Underwater View of the Mnjikaning Fish Weirs National Historic Site of Canada in Atherley, Ontario

Mnjikaning Fish Weirs National Historic Site of Canada is located on portions of the bottom of the Narrows between Lakes Simcoe and Couchiching, a part of the Trent-Severn Waterway. This includes the navigable marked channel, the old channel that runs to the northeast and marshland surrounding these channels. The constriction of the Narrows allows fish to be caught as they move between the lakes, and the shallowness of the channel permits wooden weirs to be built there.