LARIMORE, N.D.-Zebra mussels have gained a foothold in the Red River in recent years, but a group of Larimore High School students under the guidance of science instructor Lorie Berthold is exploring a possible way of keeping the invasive mollusks in check.

Larimore is a participating school in the Red River Basin River Watch program, and the students are raising crayfish to release into the Turtle River next spring. Crayfish are natural predators of zebra mussels, the students learned, and while the Turtle River doesn't have a documented zebra mussel infestation, the Larimore students are working to ensure the invasive species doesn't find its way into the Red River tributary.

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Larval-stage zebra mussels, called veligers, first were discovered in the Red River near Wahpeton-Breckenridge in the summer of 2010, and zebra mussels now can be found all the way to Lake Winnipeg.

"When we first thought of this, we knew that we weren't going to solve the problem of zebra mussels itself, so we're sticking to the problem of overpopulation," said Ty Stromberg, a Larimore sophomore and member of the River Watch team. "So, we want to control it as much as possible."

A program of the Fargo-based International Water Institute, River Watch is a river ecology initiative aimed at getting students involved in watershed monitoring and education through hands-on learning experiences. A total of 26 schools from Minnesota and North Dakota and 22 schools from Manitoba participate in River Watch.

A highlight of the program is an annual River Watch Forum held every winter, in which participating schools submit presentations on their work as part of a competition among all of the schools.

The 2019 River Watch Forum is Feb. 27 at the Alerus Center in Grand Forks.

Tackling a problem

This year, participating schools were challenged with finding an issue or problem in their watershed and proposing a solution. Given the recent publicity about zebra mussels in the Red River and the damage they cause to the ecosystem by outcompeting native mussels and interrupting the bottom of the food chain, the problem seemed like a natural, Larimore students said.

"We just decided we're going to grow and breed crayfish and we're going to release them into the Turtle River-just to hope that they eat up some of the zebra mussels that are causing harm to the river systems," said Luke Tupa, a Larimore senior and River Watch captain along with Tucker Salander.

As River Watch adviser, Berthold admits it wouldn't have been her first choice.

"I tried to steer them in a different direction," she said. "There's a drainage problem with water running into the Turtle River. In theory, you can fix that problem, but they wanted this, and I said, 'OK, if this is what you want to do.' "

In researching zebra mussels and how to control them, the students learned that one crayfish can eat up to about 100 zebra mussels a day. Crayfish also lay up to 250 eggs, which they carry on their abdomen, and about 70 survive.

"There are some fish species and bird species that eat (zebra mussels), but we wanted to mainly focus on crayfish because they would be easier to catch," said Rylie Cronin, a Larimore sophomore River Watch member.

Trial and error

Initially, the students in mid-October tried catching crayfish at Larimore Dam and in the Turtle River, but a snowstorm the previous week sent water temperatures plummeting, and the students came up empty.

So, Berthold ordered three crayfish from a school supply company-one has grown and shed its exoskeleton, she says-and plans are in the works to purchase baby crayfish in December.

Two 55-gallon aquariums in Berthold's classroom house the crayfish, and any young crayfish that hatch will be transferred to a smaller aquarium.

Crayfish don't get along with each other very well, so no more than four adults can be kept in the same tank. The eggs hatch in seven to nine weeks, and the adults will eat the young crayfish if they get the chance, Berthold says.

"We looked this up because I didn't know a lot of things about crayfish," she said. "I knew they only lived three to five years (in the wild), but in captivity, they can live almost 20 years."

As part of the River Watch Team Challenge assignment, each participating school must put together a "story map" presentation using ArcGIS, a platform for managing and sharing the information they compile. In the case of Larimore's project, the presentation will include background info and highlights on their research. There'll be a map of the watershed showing crayfish release sites, photos of the project and perhaps some fun facts about crayfish.

The students also were required to make a presentation about their project, and team members on Wednesday were scheduled to present their research to the Grand Forks County Water Board.

From trying to catch crayfish in ice-cold water to raising them in captivity, there are plenty of unknowns. That's where the learning-and the fun-come into play. If history is any indication, the Larimore students will do well in February's River Watch Forum. Under Berthold's direction, Larimore placed first in 2015, 2016 and 2017 and third in 2018.

The Minto (N.D.) River Watch team took top honors in 2018 for their project and presentation on community engagement and stewardship activities in the Forest River Watershed.

Larimore was the first North Dakota school to participate in River Watch, which launched in 1995 with four schools and continues to grow, Berthold said.

"There's a little work to it, but it's fun to meet other people that are interested in the same things you're interested in-that's what I like," she said. "River Watch is getting bigger and bigger. Most of these kids are in sports and other activities, too, so it takes a lot of time."