Asian Clams (Corbicula fluminea) prefer sand or fine gravel substrates in lakes and rivers that contain high levels of oxygen. In Vermont, Asian clams are currently only found in Lake Bomoseen.
Asian clams are round and have symmetrical, triangular shells with distinct concentric rings that are easily felt with your fingernail. Shells range in color from greenish-yellow to dark brown and are white or light purple and smooth on the inside. Asian clams are small, typically less than 1.5 inches. Native clam species are flatter and have smooth, more asymmetrical shells.
Asian clams can reproduce and spread rapidly. It is capable of both sexual reproduction and self-fertilization, enabling it to produce thousands of larvae. Dense populations can have both ecological and economic impacts.
Asian clams were found in Vermont in 2016 so the full impact they may have on Lake Bomoseen is not yet known. In other invaded waterbodies around the country, Asian clams compete with native species for food and space. They can also clog the pipes of power plants, water treatment plants, and irrigation systems causing damage requiring costly repairs.
Control and Prevention
There has been limited success in containing Asian clam populations using benthic barriers, which are rubber or PVC mats installed on a lake bottom and weighted down with rebar. These barriers suffocate the clams by reducing dissolved oxygen levels. However, the best management option is spread prevention.
Asian clams can be spread unintentionally on boating and fishing equipment. Larvae are microscopic and easily transported in small amounts of water. Larvae suspended in the water column may also spread by water currents.
The most effective way to prevent the spread of Asian clams is to practice Clean, Drain, Dry spread prevention methods. Drain all water from your boat, canoe, kayak, and other vessels and equipment used in the water. Clean off any mud and plant fragments and dispose of properly. Dry all damp areas of boats and vessels, such as livewells and bilges, with a towel and let air dry in the sun for at least five days before using in another waterbody. If this is not possible, rinse equipment with hot, high-pressure water.
For more on spread prevention
VT Department of Environmental Conservation
For volunteer opportunities to help monitor and protect Vermont's waters
US Geological Survey Nonindigenous Aquatic Species
New York Invasive Species Information