What are Invasive Species?

Any species that are not native to Lake Champlain and may be likely to cause ecological or environmental harm are considered ‘invasive species.’

Lake Champlain Zebra Mussels

People, animals and natural forces have been moving plants and animals, intentionally or accidentally, from one habitat to another throughout history. Sometimes, introduced species are not a threat to new habitats. If the newcomers have natural predators in their new home they don’t significantly upset the ecosystem. Invasive species, however, lack predators in their new habitat and have aggressive growth patterns. If the ecosystem can’t keep a newcomer’s population controlled. Without natural, ecological controls such as disease and predators, the balance of that ecosystem is tipped. The non-native species out-compete the native plants and wildlife causing the native species to suffer, decline or become extinct. This reduces Lake Champlain’s native bio-diversity. Once they’ve established themselves, these species can be nearly impossible to eliminate.

Some examples of Invasive Species:

• Zebra mussels that entered Lake Champlain around 1993, have proliferated and smothered the native mussels, choked water intake pipes, and sliced swimmers’ feet .
• Alewives– first found in the lake in 2003- have become a dominant forage fish. Recent winter kills of alewives have resulted in tons of rotting fish washing ashore after the ice has melted (see picture below). This die-off does seem to have affected the overall lake-wide population of that fish, however.

Alewife die-off in Lake Champlain

• Eurasian Milfoil has spread throughout Lake Champlain, affecting both swimmers and boaters. Its cousin Variable-leaved Milfoil was found in 2009 in Missisquoi Bay; it too can become a nuisance.

Lampreys on Lake Trout

• Sometimes native species can also get out of balance with the ecosystem. Sea Lampreys are believed to be a native species, but their populations are currently so high that they threaten the survival of other native species, like Lake Trout.

Where are they from?

More than 60 percent of the invasive species (that we know about) have entered by way of canals, especially the Champlain Canal at the southern end of the lake. Many other invasives are ready to join them. The Hudson River (which is connected to Lake Champlain by The Champlain Canal) hosts more than twice the number of exotic species as Lake Champlain; the Great Lakes host nearly four times as many.

Now let’s look at some of the current and up-coming threats to Lake Champlain’s current ecosystem.

Next: Invasive Fish Threats to Lake Champlain ( Next >> )