Invasive Golden Clam Discovered in Lake Champlain by LCC Volunteer

On a sunny late-October day, a dual-sided rake head tied to a twenty-five-foot length of rope sailed through the air and broke the previously still water of a boat launch in Whitehall, New York with a splash. Ashley Leemans, a volunteer with the Lake Champlain Committee (LCC), reeled in the rope, and picked through the pounds of submersed plants that collected on the tines to identify what species are present. It’s a part of routine monitoring for volunteers in LCC’s Champlain Aquatic invasive Monitoring Program—CHAMP—where participants are trained to survey for invasive species, both those that have been detected in Lake Champlain and those that have been found in nearby waterbodies on the “watchlist”. While sifting through her first rake toss of the day, Ashley found something alarming. 

Ashley photographed what she suspected to be one of the species on the watchlist—golden clam (Corbicula fluminea)—and sent details to LCC. We followed up with program partners and state agencies to confirm her finding of the first known golden clam in Lake Champlain. The aggressive aquatic invasive species (AIS) has been documented in the region since 2008 but has not been seen in Lake Champlain until now. It’s native to the eastern Mediterranean, Asia, Africa, and Australia. Golden clam is hermaphroditic, meaning a single individual can start a new population. The species is known to reproduce quickly in other North American waterbodies. 

What’s next? 
The Lake Champlain Rapid Response Task Force—a collaborative of New York, Vermont, Quebec and federal agencies that LCC helped establish—met in November to review next steps to respond to the discovery. State and federal agencies are assessing the significance of this introduction and conducting additional surveys to determine the extent and outline follow-up actions.  

While the clam is invasive throughout North America, for it to be officially deemed the 52nd invasive species in Lake Chaplain an adverse impact on native ecology, the ecology, or human health needs to be proven. Non-native species refer to species not indigenous to a given area, while invasive species are non-native species that have a proven harm to the environment, the economy, and/or human health. As of now, only two clams were detected at this site, making it a non-native but not necessarily invasive in Lake Champlain. 

This discovery by an LCC CHAMP volunteer underscores the importance of ongoing efforts to protect the lake’s ecosystem and native species through early detection of invasive species and the value of community science programming like CHAMP. 

What do Corbicula fluminea look like? 
Golden clams have a triangular hinged shell and are usually smaller than a penny but can reach sizes of up to five centimeters in diameter. The exterior of their shells range in color from greenish yellow to dark brown and are marked with concentric growth bands that form distinct ridges you can feel. If you run your fingernail along a shell, you’ll feel coarse ridges and hear a washboard percussion instrument-like sound. The interior is white, bluish, or light purple and smooth. 

What’s the big deal with golden clams? 
Corbicula fluminea are aquatic mollusks first discovered in North America in 1938 in the Columbia River in Washington state. They have since spread across the contiguous United States and are now found in nearly all 50 states. Golden clams are aquatic invasive species in North America, which means that not only are they not native to our region, but they also actively harm the environment, the economy, and/or human health. A single adult can produce approximately 35,000 larvae per year, making eradication difficult once they become established. Large infestations can have numerous negative effects on ecosystems including out-competing native mussels, altering the nutrient cycle, disrupting habitat, and limiting planktonic food availability. Golden clams are filter feeders and excrete elevated levels of nitrogen and phosphorus in the lake-sediment interface, depleting oxygen, and triggering cyanobacteria blooms. Additionally, they can “biofoul” human-made structures such as water systems, costing an estimated $1 billion per year in the United States. 

Where are golden clams in the Lake Champlain Watershed? 
Unlike zebra mussels, which attach to hard surfaces, golden clams prefer open, sandy bottom areas with limited plant growth, where they can form dense, thick mats. In 2007, golden clams were documented in Lock 8 of the Champlain Canal, only two locks away from the Lake Champlain side of the canal system. In 2009, they were confirmed downstream of Lake Champlain in Becancour, Quebec in the St. Lawrence River. In 2010, they were detected in Lake George, New York. In 2016, the invasive clams were found in Lake Bomoseen, Vermont, and now inhabit a portion of the lower lake. Lake George drains into Lake Champlain along the La Chute River in New York. Lake Bomoseen drains into Lake Champlain via the Castleton and Poultney Rivers in Vermont. Lake Champlain is surrounded and that’s why state and provincial surveillance and the surveys conducted by LCC CHAMP community science volunteers are important.  

Managing golden clams: a case study in Lake George 

Significant effort was made to control the infestation of golden clams in Lake George with benthic matting. According to New York State’s Lake George Park Association, dozens of acres of the lake had rubber or PVC mats installed on the lake bottom and weighted down with rebar between 2010 and 2016. With 96%-100% golden clam mortality rates under the mats the method seemed promising. However, golden clams are tricky: they are hermaphroditic and a single individual can reproduce thousands of offspring in a single season—while mortality rates for the offspring are high, this high fecundity rate makes them quick to adapt and hard to eradicate so 96 to 99% mortality leaves enough golden clams to repopulate a site quickly. Benthic matting and the associated studies cost nearly two million dollars. The management strategy has since been abandoned and replaced with regular monitoring and spread prevention. Golden clams currently occupy 85% of sandy areas in Lake George, but the good news is they have not (yet) been found to be a nuisance anywhere in the lake.  

Shout out to Ashley and LCC CHAMP volunteers! 
We’re grateful to LCC CHAMP volunteer Ashley Leemans of Washington County Soil & Water Conservation District for acting swiftly and reporting right away when she found what she thought was golden clam while surveying in Lake Champlain’s South Lake. Big thanks to all our 2024 CHAMP volunteers. With 587 miles of shoreline there’s still plenty of need for more Lake Champlain CHAMP monitors. We prioritize the South Lake and northern reaches because of their proximity to other waterways with more populations of AIS and public access locations as they’re the most likely areas for new infestations given boating traffic but we welcome any new sites for 2025 monitoring.  
 

How you can help 

• Follow clean, drain, dry practices whenever you recreate on and around waterways--clean off any mud, plants, and animals from the boat, trailer, motor and other equipment. Drain all water from the boat, boat engine, and other equipment away from the waterbody. Dry anything that   encounters the water. 

• If you have access to a public or private Lake Champlain shoreline location and a few hours to spare each month from June through late October, consider becoming one of LCC’s community science volunteers for our Champlain Aquatic invasive Monitoring Program – CHAMP. We’ll train you how to identify AIS including critical “watchlist” species, supply you with any equipment you need for successful surveying, teach you how to throw an aquatic rake (it’s fun!), and support you throughout the season. 

• For folks interested in getting actively involved with spread prevention but who can’t make the time commitment of a CHAMP volunteer, we host annual beachcombing events and AIS harvesting programs. Fill out our volunteer response form and check the box for AIS monitoring and harvesting and we’ll be in touch when we schedule 2025 outings and events. LCC’s Champlain Aquatic invasive Monitoring Program is funded by LCC donors and the Lake Champlain Basin Program/NEIWPCC. Consider supporting us by becoming a member: lakechamplaincommittee.org/support.