The longjaw cisco was a deep water cisco

Cisco (fish)

The ciscoes are salmonid fish of the genus Coregonus that differ from other members of the genus in having upper and lower jaws of approximately equal length and high gillraker counts...

 or chub

Chub

The European chub , sometimes called the round chub, fat chub, chevin, pollard or simply "the" chub, is a freshwater fish of the family Cyprinidae...

, usually caught at depths of 100 metres or more from Lakes Huron

Lake Huron

Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

, Michigan

Lake Michigan

Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...

, and Erie

Lake Erie

Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...

. Its Latin name was derived from Alpena

Alpena, Michigan

Alpena is a city in the U.S. state of Michigan and the county seat of Alpena County. It is considered to be part of Northern Michigan. The Thunder Bay National Marine Sanctuary is located in the city. The population was 10,483 at the 2010 census...

, a city in Michigan. Silver colored and growing to a maximum length of about 30 centimeters (12 inches) long, the extinction of longjaw cisco was a result of overfishing

Overfishing

Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

, pollution

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 of the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 and the disruption of Great Lakes food chains after the introduction of the sea lamprey

Sea lamprey

The sea lamprey is a parasitic lamprey found on the Atlantic coasts of Europe and North America, in the western Mediterranean Sea, and in the Great Lakes. It is brown, gray, or black on its back and white or gray on the underside and can grow up to 90 cm long. Sea lampreys prey on a wide...

.

The systematics of the group of fishes called "ciscoes" is complicated and scientists now generally believe that the longjaw cisco was not a separate species, but a distinctive population of large-bodied individuals of shortjaw cisco

Shortjaw cisco

The shortjaw cisco is a deepwater cisco or chub . It has large, smooth scales and is iridescent silver, with a greenish back and white belly. The mouth is small and toothless, and the lower jaw is shorter than or equal in length to the upper jaw...

 (Coregonus zenithicus).

The deepwater cisco fishery caught longjaw ciscoes and sold them as "smoked herring

Herring

Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

". The commercial catch peaked around the 1930s when about one-third of the catch of ciscoes was this species.

No individuals have been reported in commercial fish catches since 1967, and in Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 the last individual was recorded from Georgian Bay

Georgian Bay

Georgian Bay is a large bay of Lake Huron, located entirely within Ontario, Canada...

in 1975.