Ontario Fish Mercury Levels On The Rise

By on March 8, 2016
Walleye. (Credit: U.S. Fish and Wildlife Service / Public Domain)

Levels of mercury in Ontario fish are on the uptick, according to new research out of the University of Toronto. If the trends continue, there could be considerable consequences to human health as well as the economy, researchers say.

Fish mercury levels actually went down during the 1970s and 1980s, but mercury levels in walleye and pike have increased between 1995 and 2011. The concern is that continued rises could pose significant health risks to both fish and those who consume them.

To assess the trends, scientists looked at mercury levels found in Ontario walleye, northern pike and lake trout over the past 15 years while projecting where levels could be in 2050.

Walleye, northern pike and lake trout were chosen as subjects because they are top predatory fish and tend to accumulate higher concentrations of mercury from eating contaminated prey lower in the food chain. The fish are also extremely popular among anglers and contribute significantly to Ontario’s commercial, sport fishing and tourism industries, adding about $2.2 billion to Ontario’s economy annually.

Data used in the study were obtained from the Fish Contaminant Monitoring Program, a long-running program in Ontario. It covers a large geographical area, covering more than 200,000 measurements of fish mercury levels taken across the province, even including some remote locations only accessible by plane.

A researcher with the Ontario Sport Fish Contaminant Monitoring Program holds a Walleye and Northern Pike. (Credit: Fish Contaminant Monitoring Program)

A researcher with the Ontario Sport Fish Contaminant Monitoring Program holds a Walleye and Northern Pike. (Credit: Fish Contaminant Monitoring Program)

Northern Ontario lakes in particular are showing trends of increasing fish mercury levels. If the levels continue to increase at this pace, walleye at almost all monitored Northern Ontario lakes will suffer sublethal effects including an inability to reproduce.

The study also looked at the impact rising mercury levels may have on fish consumption advisories. It shows that, by 2050, only 1 percent to 33 percent of monitored Ontario lakes may have walleye in which mercury levels could be deemed safe to eat twice a week, the recommended serving of fish by Health Canada to maintain a healthy diet.

The findings, published in the journal Environmental Science & Technology, build on a 2014 study that found mercury levels in the same fish have been on the rise over the last 15 years.

Mercury emissions in North America have been in decline, especially in Canada where rates fell 90 percent between 1970 and 2011. North American emissions now represent only about 3 percent of human-caused global mercury emissions.

Global coal burning and mercury emissions have actually gone up in the last 20 years due to greater industrialization in China and India. Current global emissions of mercury stand at about 2,000 metric tons annually.

Mercury is a highly toxic pollutant that’s been shown to disrupt sex hormones in fish while in humans causing damage to the neurological, immune, genetic, cardiovascular, respiratory and gastrointestinal systems.

Top image: Walleye. (Credit: U.S. Fish and Wildlife Service / Public Domain)

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