Invasive crayfish crisis: Scientists’ quest to protect native habitats

It is not a fair battle: Two scientists on a tiny boat against one of the world’s most invasive species.

For the past six years, Loyola University Chicago ecologist Reuben Keller and his students have been waging war against red swamp crayfish — a non-native threat to the environment.

Over the years, Keller’s team has set up 200 traps in the Chicago River, and twice a week in summer and fall, they clear them and restock them with a delicacy crayfish simply can’t resist: hot dogs.

“Hot dogs are really attractive to these crayfish,” Keller told Scripps News. “So that means that now we purchase and use vast numbers of hot dogs.”

During a recent river outing, Keller and his student Sydney Ware extracted 26 crayfish from the traps and anesthetized them with clove oil — a humane method to kill the creatures.

Red swamp crayfish outcompete other native species for food and habitat — and can cause structural damage to dams and levees.

“It doesn’t matter what is threatening them. Their response is to rear up or show their claws and they want to fight,” Keller said.

The professor says his team has substantially reduced the invasive species in the part of the Chicago River where they deployed the traps, which is good news for the native biodiversity and scientists battling red swamp crayfish worldwide.

“What we’re discovering here is equally applicable in the Chicago River as it is in other places all around the world where people are trying to catch these crayfish,” Keller said.

The creatures used to be kept as science pets in elementary schools and were sometimes sent home with students. That’s how Keller believes they were introduced to the Chicago River.

“I am sure that a lot of parents were horrified when their children turned up with ‘Here are the crayfish! We’re going to keep them as pets!’ And I’m sure that a lot of parents said, ‘Actually, no, we’re going to go and release them into a nice aquatic habitat.'”

The species comes from the Southeastern U.S. where it is a big part of the food culture. But Keller insists that no Chicagoan finding them in the river should eat them because of a nearby sewage treatment plant.

Keller says globalization is to blame for invasions and is urging countries and industries to try harder to safeguard native ecosystems, along with their environmental, recreational and economical benefits.

“The best thing that we can do to reduce future invasions, to reduce the impacts, is to stop moving these organisms around.”