NEW ORLEANS -- When he was a boy, Cliff Glockner and his friends went fishing and swimming in Lake Pontchartrain nearly every day.

"I used to sit under the oak trees here and eat my lunch after crabbing," said Glockner, 50, as he piloted his 25-foot fishing boat near the lake's north shore on a recent Saturday.

The oak trees are gone, however, victims of the pollution that is eroding Lake Pontchartrain's marshy shoreline and has diminished fish and shellfish catches. Slowly but steadily, the mammoth body of water that abuts New Orleans is dying.

But Glockner and hundreds of other fishermen and ordinary citizens want to stop the process. They founded the Lake Pontchartrain Basin Foundation earlier this year to try to clean up the lake. On Friday they achieved their first major goal when Gov. Charles "Buddy" Roemer banned the 50-year-old practice of dredging clamshells from the lake bottom, because of the pollution it caused.

"If we can get just half of {the lake} back, I'll be satisfied," said Glockner. "We can live with half of it, but we can't live with all of it destroyed."

The effort to clean up the lake is part of a growing environmental movement in what, according to several indexes, is the country's most industrially polluted state. Gov. Roemer, a Democrat who took office two years ago, is allied with the movement and has scored some victories, arguing that reducing pollution fosters economic development.

But he is having trouble overcoming a 60-year tradition in Louisiana of accepting pollution as the price for creating new jobs and attracting investment.

Paying this price is known here as "the devil's bargain" and was begun by Gov. Huey Long. The legendary Long funded social programs and public works projects by imposing taxes on the oil companies operating in the state. In return, he allowed them to operate with few controls.

The devil's bargain has taken its toll on the state's water, air and soil. Louisiana had the worst industrial pollution record in the nation in 1988, according to Environmental Protection Agency figures released in April. Chemical plants and other factories in Louisiana released 716 million pounds of toxic pollutants into the environment, 120 million pounds more than Texas, which was ranked second. Louisiana ranked first both in toxic pollutants draining into the water and seeping into underground wells. The state ranked fourth in air pollution emissions.

The 75-mile corridor between New Orleans and Baton Rouge, which is home to 78 chemical plants and refineries, is called "cancer alley." More than 500 abandoned hazardous-waste sites dot the state, and about 50 square miles of Louisiana's coastal wetlands disappear each year in part because canals dug for oil exploration let in saltwater from the Gulf of Mexico that kills vegetation.

The oil and chemical industries play down the damage and argue that the old policy is still a good approach for Louisiana. The Roemer administration's environmental proposals will force businesses to reduce investment and encourage them to locate elsewhere, industry representatives say.

"We have gone from a minimum of environmental regulation 20 years ago to over-regulation under the Roemer administration," said Michael Lyons, vice president of the Mid-Continent Oil and Gas Association, which represent the major oil companies.

The state legislature last year approved three major environmental bills pushed by Roemer. The measures mandate that toxic air emissions be cut in half by 1994, phase out oil and gas waste pits in wetland areas and fund a program to slow the disappearance of the coastal wetlands.

Through administrative action, the Louisiana Department of Environmental Quality began requiring oil and gas companies to test their discharges for radiation and toxicity. The agency also required corporations to check for ground water contamination before building plants and facilities.

Roemer's major environmental initiative this year called for sharply increasing taxes on the disposal of hazardous waste and using one-fourth of the $53 million to be raised by the tax per year to fund increased enforcement action.

But old habits die hard. With the still-powerful Louisiana Chemical Association flexing its muscles, a state House of Representatives committee has watered down the measure, reducing the proposed tax increase on hazardous waste entering underground wells and providing less enforcement money than Roemer sought.

The chemical association is also suing to block rules issued last year that reduced the amount of toxins that chemical companies can dump into Louisiana's rivers and lakes.

While industry groups say that Roemer's environmental measures will cost jobs and investment, Environment Secretary Paul Templet said that cleaning up the environment is good for business in the long run.

"We've lost a thriving recreational industry on the Tangipahoa River because of high fecal coliform counts," said Templet. "The commercial fisheries on the Calcasieu River are gone because of chemicals from PPG Industries. Two companies wanted to locate in Louisiana -- Formosa Plastics and Huntsman Chemical -- but didn't because of pollution. And building equipment to control pollution is an industry in itself."

Pollution from oil and gas drilling threatens Louisiana's $500 million fisheries industry, said Virginia Van Sickle, secretary of the Louisiana Department of Wildlife and Fisheries. "Half of the oyster beds are closed because of pollution," she said.

Environmentalists here, who were once derisively known as "tree huggers," now include mainstream people like Glockner.

Glockner has worked as a fisherman on Lake Pontchartrain for 30 years. His catch used to be crabs, shrimp, nutria, alligators and several types of fish. But all that is left to catch today are crabs and fish.

For years, surrounding communities have dumped raw sewage into the lake and allowed waste from everyday life -- such as motor oil -- to enter the lake untreated. Swimming is prohibited because of the high fecal coliform count.

Pesticides used on farmland have washed into rivers that drain into the lake, which is the fourth largest within U.S. borders.

With governments in communities surrounding the lake beginning to install wastewater treatment plants two years ago, the Lake Pontchartrain Basin Foundation had concentrated its anti-pollution effort on having the state prohibit clamshell dredging.

Studies have shown that dredging reintroduced into the lake's water heavy metals that had settled on the bottom, said Steve Cochran, the foundation's executive director.

Officials at Dravo Basic Material Corp., which operated the barges that dredged Lake Pontchartrain, disputed these findings. They argued that ending shell dredging will cost hundreds of jobs and sharply increase the costs of building roads in southern Louisiana, where the shells provide inexpensive roadbeds in marshy areas.

Dredging in Lake Pontchartrain and the Atchafalaya Bay has been a $71 million industry, said Anne Jordan, a Dravo spokeswoman. She said, however, that Dravo won't appeal the dredging ban in the courts.

Cochran concedes that prohibiting shell dredging will cost jobs and investment in the short term but said that many more jobs could be created by turning Lake Pontchartrain into a recreational mecca for boaters, divers, beach-goers and sailors.