Blackfin Cisco, (Coregonus nigripinnis). Field Museum of Natural History, Chicago. FMN H no. 13951. Conservation status: extinct. The decline of this species in the Great Lakes of North America was caused by overfishing, predation by sea lamprey, alewife and rainbow smelt and by Interbreeding with lake herring. By the early 1900's, stocks were so low that commercial fishing of the Blackfin Cusco was not viable. Occasional sightings are made in Lake Nipigon in northern Ontario and other localities but they are disputed and thought by some authors to be sightings of lake herring.