Preventing Elodea Colonization of Salmon Habitat

Alaska has one of the most productive salmon fisheries in the world but an invasive plant threatens the quality of lakes for salmon spawning. Funds from the Bipartisan Infrastructure Law (BIL) have energized early detection efforts to find and prevent the spread of non-native Elodea to freshwater salmon habitat.

Salmon spawning in Tazimina Lake, Lake Clark National Park and Preserve.

NPS/DAN YOUNG

Elodea is the genus for a group of waterweed species that are highly invasive aquatic plants. It is easily spread between waterbodies and, once established, is very difficult to eradicate.

Elodea can spread to new waterbodies by small pieces of the plant attached to boots, boats, and float planes that have been in infested waters. Elodea is the first known freshwater invasive plant to be found in Alaska. Once a bed of Elodea becomes established, it grows rapidly, blocking light and taking up nutrients. The plants clog waterways and negatively impact fish, including salmon, by altering the physical structure of salmon habitat—salmon use rocky stream and lake bottoms to lay their eggs.

A recent study linked Elodea to negative impacts on salmon. Study authors found that widespread establishment of Elodea may alter salmon habitat in ways that affect fish growth and can lead to population-level impacts by inhibiting the return of salmon to their natal freshwaters for spawning.

Elodea grows thick in water bodies and changes the structure of fish habitat.

U.S. FISH AND WILDLIFE SERVICE

Although Elodea has not yet been detected in Alaska national parks, it is known to occur in waterways that are used to access parks. Most of these high-risk areas are only accessible by float planes or boats—the main ways Elodea spreads. “Early detection efforts need to be greatly expanded,” says Dr. Tobias Schwoerer, Assistant Research Professor of Natural Resource Economics at the University of Alaska Fairbanks. “Current risk assessments only cover approximately 700 of the more than 200,000 lakes used by floatplanes in Alaska.”

With Bipartisan Infrastructure Law funds, the National Park Service will survey high-risk rivers and lakes for invasive Elodea and treat nearby infested waterbodies to remove it.

Controlling the spread of invasive species is a serious challenge. Today, most of Alaska’s lands and waters have few or no invasive organisms. However, warming water and air temperatures are making freshwater and terrestrial habitats more vulnerable to invasions, putting Alaska’s self-sustaining wild native fish and wildlife populations at risk.

A recent analysis on the economic impacts of the continued spread of invasive Elodea on Alaska’s commercial sockeye salmon fisheries, not including subsistence and recreational impacts, estimated a total mean annual loss of $159 million per year. Enhanced interagency collaboration and coordination with Alaska Native Tribes and other local groups is needed to support resilient, sustainable fish and wildlife populations in Alaska.

About the Bipartisan Infrastructure Law

The Bipartisan Infrastructure Law makes critical investments in the resilience and restoration of America’s lands, skies, and waters, and enhances conservation and recreation opportunities. Visitors will see tangible results such as repaired and upgraded trails and campgrounds, removal of invasive species, as well as healthy wetlands, grasslands, and forests.