The blackfin cisco (Coregonus nigripinnis) is a member of the whitefish sub-family. This silvery, deep-bodied fish with black fins, large eyes, a blunt snout and a terminal mouth, is one of the largest species of ciscoes.
It is a dark silvery color, with a dark green to black back, and pink or purple on the sides; the outer half of the fins is black. Blackfin ciscoes measure up to 510 mm (21 inches in length). Its preferred habitat is cold lakes at depths of up to 180 metres. The blackfin cisco was last seen in Lake Michigan in 1969 and in Lake Huron in 1960. Various sources state that the blackfin cisco is still occasionally sighted in Lake Nipigon in northern Ontario, and the status of the species in Canada and Ontario is still under review. However, the IUCN Red List lists it as extinct.
The decline of the species has been largely caused by overfishing and predation from the invading sea lamprey. The introduced alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) are also aggressive predators of juveniles. Blackfin ciscoes were commercially fished until the early 1900s when declining stocks made the fishery uneconomic. Current threats to the only remaining population include commercial fishing, predation by rainbow smelt and interbreeding with lake herring (Coregonus artedi).