Nearly 20 years after the Cuyahoga River last caught fire, officials say Lake Erie and its tributaries are cleaner than they have been in decades.

Scores of Lake Erie beaches will be open in Ohio this year, and more than 25 million walleye thrive in Erie's waters. Boating has become so popular that many marinas in the Toledo area are running out of dock space.A few decades ago, Lake Erie had only three clean beaches, and fish were dying at a rapid rate. An oil slick on the Cuyahoga caught fire June 22, 1969.

The dramatic improvement has been caused primarily by a decrease in phosphates and other nutrients that caused algae to flourish in Lake Erie, using up oxygen and killing fish, said Laura Fay, a research associate for the Center for Lake Erie Area Research.

Phosphate pollution levels were decreased largely through improvement of sewage treatment plants, she said.

Half the people living in the Great Lakes basin live near Lake Erie, including residents of Cleveland, Toledo, Detroit and Erie, Pa. Eleven million people use Lake Erie for their drinking water, Fay said.

Although fish now appear to be thriving in the shallowest of the Great Lakes, Fay said the bottom of Lake Erie and its tributaries has sediments contaminated with such materials as mercury and PCBs.

Funding for research and cleanup on the Great Lakes has been decreasing, she said, even though contaminated sediments are a more chronic problem than phosphates.

"I hate to see people sit back and rest on their laurels," Fay said. "We've really come a long way, but the toxic problem is something we really can't see. Some of the effects are really going to be subtle. We might have lower reproductive efficiency of walleye or darter, but we're not going to see that for a while."