Large mayfly swarm sign of good water quality, biologist says

PARKERSBURG, W.Va. (WTAP) - Along with fireworks this Fourth of July, there were a lot of mayflies.

The mayflies came out in the area as a part of their mating season.

They were all over Parkersburg hovering around lights and swarming everywhere.

Experts say that despite the alarm from many who were out on the holiday night, this is actually a sign of the water quality in the river being good.

“The good news is that it’s a sign of clean water. And so, seeing them there that’s a sign that the river is in relatively good shape. Probably has plenty of oxygen in it. And maybe the silt loads are down a little bit because they can tolerate some silt but they need a lot of oxygen. And it’s a good sign if they’re out there,” says Marietta College biology professor, Dave McShaffrey.

McShaffrey says that the mayflies are harmless and there is no need to spray them with pesticides because they die off roughly 48 hours after mating season.

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