The species was first mentioned by P.R. Hoy 1872, attributing Gill as the species authority, but Gill's manuscript was never published. The first valid description of this species is attributed to James Wood Milner in 1874. The taxonomy of C. nigripinnis, along with other ciscoes in the C. artedi complex, is unresolved. C. nigripinnis was recognized by W.N. Koelz in 1929 to consist of four subspecies, but he had difficulty distinguishing some specimens from C. kiyi. The subspecies he named were C. n. nigripinnis in Lake Huron and Lake Michigan, C. n. cyanopterus in Lake Superior, C. n. prognathus in Lake Ontario and C. n. regalis in Lake Nipigon. C. n. cyanopterus was later synonymized with C. zenithicus, and C. n. prognathus was declared a nomen dubium. Specimens from inland lakes in central Canada are generally regarded to be C. artedi. Turgeon and Bernatchez proposed in 2003 to merge several cisco species, including the blackfin cisco, into the taxon C. artedi sensu lato.
Description
It was a dark silvery color, with a dark green to black back, and pink or purple on the sides; the outer half of the fins was black. Blackfin ciscoes measured up to 510 mm. Its preferred habitat was cold lakes at depths of up to 180 metres.
Decline
The decline of the species has been largely caused by overfishing which occurred the 1950s which was the result of mismanagement in an unregulated fishery and predation from the invading sea lamprey. The introduced alewife and rainbow smelt 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. The blackfin cisco was last seen in Lake Michigan in 1969 and in Lake Huron in 1960. The latest was seen in 2006 in Long Lake near Thunder Bay. This species may still be extant in Lake Nipigon. The IUCN Red List lists it as extinct in 1996. The Committee on the Status of Endangered Wildlife in Canada listed it as threatened in 1988 and as data deficient in 2007, due to the uncertainty of its taxonomic status. Efforts are being made to consider reintroducing populations of cisco into the Great lakes specifically Lake Michigan.
