Last year (2024), we shared news of a small infestation of elodea, a highly invasive aquatic plant, discovered in Crescent Lake on the Kenai Peninsula. Since then, a multi-agency treatment effort, led by the U.S. Forest Service (USFS), has been underway in hopes of eradicating the plant. One year in, we’re starting to see promising results.
Why this matters
You may be asking yourself: Who cares about some weeds in a remote lake?
Well, elodea can cause large-scale ecological disruption—and fast. It grows rapidly and can form a dense monoculture that disrupts native vegetation, fish, and recreation on the lake by making it difficult for anglers to fish and float planes to taxi.
It’s not just Crescent Lake we’re concerned about though. Despite its remote location, the lake sees significant recreational use and floatplane traffic. Elodea can establish new populations from even the smallest fragments that hitchhike on aircraft, watercraft, and personal gear.
Crescent Lake is a part of the Kenai River watershed and connects to the Kenai River— which is the source of upper Cook Inlet’s most productive salmon fishery and the most heavily-fished river in Alaska. So, what happens here matters downstream.
Every year, millions of salmon use the lakes and tributaries within the watershed to spawn and rear as juveniles. If established, elodea can choke out native vegetation and degrade fish habitat in these areas. This causes problems for salmon at multiple points in their lifecycle and can also displace resident species of fish making them subject to predation.
So, it’s best to contain the plant as quickly as possible when a new population is discovered.
Ongoing efforts
This year, 2025, was the first year in a three-year plan to treat four known patches of elodea in Crescent Lake. Over the summer, multiple agencies applied herbicides in three rounds with the final application taking place in August. Two different types of herbicides were delivered from a boat and a drip station. After treatments, personnel collected water samples and sent them to a lab for analysis to ensure the concentration of herbicide reached high enough levels to damage elodea.
Signs of promise
After one year of targeted treatments in 2025, we’re seeing early signs that the approach is working.
In 2024, we surveyed Crescent Creek and found a few rooted populations of elodea and a significant amount of elodea fragments on branches, downed trees, and rocks up to a mile downstream of the lake.
This year we went back after the first round of herbicide treatments and the rooted populations were still there but showed discoloration and were clearly beginning to die. We also didn’t find a single fragment of elodea in Crescent Creek—a major improvement from the pre-treatment survey. This is an encouraging sign about the efficacy of the herbicide treatments thus far and is promising news for the rest of the Kenai River watershed.
What’s ahead
The 2025 season laid a strong groundwork for elodea eradication in Crescent Lake, but it’s just the beginning.
The treatments will continue into 2026 and 2027 and will be crucial to the health of Crescent Lake and the surrounding waters. Surveys of the lake will continue to be completed to determine if the distribution of elodea has changed and monitor the impacts of the treatment. Water samples will be collected to measure herbicide concentrations and change the prescription for future years as needed.
Doing your part
You don’t have to be a biologist or certified applicator to help in the fight against invasive species like elodea. In fact, the public plays a critical role in protecting our lakes and rivers.
You can educate yourself by knowing what the plant looks like. If you’re unsure, snapping a photo and reporting it can be extremely helpful. Alaska is a large state with a lot of waterbodies, so there’s a good chance that the vegetation you’re seeing hasn’t been surveyed before and a picture can go a long way.
Clean. Drain. Dry. Every time.
You’ve probably seen this before and it is truly one of the most effective and easy things we all can do to stop the spread of not just elodea, but other invasives as well. Clean your boat, kayak, fishing tackle, and hiking gear. Drain all the water from your motor and bilge. Dry everything as much as possible before going to a new waterbody. If you’re a pilot, inspect your floats and personal gear when moving between lakes. Even a tiny fragment can start a new infestation.
We’re beginning to see positive results at Crescent Lake, but it’s just the beginning. Long-term success is going to take not only continued treatments, but community support as well. So next time you head out, remember—each of us has a role to play in sustaining our salmon, and the waters we all depend on.
