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Fishing worms can spread exotic harm to trees

Kelly McAlister from Johnston, Iowa, caught and released this 30-inch walleye while staying at Edgewood Resort on Long Lake. The fish succumbed to a nightcrawler, an exotic species unlawful to release on native soil, but a popular and legal bait for anglers statewide. (Jason Durham / For the Enterprise)

Last week I received an interesting call from a researcher working for the University of Minnesota.

They explained that they wanted to ask five questions about exotic species and their role in fishing tournaments.

I agreed since the transport and spreading of invasive species is a big deal. I assumed we'd talk about weeds, zebra mussels, snails and other aquatic hitchhikers.

Surprisingly, none of those plants or creatures was mentioned. They instead wanted to chat specifically about the exotic species...worms. That's right, worms. Not a rare new subclass or mutation that gives ordinary worms super-powers, just your average, find 'em in the backyard worms.

"What percentage of tournament participants dump their leftover worms at the public access once the tournament concludes," asked the researcher.

I replied that none of the anglers do. Minnows are different, since you can't legally transport lake-water to keep them alive, so the minnows are disposed of. But worms, specifically nightcrawlers, the unused bait is simply left in its container, thrown back in the cooler and kept until the next fishing trip.

I'm not sure I've ever seen someone dump out perfectly good worms. It would be comparable to throwing your crankbaits out on the pavement if you didn't happen to get a bite on them that particular day.

However, contrary to the beliefs of many, earthworms are not native to Minnesota soil. According to the Minnesota Department of Natural Resources website (www.dnr.state., most worms most likely would not have survived the glacial period that etched many of our lakes into the local terrain. According to the DNR and the University of Minnesota research team, the exotic worms were probably introduced via ships that arrived from Europe or Asia, which used soil or rocks as ballast, then dumped the contents on shorelines. European plants imported in the late 1800s or early 1900s also may have contributed to the exotic worm population.

You're probably asking yourself, "What's the big deal about worms?"

Unfortunately the exotic worms eat the "duff," the decomposing leaves on the surface of the forest floor that prevents erosion and is a catalyst for the development of hardwood trees. The degradation of this organic layer of protection can have an adversarial effect on Minnesota's native trees.

There is no economically feasible way to eliminate earthworms from our lands and forests, but preventing the introduction of exotic worm species to the environment is in the best interest of our native trees.

Worms themselves travel very little, which according to the DNR and University of Minnesota is typically less than a half mile over the course of 100 years.

Most worms you buy in bait shops are actually non-native worms, including the nightcrawlers, Canadian-crawlers and angle worms.

Though worms such as nightcrawlers are legal to use as bait, their distribution into Minnesota soil is actually illegal. In other words, if you are contemplating releasing a container of worms into your yard or simply discarding them at the access, it's a violation of Minnesota Statutes 84D.06.