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New aquatic invader enters Adirondack waters

September 7, 2010
Adirondack Daily Enterprise

The right person at the right place led to the detection of a new aquatic invader in Lake George. While recreating in a bay near Lake George Village with his family, a scientist with the Darrin Fresh Water Institute in Bolton Landing noticed something in the water that he had never seen before - it turned out to be Asian clam.

The Asian clam (Corbicula fluminea) is widespread across the country, but its range in the Northeast has been limited to the southern New England states, central New York and Long Island. Its detection in Lake George is the first in the Adirondack region, pushing the boundary of the clam's range north.

Soon after the initial discovery, groups in the Lake George area organized a response. Scientific divers donned their scuba gear and explored the southern end of the lake for the extent of these unwanted underwater inhabitants. Preliminary surveys revealed that the population remains concentrated to several acres in one general location. This may yield a unique opportunity to eradicate the infestation, which could involve laying benthic matting on the lake bottom to cut off the oxygen supply and smother the introduced species. This technique is also used to control zebra mussels and invasive aquatic plants.

Article Photos

(Photo — Emily DeBolt, Lake George Association)

Native freshwater mollusks, which include snails and mussels, are an important part of an aquatic ecosystem. They filter water, cycle nutrients and provide a food source for fish, invertebrates, waterfowl and wildlife such as river otters and muskrats.

The Asian clam, however, is not native here and may cause serious problems. Elsewhere in the country, these clams reach population densities of 10,000 to 20,000 individuals per square meter. At these numbers, the clams are biofouling hazards, clogging water intake pipes, disrupting water flow and affecting power and water suppliers and other industries. They also eliminate habitat for native mollusks and create excess amounts of waste, leading to algae blooms and reduced oxygen levels.

Originating from Southeast Asia, the Asian clam made a quick trip across the country. First introduced to the west coast of North America in the 1920s, likely as a food item, it was detected in Washington state in the 1930s, throughout most of the Midwest in the 1970s, along the Eastern seaboard in the '80s and in southern New England in the '90s.

How is this clam moving around such a large area? Humans. Anglers use the clams as live bait, and whole clams sometimes survive. Juveniles are transported in water in bait buckets or boats. Dumping contents of aquaria into lakes or rivers also contributes to the spread of these clams. In the aquarium trade, Asian clams are known as "pygmy" or "gold" clams.

Adults are about the size of a nickel, rarely growing larger than 1.5 inches, and have two thick, hinged shells that are yellowish-gold or light brown with distinctive concentric ridges. The preferred habitat is shallow, warm water with sandy or gravelly substrates. Water temperatures in this region led some to believe that waters were environmentally inhospitable for this species to succeed, since water less than 2 degrees can kill the clam. But, the size of clams in Lake George indicates that they have successfully reproduced for at least two years.

Scientists will continue monitoring water quality and sediments in the coming weeks to determine suitable conditions for this species in our area. To find out more about efforts under way, contact the Darrin Fresh Water Institute at 518-644-3541.

Each new invasion reinforces the importance of preventing the transport of invasive species. Check, clean and dry all watercraft and equipment before moving between waterways. Never empty a fish tank into public waterways. Regularly surveying for new species and reporting them when found helps arm responders with the best chance for success.


Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at



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