Darius Stangu of the District shows off the second carp he fished out of the Anacostia River in Anacostia Park. He put both back. ‘I do catch and release. I don't eat them,’ he said. (Darryl Fears/The Washington Post)

Gary Oesby sat at a wobbly picnic table at the edge of the Anacostia River, two fishing poles leaning on thin tree limbs, lines in the cold water, stewed beef sweetened with vanilla extract balled up on both hooks, beckoning catfish to take their last bite ever.

Oesby, 53, retired, with mouths to feed at home in Southeast, sat patiently for more than an hour. “They’re not biting today,” he said on a recent Monday, “but it’s normally a good spot.” On other days, he claimed he’s caught 30 to 40 fish. Now he would be happy with a few, maybe some tasty channel catfish, the ones with the huge head. “I want to eat good.”

There are hundreds of anglers like him, District and Prince George’s County residents mostly, who throw lines in the Anacostia and pull out catfish, rockfish and carp for supper, according to a new study. But it says the fish — especially catfish, which bottom-feed in a toxic soup of muck — are contaminated with cancer-causing chemicals “that present a health risk” to the people who eat them.

“We can’t say eating catfish out of the river causes cancer,” said Dottie Yunger, a specialist at the Anacostia Watershed Society, one of several environmental groups that sponsored the study, released in October. “We know there are cancer-causing chemicals in the catfish. And we know that eating it over a long time can make you sick.”

Seventy-four percent of anglers in the study said they eat at least part of their catch, and most share it with people who take it home, sometimes to pregnant women and children. This is a major concern, because polychlorinated biphenyls (PCBs) and other cancer-causing chemicals detected in fish can affect a child’s mental development.

(Source: “Addressing the Risk: Understanding and Changing Anglers’ Attitudes about the Dangers of Consuming Anacostia River Fish,” by OpinionWorks)

Catfish were a focus of the study, “Addressing the Risk: Understanding and Changing Anglers’ Attitudes about the Dangers of Consuming Anacostia River Fish,” because they are more often found with cancerous tumors. Sixty-five percent of the 111 anglers interviewed said they caught channel catfish often, and 16 percent said they caught them sometimes. Thirty-three percent said they caught brown bullhead catfish often.

More than two-thirds of anglers who took part in the study were black, 18 percent were Latino and 8 percent were Asian. More than a quarter were born outside the United States. Nearly 65 percent said they fish the river at least once a week in warm weather.

They were less educated than most of the population — 62 percent had no more than a high school or equivalent diploma. A quarter had not completed high school.

Latinos, who often speak Spanish in various dialects from countries where there are no advisories, might regard signs saying eat no more than so many pounds of fish per month as silly, said Jorge Bogantes Montero, a natural resources specialists at AWS from Costa Rica. “You need someone to explain why.”

With a river system with a long history of pollution from sources such as the Navy Yard, the Washington Gas Light Co. and a landfill, the District issued its first consumption advisory in 1989. But only a few signs were posted in the District until after the new study’s release, Yunger said.

Now at least three stand beside the river in Anacostia Park. “Please do not consume your catch before consulting the advisory printed on your fishing license or online.” A few clicks on the D.C. Department of the Environment (DDOE) site leads to a stern public health advisory about fishing in the Anacostia, Rock Creek and Potomac River.

“Do not eat: Catfish, carp, or eel. May eat: One-half pound per month of largemouth bass, or one-half pound per week of sunfish or other fish,” it says. “The practice of catch and release is encouraged.”

Darius Stangu, a 37-year-old D.C. resident who fished for carp in Anacostia Park in early December, said he follows the warnings to the letter. “I only do catch and release,” he said. But if someone asks for his catch, he gives it to them and simply warns them not to eat too many.

“Sometimes ignorance is bliss,” Stangu said.

The Anacostia is so contaminated with toxins and bacteria that the D.C. Health Department forbids swimming and warns residents to scrub their hands if they so much as touch it.

At its bottom, a layer of midnight-black muck is more than six feet deep in places, a storage locker for PCBs and other harmful chemicals.

They include pollutants from dripping crankcase oil that runs from the road to the river in rain; car exhaust; carbons from industry smokestacks, wood and coal burning; and small chunks of pavement.

Catfish, carp and eels stick their mouths in the muck as they troll for worms and often develop cancers. Smaller bullhead catfish store the residue in the skin, making lesions that develop easy to see. But it is hard to detect problems in bigger channel catfish that store the residue in the muscle that people eat, said Fred Pinkney, a biologist for the U.S. Fish and Wildlife Service who analyzed Anacostia fish for the DDOE.

“You could have a beautiful-looking channel catfish and it could be loaded with PCBs and other cancer-causing chemicals,” he said.

But up and down the 8.4-mile tidal river that flows from the Maryland to the District and flows into the Potomac at Hains Point, anglers said they were confident about the health of the fish.

Most anglers in the study who heard about concerns over the health of fish got the news by word of mouth. Oesby and his family members were among those who have not heeded the city’s warning.

“My niece, I say to her, I want to put them back in the water. She say, ‘You better bring those things here.’ ” And Oesby does so, saying eating catfish “ain’t never hurt me.” He offered more evidence. “I know some more people eat them, they ain’t hurt.”

Mike Bolinder, the Anacostia riverkeeper — his organization is another sponsor of the study — shook his head during a recent interview. “They’re talking about food poisoning, we’re talking about cancer,” he said.

Bolinder said he has followed fishermen to their kitchens. They “have developed this visual detection to determine whether fish are clean or not,” he said. They look for dark blood, cloudy eyes, springy flesh. They soak the fish in vinegar and milk for several days to ward off ill effects, or fry it on a high flame to cook out toxic metals. None of this is based in science, he said.

In spite of the danger, Bolinder parts ways with environmentalists who believe fishing should be banned.

“I am so torn with the findings of the study,” he said. “I wouldn’t encourage someone to eat something bad for not only them but their children.

“But . . . how can you deny someone in need of free food, and what are the sociological impacts to taking away fishing? It is the most popular sport in America. Only walking is done more,” he said.