Despite decades of efforts to restore and protect the Great Lakes, dozens of old power plants still are allowed to kill hundreds of millions of fish each year by sucking in massive amounts of water to cool their equipment.

Records obtained by the Tribune show that staggering numbers of fish die when pulled into the screens of water intake systems so powerful that most could fill an Olympic swimming pool in less than a minute. Billions more eggs, larvae and juvenile fish that are small enough to pass through the screens are cooked to death by intense heat and high pressure inside the coal, gas and nuclear plants.

Then the water is pumped back into Lake Michigan and the other Great Lakes up to 30 degrees hotter, encouraging the growth of oxygen-depleting algae that kills fish and fouls beaches.

Known as "once-through" cooling, the process is banned at new power plants. But for nearly four decades, federal and state environmental regulators largely have ignored the issue at old plants, even as fish populations decline sharply throughout the lakes and states spend millions of taxpayer dollars to stock the waters with game fish.

Cooling intakes kill fish prized by anglers and sold in supermarkets, along with many more smaller fish and other aquatic organisms that those species depend on for food. Critics compare the outdated technology to the Bass-o-Matic, the fish-pureeing prop from an old "Saturday Night Live" sketch.

"These plants are consistent killers, plain and simple," said Frank Reynolds, a commercial fisherman on Lake Erie who since the 1970s has been showing up at public meetings with a jar of walleye larvae to draw attention to the issue. "They're trying every way they can to avoid doing something to protect the fish."

The Tribune obtained thousands of pages of industry reports documenting power plant fish kills through Freedom of Information Act requests to the eight Great Lakes states and the U.S. Environmental Protection Agency. Michigan and New York provided only limited information, while Indiana failed to respond in time to be included in this story, but the available records highlight a threat to the Great Lakes ecosystem that has largely gone unaddressed for years.

Among the findings:

•The fish killed at the Point Beach nuclear plant north of Manitowoc, Wis., reduce the yield of Lake Michigan's fisheries by an estimated 10,625 pounds a year, or about 4.5 percent of the annual commercial fishing catch by weight.

•Across Lake Michigan from Chicago, the Cook nuclear plant near Benton Harbor, Mich., kills more than 1.3 million fish annually, most of which are yellow perch. An additional 196 million eggs and other organisms die each year inside the plant's cooling system. In Waukegan, the lone Illinois power plant on the lake kills up to 5.2 million fish a year.

•On Lake Erie, the Bay Shore coal plant near Toledo, Ohio, kills 46 million adult fish and more than 2.4 billion eggs, larvae and young fish each year in the region's most prolific spawning grounds. Less than 15 miles away, the Monroe coal plant in Michigan each year kills more than 25 million fish and 499 million eggs and other organisms on the western edge of the lake.

Federal law requires new power plants to install less-destructive equipment such as cooling towers, which act like a car's radiator and draw water only to make up for what is lost through evaporation. At the Nine Mile Point nuclear plant on Lake Ontario in New York, a reactor that has a once-through cooling system killed 154,541 fish in 2007, but a second reactor with a cooling tower killed just 34,128, documents show.

Industry lawsuits have delayed the phaseout of once-through cooling at older plants. Echoing their arguments about tougher air-pollution rules, power company lobbyists say the expense would force dozens of plants to close, costing jobs and making the nation's electrical grid less reliable. Some plants have tried to reduce fish kills by building intakes offshore away from spots where fish congregate. Others have installed systems designed to deter fish with sound or air bubbles.

"It's not clear to me scientifically that there is a broad-based problem out there that needs to be fixed," said C. Richard Bozek, director of environmental policy for the Edison Electric Institute, a trade group for energy companies. "There are situations out there that need to be addressed, but those decisions should be made on a site-by-site basis."

When Congress passed the Clean Water Act in 1972, lawmakers included a provision intended to help restore the Great Lakes and other U.S. lakes and rivers by forcing polluters to significantly reduce their water withdrawals. Faced with a court order, the Obama administration in March proposed new nationwide rules that will require older power plants either to meet certain limits on fish kills or to reduce the velocity of their water intakes.

However, the EPA would leave enforcement to state officials who have allowed cooling intakes to be used with few if any limits. The proposed rules also exempt companies from installing cooling towers at older plants when they are modified.

Nearly 60 percent of facilities affected by the federal proposal probably won't be required to make any changes, according to EPA documents. Agency officials are taking public comments until July 16 and expect to finalize the rules by July 2012.

"This proposal is a big disappointment — a punt to states that have neither the expertise nor the political will to take this on effectively," said Thomas Cmar, an attorney with the Natural Resources Defense Council.

State regulators say they are doing the best they can with insufficient resources and conflicting guidance from federal officials. The EPA declined requests for interviews with Administrator Lisa Jackson or other top officials, but in response to written questions, the agency said its proposal "establishes a strong baseline level of protection and then allows additional safeguards for aquatic life to be developed through a rigorous site-specific analysis."