Landings of brown shrimp in both Louisiana and Texas declined steadily after peaking at 103.4 million pounds (46.9 million kilograms) in 1990, sliding as the hypoxia zone expanded, according to a 2001 study by Roger Zimmerman and James Nance of the National Oceanic and Atmospheric Administration.

Size Correlation

The study found that the larger the zone, the smaller the shrimp catch. The average size of catches by weight dropped about 23 percent between the late 1980s and the 1990s.

An Environmental Protection Agency task force of scientists, state agencies and federal agencies set a goal in 2001 of reducing the Dead Zone to 2,000 square miles.

Little has been done with the group's recommendations, Rota said. Steps should include giving farmers more incentives to cut fertilizer runoff and reducing pollution from wastewater treatment plants, he said.

The drumbeat of support for ethanol, backed by subsidies, puts that goal of reducing the zone further out of reach, Rabalais said. Refiners, fuel distributors and retailers receive a federal tax credit on each gallon of ethanol blended with gasoline, and every state except Alabama offers additional subsidies.

"The rah-rah sort of drowns out the environmental side," she said. "If our federal government subsidizes more corn, they're working against water quality."

Shift to Corn

Ron Litterer, first vice president of the National Corn Growers Association, is among farmers who planted more of the crop this year. On his farm near Greene, Iowa, where he used to split his 1,500 acres (600 hectares) evenly between corn and soybeans, this year he devoted two-thirds to corn.

"We certainly want the family farmers to do well, but not at the expense of our natural resources in Louisiana and our family fishermen," said Tracy Kuhns, executive director of the Louisiana Bayou Keeper, a water-quality group. "It just seems there ought to be ways to reduce nitrogen use and purify that runoff prior to it making its way into the river."

The Gulf of Mexico isn't the only body of water with a Dead Zone. While its hypoxia area is a large one, the North Sea, the Chesapeake Bay and others also are afflicted. Hypoxia is blamed for the collapse of lobstering in Norway's Kattegat and the loss of fisheries in the Black Sea and Baltic Sea.

Staying Closer

Clint Guidry, a third-generation shrimper based in Lafitte, Louisiana, said he has felt the impact. It wasn't economical to fish farther offshore, past the Dead Zone, so in 1997 he sold his 97-foot boat. Now he works closer to the coast, catching smaller shrimp from a 35-foot skiff.

Rota likened the situation to the Gulf oil and gas boom, in which pipelines and other equipment cutting through the coast allowed saltwater to destroy wetlands.

"We've been basically a sacrifice zone for the nation," Rota said.