Tasty Invaders

Students and professors find crayfish study to be rewarding — and delicious.

Research Cajun style: scientists and students turned an invasive species from Sparkling Lake into a tasty rusty crayfish boil. Photo: Gretchen Hansen

Doing important research in the upper reaches of Wisconsin can really build up a person’s appetite. Luckily for the UW–Madison students who were studying ways to eradicate the rusty crayfish from Wisconsin lakes, they could eat their findings.

An invasive species introduced into Wisconsin lakes and streams around 1960, rusty crayfish wreak havoc on entire ecosystems due to their aggressive nature and opportunistic feeding habits — essentially clear-cutting all aquatic plants in their path.

Being opportunistic feeders in their own right, the undergraduate and graduate students working on this study since 2001 at the Trout Lake Research Station in Boulder Junction, Wisconsin, quickly realized they were catching a main ingredient in many Cajun meals.

“In the early years, we were pulling out hundreds of crayfish every day,” says Gretchen Hansen ’03, PhDx’12, a UW zoology graduate student. “It was like, what do we do with these things? We know they taste good … so maybe we should eat them.

“Our favorite recipe was crayfish étouffée,” she says. “We ate that one a lot.”

There was plenty to eat, too, since roughly 90,000 rusty crayfish were caught during the intensive trapping program at Sparkling Lake. With thirty to forty students, teachers, and advisers staying at the research station during the summers, those dinners were one of the many ways people could unwind, bond, and have fun socializing.

“I describe it as summer camp for college kids,” says Hansen.

But the project meant more than meals and good times. It was also highly successful at reducing the rusty crayfish population. In 2001, the average trap caught twenty-five of the crustaceans each day. Now, it takes ten traps, on average, to catch a single invader in a day.

“The native species are increasing in the lake,” says Stephen Carpenter MS’76, PhD’79, a UW professor of zoology. “So, if you’re a rusty crayfish, your babies are very likely to be eaten by a native predatory fish.”

The experiment has been important, says Carpenter, because, “if it succeeds, it will show that this obnoxious invader can be eliminated.”

And while that’s great news for ecosystems throughout the region, it’s bittersweet for those who still work on the project and are craving Cajun.

“We only have a crayfish boil now maybe once a summer,” says Hansen.

Editor’s Note: For those who want to engage in an invasive-species culinary adventure, we include the recipe below.

Rusty Crayfish Étouffée

Ingredients

• 1 stick butter

• 2 cups chopped onions

• 1 cup chopped celery

• 1/2 cup chopped green bell peppers

• 1 pound peeled crawfish tails

• 2 teaspoons minced garlic

• 2 bay leaves

• 1 tablespoon flour

• 1 cup water

• 1 teaspoon salt

• Pinch of cayenne

• 2 tablespoons finely chopped parsley

• 3 tablespoons chopped green onions

Directions

In a large pan over medium high heat, melt the butter. Add the onions, celery, and bell peppers and sauté until the vegetables are wilted, about 10 to 12 minutes. Add the crawfish, garlic, and bay leaves and reduce the heat to medium. Cook the crawfish for 10 to 12 minutes, stirring occasionally. Dissolve the flour in the water. Add the crawfish mixture. Season with salt and cayenne. Stir until the mixture thickens, about 4 minutes. Stir in the parsley and green onions and continue cooking for 2 minutes. Serve over steamed rice.

Published in the Spring 2011 issue