Didymo: A New Kind of Invader

At the Council meeting last week in Missoula, Brian Marotz of Montana Fish, Wildlife & Parks described a recent phenomenon below Libby and Hungry Horse dams: the proliferation of a form of invasive algae called didymosphenia gemenata, also known as "rock snot" and didymo. Didymo was first reported in New Zealand in 2004 where it's become a significant problem. It's also been found in North and South America.

According to Marotz, the plant has the potential to cause great harm to habitat and fish by choking out the insects that fish feed on. Very little is known about why didymo is growing near the dams. It was first noticed below Libby Dam several years ago, and then below Hungry Horse about three years ago. Marotz noted that research is underway to better understand didymo's effect on habitat and how to address the problem.

"For some reason, it's proliferating," says Marotz. "It's alarming because now were starting to see a reduction in fish numbers as a result."