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Ecoregion Description


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Species Richness


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104: Upper Mackenzie

Major Habitat Type:

temperate floodplain rivers and wetlands

Author:

Mary Burridge and Nicholas Mandrak

Countries:

Canada

Boundaries:

This ecoregion occurs in eastern British Columbia, northern Alberta, northwestern Saskatchewan and southern Northwest Territories (NWT). It includes areas in the upper portion of the Mackenzie basin that are drained by the Hay and Slave rivers that flow into Great Slave Lake, the Peace River that flows into the Slave River, and the Athabasca River that flows into Lake Athabasca.

Drainages flowing into:

Drainages in this ecoregion flow into the Arctic Ocean via the Mackenzie River.

Main rivers or other water bodies:

The Hay River begins in the Rocky Mountains in British Columbia, drains much of northwestern Alberta and empties into the western arm of Great Slave Lake in the NWT. The Peace River, 1923 km long, was formed by the merging of the Finlay River from the north and the Parsnip River from the south in eastern British Columbia. Other tributaries of this river include the Halfway, Beatton, Pine, Pouce Coupé, Smoky and Wabasca. The Peace River continues to flow through Wood Buffalo National Park and joins the Slave River in the northeast corner of Alberta. The Slave River, 415 km long, connects lakes Claire and Athabasca with Great Slave Lake. The Athabasca River, 1231 km long, begins in the Columbia Icefields in Alberta and flows northeast to empty into Lake Athabasca. Its main tributaries are the Pembina, Lesser Slave and McLeod rivers.

Lake Athabasca, located in northeast Alberta and northwest Saskatchewan, is fed by the Athabasca River and drains north via the Slave River into Great Slave Lake. Smaller tributaries of Lake Athabasca include Old Fort, William and MacFarlane rivers. Lake Claire is an isolated western extension of Lake Athabasca. It is fed by the Birch and McIvor rivers and drains via Mamawi Lake into Lake Athabasca.

Topography:

The foothills of western Alberta rise above the plains, mainly as linear ridges, rolling plateau remnants, and broad valleys. To the east, the ecoregion is underlain by Cretaceous shale and covered with undulating glacial till. The sloping land surrounding the Peace River is underlain by sandstone and shale and is covered by sediments of sand and till. The Slave River lowland is underlain by relatively level Palaeozoic carbonates forming sandy plains, or limestone bedrock covered with silts, clays and extensive peat deposits.

Climate:

This ecoregion lies in the continental subarctic climate zone (Köppen 1936). Total annual precipitation varies from around 300 mm in the north to over 450 mm in the south.

Freshwater habitats:

Many of the rivers in this ecoregion begin as fast-flowing streams with headwaters in the Rocky Mountains. Much of the ecoregion to the east of the Rockies is classified as wetlands. The Peace River cuts deeply through the plains of northern Alberta and, in certain locations, the valley extends up to 11 km in width. The Slave River has a winding, multi-channeled course through the flat terrain of the Canadian Shield before entering the grassy wetlands of the delta on the south shore of Great Slave Lake. The Peace and Slave rivers and lakes Athabasca and Claire form the Peace-Athabasca Delta, one of the largest inland freshwater deltas in the world. 

The Athabasca River begins in the Columbia Icefields in Jasper National Park where it is recognized as a Canadian Heritage River. The river flows through mountains with gorges, rapids, waterfalls and narrow channels before opening into wide, braided streams with alluvial flats. It winds through prairies and muskeg before entering Wood Buffalo National Park and Lake Athabasca. 

Great Bear, Great Slave, Lake Athabasca and a chain of lakes between them are remnants of a single postglacial lake. Lake Athabasca is at the edge of the Precambrian Shield and is a cold, deep lake. Lake Claire was also once a clear, deep lake but has become much shallower due to siltation.

