What animal lives in fresh water, doesn’t have feet or fins, but still finds a way to travel between lakes and then change its watery home?
The answer — Asian clams. Asian clams were found for the first time in Lake Pend in Oreille, Idaho last April. The people of Idaho would have been happier if they hadn’t arrived. When the clams were allowed to grow and multiply in Lake Tahoe, California, they caused extensive and costly damages.
So what’s the problem with this clam living in a lake?
This freshwater species is non-native, meaning that it came from a different part of the world. It is also invasive, meaning that it can transform the native ecosystems found here. Asian clams can affect water chemistry, nutrient dynamics, the flow of energy and the food web structure — all of which would drastically alter Lake Windermere as we know it if they get into our lake.
Asian clams, known scientifically as Corbicula fluminea, may be small, but when allowed to grow in large numbers can cause big damages. In Lake Tahoe, California, the clams live in dense colonies of 10,000 clams per square metre. Damages are caused by the means in which they eat, excrete and build their homes.
Eating: Asian clams are filter-feeders. Each clam can process five gallons of water a day. This filtering action moves nutrients through the water. They also feed off the bottom of lakes, re-mobilizing nutrients that may be buried in the sediments. When nutrients are present in water in unnatural levels they can cause unsightly algae blooms.
Excreting: The Asian clams excrete a substance that fosters the growth of benthic bacteria (slime-like layer), algae, and submerged plants.
Shell-building: Calcium sequestered from the water column into the clam’s shell is later deposited on the lake bottom and can serve as attachment surfaces for other invasive muscles and clams.
If the Asian clams proliferate, these changes in the aquatic ecosystem have the potential to affect key fishery resources, notably Kokanee salmon, and foster growth of algae and vegetation.
How might they get into Lake Windermere?
Unlike native clams and muscles that are transported in their larval phase by fish, larvae of the Asian clam are mobile and can attach to hard surfaces. Boat hulls and trailers are the most common means of transmitting this and other invasive species. Since some people take their boats between lakes, they can unknowingly be transporting Asian clams. Lake Pend Oreille is just a four-hour drive away from Lake Windermere, so the danger of them getting here is real.
What can I do?
The Invasive Species Council of BC’s approved method for preventing the spread of invasive species is to clean, drain and dry any equipment you use in one lake before transporting it to another. Cleaning means removing all plants and mud, then thoroughly washing everything. To properly drain your boat, drain wells, ballast and engine-cooling water. Finally, allow time for your boat to completely dry before launching into other waters.
You can make a lasting difference in your community and help prevent the introduction and spread of invasive species in B.C.
The Lake Windermere Ambassadors are a B.C. society representing a cross section of community stakeholders including local businesses, governments, seasonal and year-round homeowners, First Nations, youth and non-government organizations who share the vision of a healthy Lake Windermere.