Asian+Clam+-+2

=Asian Clam (Corbicula fluminea)=

General Information:
A small freshwater bivalve mollusk. Adults grow rarely larger than 40 mm and are commonly the size of a nickel. It has two thick hinged shells which are either yellowish-gold or light brown. 1

Detailed Description:
This species of clam is hermaphroditic, meaning that an individual produces both eggs and sperm, and is capapble of self-fertilization. While self-fertilization occurs, they will also release sperm into the water that can be captured by other clams for fertilization of eggs. The spawning season occurs for about six months, starting in the early summer. 2. They can release over 320-387 offspring daily depending on the conditions.

Habitat and Distribution:
The Asian Clam is a very hardy and persistent species that has become established across the United States above 40 degrees latitude. They prefer quiet waters with low salinity and sandy substrates, however, populations have been found thriving in water bodies with silty sediments. They also prefer to colonize in sunlit warmer areas near the shore, and typically avoid the low oxygen levels and cooler conditions associated with the deeper layers of the body of water. Although they are able to withstand freezing conditions, their ability to reproduce decreases with exposure to lower temperatures. They are native to Southeast Asia and were first reported on the west coast in the 1930's. They have spread to over 39 states and three water bodies in Massachusetts. 3.

Impacts:
The Asian Clam is known as the biofouler of power plants and industrial water systems.They can also alter the underlying layer of the body of water they have inhabited and can compete with native clams for space and food. In addition, they seem to be able to tolerate polluted enviroments better than the natives. 4. Nuclear service water (fire protection) systems are most vulnerable. In 1980, Asian clams clogged the service water system of a nuclear power plant in Arkansas, jeopardizing all fire protection plans. 1.

History:
The Asian Clam originated in Southeast Asia, and were first introduced by humans in 1924. By the 1970s, the clam occupied most of the Mississippi Basin, the Gulf Coast, and Eastern United States. It was discovered in Delaware in 1972, in New Jersey ten years later, and on Long Island in New York in 1984. Although New England was considered environmentally inhospitable, Asian clams were discovered in the lower Connecticut River, near Haddam Neck, Connecticut in 1990. Humans are responsible for the dispersal of this clam. There have been inadvertent releases by researchers. They were used as live bait and whole clams sometimes survived. Aquaria are sometimes released into lakes and rivers, which contributes to the spread of the clams. 1

Control Measures:
There are several ways the Asian clam can be controlled to minimize its impact on a power plant, water supplier, or industry. //Thermal regulation//, heating the water in the pipes to temperatures exceeding 37 degrees, is one method but not possible in most existing waters.

Mechanical regulation, using screens and traps to prevent mature clams from entering the water system and to remove clam bodies and shells from the system, is effective for dealing with older clams.

Chemical regulation, using small concentrations of chlorine or bromine to kill the juveniles, and in some cases, adults, is also very effective. However, state and federal environmental regulatory agencies are becoming increasingly restrictive as to the amount of chemicals such as chlorine that can be discharged from a facility. The current trend is to search for more environmentally-sound, yet cost-effective and efficient treatment methods, and thus move away from the use of chemicals altogether. 1.

Works Cited:
1.http://www.sgnis.org/publicat/nespp_4.htm 2.www.in.gov/dnr/files/Asiatic_Clam 3.http://www.mass.gov/dcr/waterSupply/lakepond/factsheet/Asian%20Clam.pdf 4.http://www.iisgcp.org/edk-12/EXOTICSP/Asianclam.htm