Terrestrial Habitats:

This ecoregion intersects the following terrestrial ecoregions: Alberta-British Columbia Foothills Forests, Canadian Aspen Forests and Parkland, Mid-continental Canadian Forests and the Muskwa-Slave Lake Forests. Along the Hay and Athabasca rivers, vegetation is transitional between boreal and Cordilleran, and is characterized by mixed forests of lodgepole pine (Pinus contorta), quaking aspen (Populus tremuloides), white spruce (Picea glauca), balsam poplar (P. balsamifera), paper birch (Betula papyrifera) and balsam fir (Abies balsamifera). Black spruce (P. mariana) and tamarack (Larix laricina) are found in wet sites. Vegetation along the Peace River drainage includes large stands of quaking aspen (Populus tremuloides), followed to a lesser extent by balsam poplar (P. balsamifera). Jack pine (Pinus banksiana) stands may be found in dry, sandy areas. To the south of Great Slave Lake is a continuous mid-boreal mixed coniferous and deciduous forest extending from northwestern Ontario to the foothills of the Rocky Mountains. This forest includes quaking aspen (Populus tremuloides), balsam poplar (Populus balsamifera), white and black spruce (Picea glauca and P. mariana), and balsam fir (Abies balsamea), with ericaceous shrubs (Ericaceae) and mosses.

Fish Fauna:

This fish fauna is a mix of secondary freshwater fishes such as chars (Salvelinus spp.) and whitefishes (Coregonus, Prosopium spp.), and a variety of primary freshwater fishes (e.g. northern pike (Esox lucius), minnows (Cyprinidae), and suckers (Catostomidae)). The primary freshwater species are indicative of the Mackenzie River as a post-Wisconsinan dispersal corridor between the Beringian and Mississippian Wisconsinan refugia. As the result of the falls separating this ecoregion from the Lower Mackenzie [105] ecoregion, the Upper Mackenzie lacks some of the anadromous fishes (e.g. Pacific salmons (Oncorhynchus spp.) and whitefishes (Coregonus spp.) found in the latter ecoregion.

Description of endemic fishes:

No known endemic species.

Ecological phenomena:

As the result of physical barriers, the species in this ecoregion generally do not exhibit diadromy. The Peace-Athabasca Delta, recognized as a Ramsar wetland complex of international importance, is one of the largest inland freshwater deltas in the world.

Evolutionary phenomena:

Morphological radiation related to depth and prey has been identified in lake trout (Salvelinus namaycush) and cisco (Coregonus artedi) in Great Slave Lake.

Justification for delineation:

The ecoregions of Canada were identified based on the faunal similarity of 166 major watersheds based on a cluster analysis of freshwater fish occurrences in these watersheds. The Upper Mackenzie ecoregion includes the upper Mackenzie River watershed. The fish fauna of the Mackenzie watershed is a mix of fishes from the northwestern Berinigian refugium and southern Mississippian refugium. However, it has a lower diversity than the Lower Mackenzie [105] ecoregion, as the falls separating the two ecoregions prevent the upstream migration of some diadromous species.

Level of taxonomic exploration:

Fair / Poor

References/sources:

Abell, R., Olson, D., et al. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.

Eswg (1995) "A national ecological framework for Canada". Ottawa/Hull, Ontario, Canada. Agriculture and Agri-food Canada, Research Branch, Centre for Land and Biological Resources Research; and Environment Canada, State of the Environment Directorate, Ecozone Analysis Branch..

McPhail, J. D. and C. C. Lindsey (1970). "Freshwater fishes of northwestern Canada and Alaska" Fisheries Research Board of Canada Bulletin 173 381.

McPhail, J. D. and R. Carveth (1992) "A foundation for conservation: the nature and origin of the freshwater fish fauna of British Columbia". Field Museum, Department of Zoology, University of British Columbia..

Nelson, J. S.,Paetz, M. J. (1992). "The fishes of Alberta" 2. Edmonton, AB: University of Alberta Press.

Ricketts, Taylor H. Dinerstein Eric Olson David M. Loucks Colby J. (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.

Rowe, J. S. (1972) "Forest Regions of Canada". Ottawa. Canadian Forest Service, Department of Environment..

Scott, W. B.,Crossman, E. J. (1998). "Freshwater fishes of Canada" Fisheries Research Board of Canada Bulletin 184 966 + xvii..

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