A recreational fisherman says the numbness and tingling in his hands and feet — nerve damage from mercury poisoning — were caused by catching and eating St. John River fish.

David Addleman has been consuming fish caught in the Mactaquac Dam headpond for nearly 40 years.

But last year he stopped the practice, after his neurological symptoms led his family doctor to discover toxic amounts of mercury in his blood.

"It was much higher than it should have been," Addleman said. "Three times normal."

Searched for source

Addleman, a retired psychiatrist living in Keswick Ridge, said his wife also tested positive for high levels of the heavy metal.

His doctor referred him for consultations. He also had public health officials join in the search for the source, including testing the couple's well water and going through his dietary habits. They found nothing.

He said he and his doctor suspected it was the fish he was catching and bringing home to eat.

During the months of July and August, Addleman estimates he would eat smallmouth bass or pickerel caught in headpond waters about once a week.

David Addleman says after he experienced neurological symptoms, his family doctor tested his blood and found the mercury levels to be three times higher than what they should be. (Mike Heenan/CBC)

Headpond mercury

Health Canada says food chains near dams can have higher mercury levels. On its website, the department says mercury can leach from flooded soil at hydroelectric dam sites or from any flooded areas.

"This process can add to mercury levels in freshwater aquatic food chains in those areas," the department says. "The consumption of mercury-contaminated fish is one of the main pathways for mercury exposure in humans."

In its annual fishing guide, the New Brunswick Department of Energy and Resource Development warns that many freshwater fish, including smallmouth bass and pickerel "should be limited to one meal every two weeks" for men and for women past childbearing age.

But it also notes "an occasional meal which exceeds guidelines should have no adverse effects."

Addleman said he was aware of the guidelines and knew to limit his consumption but never considered the amount he and his wife ate to be even remotely hazardous.

"I didn't think I had been going over the recommendations, but who keeps careful track? It's a short season."

The pair stopped eating fish completely. Six months later, their mercury levels returned to normal, but Addleman's symptoms remain.

David Addleman stopped eating fish he caught in the Mactaquac headpond after he developed neurological symptoms and learned he had toxic amounts of mercury in his blood. 1:33

He inquired about testing a few of the fish for mercury at a lab in Fredericton. He said RPC, a material-testing laboratory and fish health lab, informed him that while it could test the fish, the University of New Brunswick had already completed a preliminary study into mercury levels in fish in the headpond.

Instead of getting his fish tested, Addleman set about tracking down the researchers and met with Allen Curry of the Canadian Rivers Institute, based at the University of New Brunswick, a few months ago.

"They were willing to sit down and talk to me and share what some of their findings were," said Addleman. "The levels were well above what Health Canada would say are permissible."

Preliminary report

The report Addleman referred to is the "Preliminary Report on Mercury in Fish Upstream and Downstream of the Mactaquac Generating Station."

The report, dated Sept. 5, 2018, states on its opening page: "It is a preliminary report designed to inform future studies and it is not intended to be advice for the fish consumption by humans."

The report says three species, striped bass, muskie and shortnose sturgeon, were found to have mercury above Health Canada's maximum allowable levels for chemical contaminants in foods.

Smallmouth bass were also found to have mercury levels that exceeded Health Canada's guidelines for safe consumption by humans, according to Karen Kidd, a UNB biologist and one of the authors of the report.

A preliminary report by the Canadian Rivers Institute found high levels of mercury in some species of fish above and below the Mactaquac headpond, about 35 kilometres west of Fredericton. (Shane Fowler/CBC)

The report acknowledged small sample sizes and recommended further research before drawing conclusions.

'Restrict consumption'

"We saw some fish, like the muskie, and the smallmouth bass, and some shortnose sturgeon, and the striped bass that did have levels of mercury above the .5 parts per million guideline," said Kidd.

"And that would suggest that people who are eating them should be aware that they want to restrict their consumption."

Kidd said depending on the species, mercury levels were recorded at two to three times higher than what would be acceptable for consumption by Health Canada.

But those levels are not surprising, she said, and fall in line with similar studies done elsewhere in Canada near hydroelectric dams. She noted that headponds often lead to higher mercury levels in larger fish and predatory fish.

NB Power report

NB Power owns and operates the Mactaquac hydroelectric dam that forms the headpond Addleman has been fishing in.

The study was completed under the Mactaquac Aquatic Ecosystem Study. It's part of the Mactaquac Hydro-Electric Generation Station Renewal Project done in partnership with NB Power.

CBC News made several attempts to speak with someone at NB Power about the possibility of high mercury levels in headpond fish, but no one was made available for an interview.

The concluding line of the report said more comprehensive study is warranted. Kidd said she wants to follow it up by looking at mercury levels in more species, and by studying larger numbers of fish among the species already noted in last year's report.

The construction of the Mactaquac Dam led to the creation of the headpond waters, a process Heath Canada says can lead to mercury poisoning in fish. (Shane Fowler/CBC)

When Addleman sees other anglers casting their lines in the headpond, he immediately wants to rush over and warn them.

Any anglers he has talked to have been oblivious to the risk, he said.

Request for signs

He wants NB Power to place signs around the dam, warning of possible mercury poisoning, and better information from the Health Department.

Kidd agrees people need to better understand mercury consumption from wild fish and would also like to see signs in areas anglers frequent.

"There's a need for more public awareness and public communication," Kidd said. "In the fishing guide, there's certainly information on mercury, but it's found on page 42."

Addleman said he's telling his story now to warn other recreational fishermen before the season for smallmouth bass begins in this area July 1.

"I'm sure that most people aren't that aware of the risks," he said.