Ernie Aldridge of Alto has been fishing off the waters of Lake Lanier at bridges, parks and shorelines since the late 1960s.

“I eat everything I catch out there if it’s big enough,” said Aldridge as he cast a line recently at Don Carter State Park in North Hall.

The lake’s waters “always look pretty clean to me,” he said.

Environmentalists say the occasional fisherman catching and eating fish from the lake — such as Aldridge, who visits about once a month — shouldn’t experience any health issues.

“Where we really see problems with eating fish are the people living off them, eating them every day,” said Jason Ulseth, who leads the Chattahoochee Riverkeeper.

The main worry is mercury, usually in the form of atmospheric deposits from faraway coal-burning power plants, he said.

Mercury deposits are based on wind patterns and other factors, he said.

“Typically, the bigger the fish is, the more accumulation of toxins, but that’s pretty much anywhere on the planet,” Ulseth said.

Typically, trout are safe to eat, as “they are bug eaters for the most part, and bugs don’t accumulate mercury,” he said.

“On the other hand, predatory fish like bass accumulate toxins as they eat smaller fish.”

Will Wagner, manager of Don Carter State Park, said a 3-pound rainbow trout was caught 6 miles upstream from the park.

“That is a great indicator species of clean water,” Wagner said.

Brooks Dacus of White County said he focuses primarily on catching trout.

“Usually when I’m fishing in the lake, I’m either playing with the bream or the carp,” he said.

During a recent visit to the state park, Paul Dyer of Auburn said he typically catches and releases fish. Growing up with his father working as a microbiologist, he said he is aware of hidden health concerns.

“I might eat the fish,” he said.

His wife, Kathryn, said she is less inclined to do so.

“I’ve just heard a lot about Lake Lanier not being (healthy),” she said.

The Georgia Environmental Protection Division and the state’s Wildlife Resources Division monitor fish tissue to determine how much of certain fish species are safe for eating.

Every year, they select locations throughout the state to sample for various game fish species, testing them for organic chemicals, pesticides and heavy metals, including mercury, officials said.

The state publishes fish consumption guidelines annually, with the 2015 edition due out soon.

Currently, Lake Lanier has consumption guidelines that recommend limiting consumption of largemouth bass, spotted bass, striped bass, carp and channel catfish to one meal per week because of mercury concentrations exceeding human health criteria.

Overall, “the lake has seen some changes over the years, but it looks like we’re on the right track,” said Forsyth County resident Dan Saknini, president of the Lanier Crappie Anglers Club and a member of the Lanier Striper Club.

Saknini, who has lived on Lanier for 15 years, is generally a “catch-and-release sort of a guy, but I think if the fish have issues, you can tell.”

“There’d be sores on the fish, which you don’t see that often,” he said. “Is it safe to eat? Definitely. If I eat fish, it may be once every other week and usually, it’s fresh fish from the lake.”

He said he wouldn’t necessarily eat fish from some creeks or streams feeding directly into the lake, such as Flat Creek, a largely urban waterway that flows from downtown Gainesville and past poultry processors.

“It stands out like a sore thumb,” Saknini said.

At the same time, he likes to fish in the backs of creeks.

In shallower water, “you will notice anything unusual ... a lot more than out in the open water,” he said.