentic (still-water) habitat, Corbicula fluminea is restricted to shallow nearshore waters and well oxygenated sediments. As a result of its preference for lotic (flowing-water) habitats, C. fluminea may not pose as much of a threat to native bivalve species as has been previously suggested, particularly to the many native species which prefer slower waters and can tolerate much lower oxygen concentrations than C. fluminea (McMahon 1983). However, it is now clear that human activites in North American waterways such as stream canalization and dredging are not only detrimental to habitats of native species, but also optimize the environment for C. fluminea by increasing current flow and eliminating the muds and silts (McMahon 1983). Substrate Type- Densities of small C. fluminea decreased sharply after disposal of fluid mud at sites in the James River (Diaz 1994). In Meyers Branch SC, a Savannah River Coastal Plain tributary, C. fluminea was limited to gravel beds and was not found in sand (Leff et al. 1990).

Trophic Interactions: Predators- 'On the whole, such predation does not appear to be sufficient to reduce C. fluminea densities greatly in most North American drainage systems' (McMahon 1983).

This data was last modified on Tuesday, September 13th, 2005.
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