Boundaries

This ecoregion encompasses northeastern Manitoba, northern Ontario, and western Quebec, and is bounded by the headwaters of the rivers flowing into Hudson Bay and James Bay from the west and south.

Topography

Inland, this region has undulating glacial deposits with occasional hummocky bedrock ridges and knolls. Archean rocks form steeply sloping uplands around Churchill River. Toward the Hudson and James Bay coasts are vast lowlands underlain by flat-lying Palaeozoic limestone bedrock. Continued uplifting of the land surface due to isostatic rebound has created belts of raised beaches.

Freshwater habitats

The Southern Hudson Bay is located on the ancient rock of the Canadian Shield, and the process of deglaciation at the end of the last Ice Age left hundreds of interconnected lakes and watercourses. The central part of the Southern Hudson ecoregion, particularly the watersheds of the Winisk, Severn, Attawapiskat, and Albany rivers, is dominated by wetlands. Much of the Hudson Bay lowlands was flooded by saltwater following the retreat of the glaciers, and then subsequently drained as the result of isostatic rebound and lower sea levels. This left saltwater pools, which over time, were replaced by rainfall; species that were once trapped in the pools became adapted to freshwater.

Terrestrial habitats

Forests are dominated by black spruce (Picea mariana) and jack pine (Pinus banksiana), with shrubs (Ericaceae) and a ground cover of moss and lichens. Trembling aspen (Populus tremuloides), white birch (Betula spp.), white spruce (Picea glauca), balsam poplar (Populus balsamifera), and balsam fir (Abies balsamea) are present in some locations. The Hudson and James Bay coastline supports white spruce, alternating with fens and peat plateaus. Here, stunted black spruce and tamarack dominate the vegetation. The shrubs include dwarf birch (Betula spp.), willow (Salix spp.), and northern Labrador tea (Ledum decumbens).

Description of endemic fishes

There are no known endemic fish, mussels, crayfish, or aquatic herpetofauna.

Ecological phenomena

Arctic charr and brook trout exhibit anadromy, and lake sturgeon (Acipenser fulvescens) exhibits long-distance migrations in rivers within this ecoregion.

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 Southern Hudson Bay ecoregion is comprised of the watersheds draining into southwestern Hudson and James bays. The fish fauna of this ecoregion is depauparate as a result of limited direct connections to glacial refugia, marine inundation following the last Ice Age, and its harsh climate. Due to its proximity to Hudson Bay, there are many saltwater tolerant species in this ecoregion.

Level of taxonomic exploration

Poor