Just how dirty is the Ohio River?

CINCINNATI - All summer long, aquatic biologists with the Ohio River Valley Water Sanitation Commission patrol the river taking part in a process called electrofishing.

"The way electrofishing works is we apply electricity to the water to stun the fish, to put us in a position where we can remove them from the water and put them in a live well so we can examine them and then set them free," said Rob Tewes, an ORSANCO Aquatic Biologist.

Biologists place anodes into the water. A generator powered machine then produces low level shock waves into the water temporarily immobilizing the fish.

"It's minimally stressful on the animal and a lot less stressful than putting them in a net, and a lot less stressful than a putting a hook through their face."

The Ohio River is also a source of drinking water for more than five million people from Pennsylvania to Illinois. The testing by ORSANCO helps determine pollution and mercury levels in the river.

"People still think the river is very dirty and polluted, but when you have a fish population like we've got in this river I think it says something about our water quality," said Jeanne Ison, a spokesperson for ORSANCO.

On Wednesday, more than a dozen different species of fish were removed from the river. It's estimated there are more than a 120 species.

"So basically by sampling fish, which is a quick and easy method, we can get a quick assessment of our river," said Ryan Argo, an ORSANCO aquatic biologist.