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.

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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