With summer in full swing and winter knocking on our door, elodea surveys are underway across the state.
Elodea is Alaska’s first aquatic invasive plant and it can wreak havoc on any ecosystem it establishes itself in. Eradication of elodea can be quite expensive. And it can spread from small fragments so if it’s not entirely eliminated from infested systems odds are good that it will bounce back. Elodea tends to outcompete native vegetation and it grows so thick that it can displace native fish species like salmon. Overall elodea is not something you’d want in your lake.
Unwelcome intruder
Resource managers recognize the threat elodea poses to our native flora and fauna. There are multiple groups and organizations such as the Alaska Invasive Species Partnership, Kenai Peninsula Cooperative Invasive Species Management Area, and the Mat-Su Elodea Taskforce that bring partners together to work towards the goal of stopping the spread of invasive species.
Current invasions loom as potential source populations for elodea to spread throughout the state. Early detection surveys and public reports of suspected invasive species are key ways that new infestations are discovered.
A new infestation
In September 2023, a Chugach National Forest (CNF) field crew discovered a new infestation while conducting an elodea survey at Crescent Lake located near Moose Pass within the Chugach National Forest. With that discovery the Kenai Peninsula is no longer free from elodea infestations.
CNF biologists convened a working group with partners to aid in the eradication of this newfound population. In 2024, the working group gathered data about Crescent Lake and the Creek system to inform treatment options and the herbicide prescription, underwent the state and federal permitting process, and sought funding for the full three-year herbicide treatment. Treatment is expected to start in the summer of 2025.
Survey methods
There are a lot of different ways to conduct elodea surveys: two people in one boat, snorkel surveys, or individuals in their own boats. Staff here at Cook Inlet Aquaculture Association (CIAA) have conducted surveys with two people in a motorized boat and with two people in separate pack rafts.
When you have two people in one boat, one person drives to each survey point along the shoreline and the other throws the vegetation rake at each site. The two work as a team during the surveys. In between the predetermined sampling points both crew members will be visually inspecting the shoreline for elodea.
They have the option to complete as many additional rake throws as they want, so if there is ever any question about the vegetation seen they can toss the rake and get it up close to identify it with the use of a guide.
You're going to need another raft
Surveying with two people in their own separate pack rafts allows for two elodea surveys on the same waterbody at the same time. This is accomplished by both people inflating their pack rafts and heading in opposite directions around the lake. It could actually be done with any number of surveyors, maybe splitting the lake into different sections for observations.
They each have the same predetermined sites loaded into a GPS where they will stop to throw the vegetation rake. In between sites they visually inspect the shoreline, and similar to the last method they can throw the rake as much as they deem necessary to feel confident in identification. This method allows for a higher likelihood of identifying elodea if it is present in the waterbody.
At the end of any survey it’s important to ensure that all gear is cleaned and all plant fragments removed. The best thing to do is clean, drain, and dry all equipment before moving it to another waterbody. Cleaning equipment with a 10% bleach solution is essential if you are unable to dry equipment in between waterbodies, to ensure that nothing can be spread between lake systems on your sampling gear.
Which method is best?
Different factors determine the type of survey. Is the lake on the road system or is it remote, requiring a flight or hike in? What type of boat is available for the survey? What is the crew’s level of experience? What is the size of the lake? And how many people are available to help?
Pack rafts are smaller and easy to transport to lakes that are remote and require a hike or a flight to get to them. It’s relatively easy to trailer motorized boats to road system lakes that have boat launches, but that doesn’t mean a pack raft survey can’t be conducted on those lakes too.
Crews on larger lakes with limited time may be able to cover more ground working together in a single boat versus both in pack rafts. When training new crew members it makes sense to conduct the elodea survey together so they become familiar with the process before heading off on their own for a survey.
After the surveys
During any type of elodea survey it’s important to record your findings and report them to the Alaska Exotic Plants Information Clearinghouse. This clearinghouse stores all reported survey results for the state. It’s important to send survey results in so everyone can remain up to date on current survey efforts. It also serves as a central location where anyone can go to look up invasive species information and any current, known infestations.
If at any time during the survey, elodea or another invasive species is found the survey should switch to determining the extent of the infestation and mapping it as well as you can to report it to the Alaska Department of Fish & Game.
