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High mercury levels found in fish
Consumption limits recommended for Northern pike,
walleye and trout from McGill, Deep and Fish lakesRoxanna Thompson Northern News Services Published Thursday, September 1, 2011
Mercury is present in McGill Lake and Deep Lake near Jean Marie River and Fish Lake near Wrigley. As a result, it's recommended that people eat smaller fish and fish that are lower in the food chain, such as whitefish or grayling, from the lakes while consuming fewer fish higher in the food chain, such as walleye, Northern pike and lake trout. "We know that fish is a good source of nutrition high in protein as well as vitamin B and omega fatty acids and we always want to make sure we balance out the risks and benefits of eating the fish," said Dr. Lorne Clearsky, the territory's chief public health officer. Mercury is a neurotoxin that interferes with the brain and nervous system. The effects of long term exposure include tremors, numbness in the fingers and toes and vision and memory loss. Mercury is a natural element that occurs everywhere in very low concentrations, said Clearsky. It can also be created by human activities such as burning fossil fuels. This process emits mercury into the air and it is later deposited in different locations, he said. Mercury levels are normally higher in older fish and fish that are higher in the food chain, said Clearsky. Health Canada has established guidelines for consumption of fish with mercury levels beginning at .5 parts per million (ppm). Pike at McGill and Deep lakes have an average of .83 and 1.15 ppm respectively compared to 1.25 and 1.21 ppm for walleye. At McGill Lake, pike larger than 74 cm and walleye larger than 38 cm should not be consumed. Fish under 43 and 22 cm respectively for the two species can be eaten without restriction. For fish between the two lengths, there are recommendations for portion size and frequency of consumption for adults, pregnant and breastfeeding mothers, and children of various ages. The advisory also includes recommendations for the other two lakes. Clearsky visited both Jean Marie River and Wrigley in late August to present the findings of the tests and to consult with community members about what information they wanted included in the advisory. Some residents were already following good practices, he said. "They already knew you don't eat older fish or bigger fish," he said. Aboriginal Aquatic Resource and Oceans Management (AAROM) conducted the sampling project that caught the fish that were tested from the three lakes. For McGill and Deep lakes, the project was a followup on earlier testing. In the late 1990s and early 2000s the Department of Fisheries and Oceans tested 12 lakes in the Deh Cho, including McGill and Deep, and some in the Sahtu for mercury. Subsequent studies found some of the levels had risen in the Sahtu, said George Low, the Deh Cho's AAROM co-ordinator. With consultation from the communities, a decision was made to retest some of the Deh Cho lakes to see if there would be similar findings, said Low. Fish were caught in McGill and Deep lakes in December 2010. The tests showed no significant change in the levels in the two lakes compared to 2000. The release of the advisory is timely because the lakes are primarily fished in the winter by trappers, said Low. This is the first time Fish Lake has been tested. The Pehdzeh Ki First Nation chief and council recommended it because it's the lake most commonly used by the community for fishing, he said. The advisory includes recommendations for consuming pike, which have an average of .67 ppm, and walleye, which have an average of .91 ppm, from the lake. Not enough lake trout were caught to make a recommendation. Low said AAROM will revisit the lake this fall and winter to get more samples. Testing of other lakes will be ongoing, said Low. Samples were caught in Ekali Lake this summer.
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