Asian clams found in Shuswap Lake

Thursday, September 17, 2020

Dead Asian clam (Corbicula fluminea) shells found on the beaches of the Shuswap Lake last year prompted a survey of the near shore area now that water levels are low enough to access the potential habitat for this species. 

The survey found live populations of invasive Asian clams at two locations: Sunnybrae and Canoe Beach, and surveys are still underway.

“At Sunnybrae we were finding around 20 clams per square metre of lake bed”, said Sue Davies, Aquatic Coordinator for the Columbia Shuswap Invasive Species Society.

The survey was conducted by the Columbia Shuswap Invasive Species Society with funding from the Shuswap Watershed Council, direction from the Ministry of Environment and Climate Change Strategy, and assistance from the Invasive Species Council of BC Job Creation Program.  The Asian clam is not to be confused with invasive zebra and quagga mussels (ZQM), which are not currently known in BC. Ongoing prevention and monitoring for ZQM continues in the province, along with border inspection stations for watercraft entering British Columbia.

To avoid spreading aquatic invasive species, including Asian clams, to other lakes and rivers in B.C., it is important to clean, drain, dry all gear and watercraft following every use.

"The larvae of this species are microscopic," said Davies, "They could hitchhike in the smallest amount of water in your watercraft and survive to populate another lake.  Please make doubly sure that you clean, drain, and dry all gear and watercraft every time you leave a lake or river - even if you’re going to re-launch somewhere else in Shuswap Lake. This is an important measure for all watercraft: boats of all kinds, kayaks and canoes, paddleboards, and inflatables. Prevention is key."

Asian clams have been kept as aquarium species, used as bait, and eaten by people.  Any one of these uses may have resulted in dead shells or unwanted live animals being discarded into the lake and is another potential pathway for this species to have found its way into the Shuswap Lake. Never dump live animals or plants into the wild, including waterways.  It is illegal to introduce an aquatic species into a body of water where it is not native, unless authorized under federal, provincial or territorial law (Federal Aquatic Invasive Species Regulation). It is illegal to possess, breed, ship or release species listed under the Controlled Alien Species Regulation.   

This is the first confirmed presence of live Asian clams in the Shuswap. However, this is not the first confirmation of Asian clams in BC: they are known to exist in lakes in the Fraser Valley and on Vancouver Island, as well as in 38 US States and three of the Great Lakes (Erie, Michigan, and Superior). There are native mussels, such as the Oregon floater mussel and the Winged floater mussel, that can be confused with the Asian clam. The Asian clam shell is triangular shaped and usually less than 2.5 cm but up to 6.5 cm in length, and yellow-green to light brown in color with elevated growth rings.

Asian clams are small bivalve shellfish, originating in Asia. An individual can produce up to 70,000 eggs per year under optimal conditions and they can reach densities of up to 10,000-20,000 individuals per square metre of lake bed.  They are filter feeders that can reduce biodiversity and food available for fish. Dense populations may have the potential to clog filters on hydro systems and water pipes, imposing costly maintenance.  They are also known to harbour parasites that are harmful to humans if the clams are consumed raw. 

So what can be done?  Unfortunately, once established, eradication of Asian clams from a complex, connected waterbody is very unlikely and management methods are limited.  Impacts to the system are difficult to predict and depend on several factors. The best thing you can do is prevent further spread to other lakes or rivers.  Clean, Drain and Dry your gear and watercraft, and never release live animals or plants into waterways.

The Columbia Shuswap Invasive Species Society has also been monitoring the Shuswap for invasive Zebra and Quagga Mussels, a different invasive aquatic shellfish, and to-date, they have not been detected anywhere in BC waters.

Members of the public are asked to please report any suspected invasive species via the Provincial “Report Invasives BC” smartphone application (available for download from www.gov.bc.ca/invasive-species) and any suspected invasive zebra or quagga mussels to the Report All Poachers and Polluters hotline 1-877-952-7277.

A fact sheet for Asian clam is available at https://www2.gov.bc.ca/assets/gov/environment/plants-animals-and-ecosystems/invasive-species/alerts/asian_clam_alert.pdf

Travellers bringing watercraft to BC are encouraged to visit the provincial website, https://www2.gov.bc.ca/gov/content/invasive-mussels/bringing-your-boat-to-bc

The Columbia Shuswap Invasive Species Society is a non-profit organization dedicated to the prevention, management and reduction of invasive species in the Columbia Shuswap Regional District. CSISS is thankful for the generous support of the Habitat Conservation Trust Foundation, Shuswap Watershed Council, Columbia Basin Trust, the Columbia Shuswap Regional District, the Ministry of Forests, Lands and Natural Resource Operations and Rural Development, the Ministry of Environment and Climate Change Strategy, and the Ministry of Transportation and Infrastructure.

To learn more about invasive species in the Columbia Shuswap region please visit: http://www.columbiashuswapinvasives.org

View CSISS media release