Contaminants in Fish

Manitoba is a world-class fishing destination. The province is home to over 100,000 lakes, many of which have excellent water quality. At least 95 freshwater fish species live in Manitoba waters. However, even in pristine water quality conditions, all fish contain small amounts of contaminants (e.g., metals and trace elements) from natural sources (e.g., soil and rock). Human activities can contribute contaminants to aquatic ecosystems which can be taken up by fish. Contaminants can accumulate in fish tissues resulting in concentrations many times higher than the concentration in water. In addition, certain contaminants can bioaccumulate or biomagnify up the food chain (highest concentrations in top predator fish such as walleye or northern pike); ultimately affecting wildlife and humans.

Consumption of fish is a healthy choice because they are a good source of proteins, vitamins, fatty acids, other nutrients, and minerals.  However, when the concentration of a contaminant(s) in fish exceeds a certain threshold, their consumption should be limited to reduce the risk to human health. In such cases, the Manitoba government provides fish consumption advice to protect public health.

Selenium

• The Manitoba government is advising people to limit their consumption of fish from Schist Lake (regardless of species) to no more than four meals per month, due to elevated concentrations of selenium.  
• A meal is considered 227 grams for an adult (about the size of a hand).
• Children and individuals who are pregnant are not known to be more sensitive to selenium. Children are smaller and their meal sizes will be smaller than an adult. As a rough guide, one meal of fish for a child is about the size of their hand.
• If you have questions about this advisory, please review the frequently asked questions.
• Selenium is an essential nutrient / trace element that plays a major role in the healthy functioning of all living organisms. Not having enough selenium in the diet, known as selenium deficiency, can have negative health effects. However, too much selenium can also have negative health effects. The range between selenium deficiency and excess is relatively narrow. 
• Schist Lake is located in Northern Manitoba near the town of Flin Flon, along the border between Saskatchewan and Manitoba.
• Selenium has been contributed to Schist Lake, in part, through mining activities underway at Hudbay Minerals Inc.  Recent fish sampling indicates that concentrations of selenium in fish from Schist Lake are elevated compared to historical monitoring. The Manitoba government is working closely with Hudbay Minerals Inc. to understand the sources of selenium and how to reduce concentrations in fish in Schist Lake. 
• Based on our current data, the risk of short or long-term health effects from consuming fish from Schist Lake is low.
• The Manitoba government will update consumption advice as more data become available, if needed.
• Additional information regarding selenium is available through the International Joint Commission Health Professionals Advisory Board: Selenium - Too Much of a Good Thing or Government of Canada information sheet on selenium and its compounds.

Mercury

• In the 1970s, the Manitoba government, in collaboration with Manitoba Hydro and Fisheries and Oceans Canada, began monitoring mercury levels in fish from Manitoba’s major water systems.
• The Manitoba government has developed brochures providing information regarding the safe consumption of fish caught in Manitoba waters as it relates to mercury. The most recent brochure is titled “Mercury in Fish & Guidelines For The Consumption of Recreationally Angled Fish in Manitoba”. 

Please direct any questions and comments to waterquality@gov.mb.ca.