(The Oregonian) Mount Vernon, population 524, isn’t described as ground zero too often. After crawfish from Ohio and Kentucky started showing up in a stretch of the nearby John Day River in 2005, however, researchers said the term fits.

Well-intentioned teachers released the invasive rusty crawfish at the end of science lessons, it seems, and it began to push out the signal crawfish, the only Oregon native species.

Perplexed wildlife officials put the classroom together with the invasion by process of elimination. It’s illegal in Oregon to fish with its invasive brethren as bait so none escape into the wild, and unlikely someone would import bait from 2,000 miles away. However, the rusty crawfish was a frequent visitor to science classrooms in the area.

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