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 Asiatic Clam

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Chris Daphne
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Join date : 2010-01-28
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PostSubject: Asiatic Clam   Mon Mar 01, 2010 1:04 am

Hi All,
Found this and thought it might be of interest

Asiatic clam, Corbicula fluminea

IDENTITY
Taxonomy: Mollusca, Bivalvia, Veneroida, Corbicula fluminea (Muller, 1774).
Quarantine Status: N/A

Description: A bivalve mollusc with a yellowish brown to black shell with concentric, evenly spaced ridges on the shell surface. Adult clams are usually less than 25mm but can grow up to 50 to 65mm in length (Aguirre & Poss 1999).
Signs & Symptoms: N/A

GEOGRAPHICAL DISTRIBUTION
Native Range: Korea, South-eastern China and southeastern Russia, including Ussuri Basin.
Introduced Range: South America (Argentina, Panama), USA (introduced to 38 states and the District of Columbia), Japan, widespread in Europe. England: Invaded in 1998. It remained confined to an isolated network of rivers in Eastern Britain until 2004, when it was discovered in low densities in the River Thames, London.

BIOLOGY/ECOLOGY
General: It requires well-oxygenated waters and prefers fine, clean sand, clay, and coarse sand substrates. Maximum densities can range from 10,000 to 20,000 per square metre. Average lifespan is 2 to 4 years. Movement and dispersal: Hermaphrodite capable of self-fertilisation. Larvae are released into the water column. Spawning requires water temperatures >16 C and this is the minimum temperature for the clams to release their larvae. A single clam can release up to 400 juveniles a day and 70,000 per year. Larvae spawned late in spring and early summer can reach sexual maturity by the next autumn. C. fluminea spreads when it is attached to boats or carried in ballast water, used as bait, sold through the aquarium trade, and carried with water currents.

RISK STATUS
Environmental Impact: It may cause much damage to intake pipes used by power, water, and other industries that is very expensive to remedy. Many native clams are declining as C. fluminea outcompetes them for food and space. Invasion Stage (England): Since 2004 it has been discovered at three more sites on the tidal River Thames. Surveys indicate that the clam has now established dense populations at Ham, with evidence of annual recruitment. Given the substantial connectedness of the Thames to many of Britain‟s other rivers, it is likely that it will now continue to spread through Britain‟s waterways (Elliott & zu Ermgassen, 2008).

Introduction Pathways: Ballast water, hull fouling, live bait, aquarium trade.

Control: Where possible, heat treatment (>37 C) is effective. Mechanical measures, such as using screens and traps, can eliminate older clams and remove body tissue and shells from pipe systems. Chemicals, such as small concentrations of chlorine or bromine, are very effective for killing juveniles and sometimes adults.

RISK CATEGORY
B1 Medium/Isolated Populations

References Aguirre, W. and Poss, S. G. 1999. Non-Indigenous Species In the Gulf of Mexico Ecosystem: Corbicula fluminea (Muller, 1774). Gulf States Marine Fisheries Commission (GSMFC). Elliott, P. and zu Ermgassen, P.S.E. 2008. The Asian clam (Corbicula fluminea) in the River Thames, London, England Aquatic Invasions 3, 54-60.

Taken from Natural England Comissioned Report NECR0009
Horizon Scanning for new invasive non native animal species in England.
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