Cuyahoga River is historically one of the most polluted in the U.S.  It became famous as "the river that caught fire" in the 1960's which helped spur water pollution control activities that gave rise to the creation of the Environmental Protection Agency (EPA) and the Clean Water Act, among others.

More than four decades after the 1969 Cuyahoga River fire that sparked an environmental movement, efforts to clean up the crooked river appear to be a success based on the fish that are found there.

"Fish are our benchmark, our canary in the coal mine," said Cuyahoga River Restoration executive director Jane Goodman. "If the fish are abundant, healthy and diverse, then that is a good sign."

On Wednesday, a crew from the Northeast Ohio Regional Sewer District found such sign with the discovery of a three-inch walleye fingerling during a water-monitoring survey that involved collecting fish.

Although there are millions of walleye that live in Lake Erie about 10 miles away with a billion dollar a year sport fishing industry, the game fish is not found in Cuyahoga.

The fact that the walleye was found 10 miles from the river's mouth had naturalists buzzing with excitement.

Kevin Kayle, from the Ohio Department of Natural Resources' Division of Wildlife, who has been evaluating the quality of water on Cuyahoga for the past four years was thrilled by the news.

He said that the fact the Cuyahoga could possibly provide spawning grounds for the tasty game fish is a cause for optimism.

Kayle's study of the river's water reveal an improving diversity of larval fish based on habitat quality and the availability of aquatic food that live in the mud.

Sewer district crews caught several species of fish during the survey. The fish collected include pollution-intolerant species that include the likes of the greenside darter, golden redhorse, and the walleye.

Water quality monitoring crews found grass carp during previous fish collecting trips but no grass carp was caught this time. The fish is among several invasive species collectively known as the Asian carp.

The species is feared for the damage it could possibly cause to game fish if this manages to escape into the Great Lakes.

All of the grass carp found in the Cuyahoga River were found to be incapable of reproduction. It is suspected that they have escaped from private ponds.