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.

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.