Commercial fishing on the North Shore began to surge in the mid-1830s when the American Fur Company established fishing stations to meet demand for Lake Superior whitefish. Although that effort ended in 1842, travel books and visitors' accounts spoke of a seemingly inexhaustible fish supply that attracted many settlers. Scandinavian immigrants began North Shore fishing businesses in the 1890s, and by 1899 millions of pounds of lake trout, whitefish, and herring were caught by line or taken in gill nets set in open water or under the ice. In 1915, the Duluth area alone harvested a record 10,000 tons of fish. Between 1920 and the 1960s, fish populations declined because of overfishing, industrial pollution, and the arrival of the parasitic sea lamprey, which entered the Great Lakes in 1938 through shipping canals and caused severe losses of native fish, though its numbers are controlled. During the past thirty years, Lake Superior's fishery has recovered through stocking, natural rebound, sustainable harvest, and lamprey control. Today, commercial fisheries harvest lake trout, whitefish, herring, chubs, siscowet, and smelt, while lake trout and salmon support sport fishery.