Lake Manitoba, 4624 km2, elev 248 m, is one of 3 large lakes occupying the southern half of Manitoba. A narrow, irregular lake, about 200 km long with marshy shores, it is fed mainly from Lake WINNIPEGOSIS, which lies to the northwest, and drains northeast via the Dauphin River to Lake WINNIPEG. Delta Marsh at its southern end, which lies just 24 km north of PORTAGE LA PRAIRIE, is an important waterfowl research area. When Pierre LA VÉRENDRYE arrived in the mid-1730s, he found the area populated by Assiniboine. For many years it formed part of an important trade route along which furs were transported via Lake Winnipeg and the northern rivers to Hudson Bay. Subsequently a commercial fishery was established. Early French traders called it Lac des Prairies; the modern name probably refers to the Algonquian spirit MANITOU.