Matheson Island is a community and an island located in the Canadian province of Manitoba, at the narrows of Lake Winnipeg. A designated place in Canadian census data, the community had a population of 136 in the 2021 Canadian census. Commercial fishing is the number one source of income for the community and area, the Matheson Island Marketin…Matheson Island is a community and an island located in the Canadian province of Manitoba, at the narrows of Lake Winnipeg. A designated place in Canadian census data, the community had a population of 136 in the 2021 Canadian census. Commercial fishing is the number one source of income for the community and area, the Matheson Island Marketing Co-Op works with approximately 110 local fishers.