Fish mercury studies in the Decho: 2013-2022

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Project Background

Fishers, community members, regulators, monitors, and scientists are interested in understanding the variation in mercury levels among fish in Dehcho lakes. This includes investigating why some lakes have relatively low mercury levels in their fish while others have relatively high mercury levels in their fish.

In certain Dehcho lakes, the presence of mercury, a metal released through both natural processes and human activities, has reached levels significant enough in fish to warrant consumption advisories. There is a concern that the fear of mercury might discourage people from consuming these fish, potentially worsening food security and negatively impacting community well-being.

To address these concerns and questions, Laurier researchers and community partners worked together to understand why lakes vary so much in their fish mercury levels, and which sources of fish are safest and healthiest to eat.

Outcomes

Since 2013, fifteen Dehcho lakes have been sampled for fish, water, sediment, and small organisms residing in both the water and sediment. This extensive sampling aimed to determine the age, diet, and mercury levels of each fish, as well as the amount of mercury in the small organisms and the chemistry of lake bottom sediment. Additionally, researchers utilized imagery to map the area and type of land that drains into each lake.

The study revealed that in the Dehcho region, different fish species exhibit varying mercury levels.

• Lake Whitefish displayed low mercury levels in all lakes and are a safe and healthy food source. Lake Whitefish have low mercury levels because they mostly feed on bugs.

• Northern Pike (jackfish) and Walleye (pickerel) exhibited higher mercury levels because they feed higher in the food chain.  However, there are still safe and healthy sources of pike throughout the Dehcho region.

Impacts

This new research aims to improve the accuracy of predictions regarding mercury levels in fish across the Dehcho region. The group's findings have revealed that fish mercury levels in Northern Pike can be predicted based on parameters such as catchment to lake area ratios, water quality parameters, and fish growth rates. These results also contribute to ongoing discussions about potential management strategies aimed at reducing mercury levels in fish. One such strategy is the concept of "fish-downs," which involves selectively harvesting specific numbers or types of fish, offering the potential to accelerate growth and lower mercury levels.

The group will continue its investigation into why the relationships between fish mercury and water chemistry vary among species and across lakes. The group will focus on understanding the rate and extent of changes occurring in the land surrounding the lakes, including permafrost thaw, in order to better predict future fish mercury levels. This will provide valuable insights into which lakes are most vulnerable to climate-induced alterations in fish mercury levels. Predicting how fish mercury levels may change in response to a warming climate remains a top priority.

Partners

• Dehcho Aboriginal Resource and Oceans Management Program (AAROM)
• George Low and Mike Low, Dehcho AAROM

More Information

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