Summary of Assessment
Moderate changes to aquatic ecosystem health have occurred in the Mackenzie Great Bear sub-basin, according to most indicators considered in the assessment. Climate change was identified as a key driver of aquatic ecosystem change in the sub-basin, mainly through warmer winters that resulted in higher winter and spring stream flows.
Water Quantity
- Lower water levels in many waterbodies observed by Indigenous communities.
- Seasonal changes in monitored flows (increased winter and spring flows).
- Warmer air temperatures, especially in winter.
Habitat & Species
- Less healthy fish and changes in fish populations reported by traditional harvesters.
- New fish species are present and more commonly sighted (such as chum salmon) due to range expansion.
Water Quality
- Higher observed levels of turbidity and sedimentation in the Mackenzie River.
- Increasing trends in ions and potential increasing trends in some dissolved metals in scientific monitoring data.
Health & Wellbeing
- Changes in aquatic ecosystems have disrupted travel routes and access to harvesting areas and raised concerns about the potential contamination of water and country foods.
Water Quantity
- Lower water levels in many waterbodies observed by Indigenous communities.
- Seasonal changes in monitored flows (increased winter and spring flows).
- Warmer air temperatures, especially in winter.
Water Quality
- Higher observed levels of turbidity and sedimentation in the Mackenzie River.
- Increasing trends in ions and potential increasing trends in some dissolved metals in scientific monitoring data.
Habitat & Species
- Less healthy fish and changes in fish populations reported by traditional harvesters.
- New fish species are present and more commonly sighted (such as chum salmon) due to range expansion.
Health & Wellbeing
- Changes in aquatic ecosystems have disrupted travel routes and access to harvesting areas and raised concerns about the potential contamination of water and country foods.
Water quantity in the Mackenzie Great Bear sub-basin has undergone moderate change overall. Based on Indigenous and scientific observations, the sub-basin is subject to significant reductions in snow and ice cover, slightly earlier river ice break-up, and reduced spring river peak flows since the 1970s. These are likely linked to significant changes in climate over the past few decades, such as increased temperatures, particularly in winter. Human water use within the sub-basin has negligible impacts on water quantity due to the small population and large water yield in this sub-basin. Annual average river flows have mostly been stable, but winter and spring river flows have increased by up to 2% per year. The observed changes have potential to impact aquatic ecosystems and the ability for Indigenous communities to practice traditional land uses in the Mackenzie Great Bear sub-basin.
Read more about Snow & Ice, Water Flows & Levels, Climate and Water Use
Changes in water quality have been observed in parts of the Mackenzie Great Bear sub-basin, and for some water characteristics, affect the ability of some Indigenous communities to practice traditional land uses. Elders and harvesters from the Mackenzie River Delta and Dehcho regions have observed warmer water temperatures than experienced in the past, as well as murkier water in the Mackenzie Delta and changes in the color, smell and taste of the Mackenzie River. Scientific analyses have detected increasing trends in a few dissolved metals in recent years. The downstream effects of industrial development are a concern for local communities in the sub-basin. Although the Canadian Water Quality Index showed little impairment in the Great Bear River and in the Mackenzie River at Tsiigehtchic, it did show some impairment at Norman Wells.
Read more about Water Quality, Benthic Invertebrates, Land Use and Effluent Discharges
Aquatic habitat and species within the Mackenzie Great Bear sub-basin are undergoing moderate change. However, this assessment is primarily based on observations of changes in fish populations, health and fishing practices reported by Indigenous communities. Fish are considered key species for supporting ecosystems and remain a core part of local diets, livelihood and culture. New species like salmon and char have been observed, and a surge in populations of predatory fish like northern pike (Esox lucius) is thought to be shifting the balance of predator to prey species. Stocks of lake trout and Rat River Dolly Varden char (Salvelinus malma) have previously shown signs of population decline, and some fishers report catching less burbot (Lota lota) than in the past. More recent studies on lake trout in Great Bear lake indicate improved stock status. Reports of less healthy and skinnier fish with “softer” flesh and irregularities like sores and lumps have been made. Mercury levels in the tissue of subsistence fish species like Walleye (Sander vitreus) and burbot (Lota lota) have been examined and advisories on fish consumption have been issued in some lakes. Communities across the sub-basin have expressed concern for the health and sustainability of fish populations and many have adapted their fishing practices. Some Sahtu and Dehcho communities consume less fish than in the past due to concerns for elevated mercury levels, and the Gwich’in use a larger net mesh to reduce catching smaller fish and assist in ongoing efforts to restore char populations. Although this assessment includes scientific data for some fish species, limited data was found for Arctic fish stocks. Indigenous Knowledge and scientific observations of changes in wetlands and riparian forests in the sub-basin were not found.
Read more about Fish, Wetlands and Riparian Forests
Changes in aquatic ecosystem health in the Mackenzie Great Bear sub-basin are having moderate impacts on the health and wellbeing of local Indigenous communities. Health and wellbeing are closely linked to access to traditional foods. Some Indigenous communities report consuming less fish than in the past in response to declines in fish populations and concerns about unsafe levels of mercury. Similarly, other communities report a reduction in access to preferred traditional resources and fishing areas given the increased frequency of landslides, permafrost slumps, and lower water levels. Limitations on access and consumption of traditional foods impacts the health and wellbeing of many communities through changes in diets, food security, and reduced opportunities to engage in fishing practices and a traditional way of life. A low availability of scientific data for levels of country food consumption was found.
