Shortjaw cisco
Encyclopedia
The shortjaw cisco is a deepwater cisco
or chub (not to be confused with various species of Cyprinidae called chubs). 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. It typically weighs approximately 300 g (11 oz), and ranges from 150 to greater than 300 mm (6 to 12 inches) standard length
. Very difficult to differentiate from other cisco species by superficial appearance, this species typically has fewer gillrakers
than other ciscoes.
Once common throughout the upper Laurentian Great Lakes it is no longer found in Lake Michigan
and populations are much lower in Lake Huron
than in the past. The population in Lake Superior
is known to be lower than historically, based on commercial catch statistics. Its status in Lake Nipigon
is uncertain. It has been reported in at least 22 other lakes outside of the Great Lakes, from the Canadian provinces of Ontario
, Manitoba
, Saskatchewan
, Alberta
, and the Northwest Territories
. It is not known whether the remaining Great Lakes populations are increasing, decreasing or stable. Population trends in other lakes are unknown.
The shortjaw cisco is most commonly found in the deeper waters of large lakes. It has been found at depths of between 55 to 114 m (180 to 375 feet) in lakes Superior, Michigan, and Huron, and is known to exhibit seasonal changes in depth distribution in Lake Superior.
Spawning occurs in the autumn. Eggs are deposited over the lake bottom in deep water and develop over three to four months, depending on water temperature. This fish reaches sexual maturity at five years of age.
Crustaceans and insect larvae are important food items. Lake trout
(Salvelinus namaycush) and burbot
(Lota lota) are known to feed on shortjaw cisco. Shortjaw cisco are believed to be vulnerable to the invasive sea lamprey
(Petromyzon marinus,) which has presumably played a role in its decline in the Great Lakes, where expansion in the range of sea lamprey has overlapped the decline in shortjaw cisco numbers.
This species was an important component of the chub fishery in the Great Lakes. Competition and predation from rainbow smelt
(Osmerus mordax)and alewife
(Alosa pseudoharengus), two introduced exotic fish species, have had a negative impact on shortjaw cisco populations. The cumulative effect of these factors, sea lamprey predation and habitat changes associated with urban, agricultural, and industrial activities in the Great Lakes Basin
undoubtedly combined to make this species vulnerable to over-exploitation, even at exploitation rates that had once been sustainable.
The systematics of the group of fishes called "ciscoes
" is complicated and some scientists propose that the species we now call shortjaw cisco is one form of a species that would include longjaw cisco
(Coregonus alpenae), previously considered a distinct species. Longjaw cisco are presumed extinct.
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 (not to be confused with various species of Cyprinidae called chubs). 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. It typically weighs approximately 300 g (11 oz), and ranges from 150 to greater than 300 mm (6 to 12 inches) standard length
Ichthyology terms
Ichthyology uses several terms that are unique to the science.Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z- A :* Abdomen: belly* Abdominal: pertaining to the belly* Actinosts: a series of bones at the base of the pectoral rays....
. Very difficult to differentiate from other cisco species by superficial appearance, this species typically has fewer gillrakers
Ichthyology terms
Ichthyology uses several terms that are unique to the science.Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z- A :* Abdomen: belly* Abdominal: pertaining to the belly* Actinosts: a series of bones at the base of the pectoral rays....
than other ciscoes.
Once common throughout the upper Laurentian Great Lakes it is no longer found in Lake 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 populations are much lower in Lake 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...
than in the past. The population in Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
is known to be lower than historically, based on commercial catch statistics. Its status in Lake Nipigon
Lake Nipigon
Lake Nipigon is the largest lake entirely within the boundaries of the Canadian province of Ontario . It is sometimes described as the sixth Great Lake. Lying 260 metres above sea level, the lake drains into the Nipigon River and thence into Nipigon Bay of Lake Superior...
is uncertain. It has been reported in at least 22 other lakes outside of the Great Lakes, from the Canadian provinces of 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....
, Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...
, Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, and the Northwest Territories
Northwest Territories
The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...
. It is not known whether the remaining Great Lakes populations are increasing, decreasing or stable. Population trends in other lakes are unknown.
The shortjaw cisco is most commonly found in the deeper waters of large lakes. It has been found at depths of between 55 to 114 m (180 to 375 feet) in lakes Superior, Michigan, and Huron, and is known to exhibit seasonal changes in depth distribution in Lake Superior.
Spawning occurs in the autumn. Eggs are deposited over the lake bottom in deep water and develop over three to four months, depending on water temperature. This fish reaches sexual maturity at five years of age.
Crustaceans and insect larvae are important food items. Lake trout
Lake trout
Lake trout is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, lake char , touladi, togue, and grey trout. In Lake Superior, they can also be variously known as siscowet, paperbellies and leans...
(Salvelinus namaycush) and burbot
Burbot
The burbot is the only gadiform fish inhabiting freshwaters. It is also known as mariah, the lawyer, and eelpout. It is closely related to the marine common ling and the cusk...
(Lota lota) are known to feed on shortjaw cisco. Shortjaw cisco are believed to be vulnerable to the invasive 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...
(Petromyzon marinus,) which has presumably played a role in its decline in the Great Lakes, where expansion in the range of sea lamprey has overlapped the decline in shortjaw cisco numbers.
This species was an important component of the chub fishery in the Great Lakes. Competition and predation from rainbow smelt
Rainbow smelt
The rainbow smelt, Osmerus mordax, is an anadromous species of fish of the family Osmeridae. The distribution of Osmerus mordax is circumpolar. The rainbow smelt was introduced to the Great Lakes, and from there has made its way to various other places. Walleye, trout, and other larger fish prey on...
(Osmerus mordax)and alewife
Alewife
The alewife is a species of herring. There are anadromous and landlocked forms. The landlocked form is also called a sawbelly or mooneye...
(Alosa pseudoharengus), two introduced exotic fish species, have had a negative impact on shortjaw cisco populations. The cumulative effect of these factors, sea lamprey predation and habitat changes associated with urban, agricultural, and industrial activities in the Great Lakes Basin
Great Lakes Basin
The Great Lakes Basin consists of the Great Lakes and the surrounding lands of the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin in the United States, and the province of Ontario in Canada, whose direct surface runoff and watersheds form a large...
undoubtedly combined to make this species vulnerable to over-exploitation, even at exploitation rates that had once been sustainable.
The systematics of the group of fishes called "ciscoes
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...
" is complicated and some scientists propose that the species we now call shortjaw cisco is one form of a species that would include longjaw cisco
Longjaw cisco
The longjaw cisco was a deep water cisco or chub, usually caught at depths of 100 metres or more from Lakes Huron, Michigan, and Erie. Its Latin name was derived from Alpena, a city in Michigan...
(Coregonus alpenae), previously considered a distinct species. Longjaw cisco are presumed extinct.