Mercury in N.W.T. lakes sparks health advisory

Higher than normal mercury levels in four lakes has the Northwest Territories top health official warning people to be careful about how much fish they eat from them.

Higher than normal mercury levels in four lakes has the Northwest Territories top health official warning people to be careful about how much fish they eat from them.

In a public health advisory issued Wednesday, Dr. Kami Kandola recommends that people limit the amount of fish they eat from Trout Lake and Cli Lake in the N.W.T.'s Dehcho region, as well as Lac St. Therese and Kelly Lake in the Sahtu region.

The higher mercury levels have a greater impact on bigger, predatory fish, such as lake trout and walleye, than on fish that are lower on the food chain, such as grayling and whitefish, Kandola said.

Built up in fat cells

"Some predatory fish, their levels of mercury in their fat and in their flesh can be thousands of times higher then the levels in the water around them," Kandola told CBC News on Wednesday.

Mercury builds up in the fish's fat cells, and there's no way they can get rid of that buildup, Kandola said.

"The more the fish they eat, the bigger they get," she added. "The longer they live, the higher the levels of mercury."

Kandola noted that the health benefits of eating fish outweigh any potential risks, adding that mercury levels vary from lake to lake and can be caused by natural or human activities.

Limit or avoid consumption

She recommends that people fishing on Trout Lake and Kelly Lake limit their intake of lake trout, especially trout more than 60 centimetres long.

People fishing in Kelly Lake or Trout Lake are generally advised to eat no more than 150 grams — or two servings — of fish a week. Children and pregnant women are being urged to eat even less trout from those lakes, keeping within 75 to 150 grams per month.

Dennis Deneron, acting chief of the Sambaa K'e Dene Band at Trout Lake, said he's not too concerned about the health advisory because people in his community don't eat predatory fish in the summer.

"This time of year, we don't really go fishing for trout or anything. We usually go for pickerel and whitefish and that," Deneron said.

"That's how we manage our fish here, is that we let go of the big ones and keep the smaller ones."

People are warned to avoid eating any predatory fish from Cli Lake and Lac St. Therese. Mercury levels in Lac Ste. Therese have nearly tripled from 1992 levels, according to the advisory.

Kandola said drinking water tests have not found elevated mercury levels.