The ciscoes (or ''ciscos'') are salmonid fish that differ from other members of the genus '' Coregonus'' in having upper and lower jaws of approximately equal length and high gill raker counts. These species have been the focus of much study recently, as researchers have sought to determine the relationships among species that appear to have evolved very recently. ''Cisco'' is also specifically used for the North American species ''

Coregonus artedi ''Coregonus artedi'', commonly known as the cisco, is a North American species of freshwater whitefish in the family (biology), family Salmonidae. The number of species and definition of species limits in North American cisco (fish), ciscoes is a ...

'', also known as lake herring. In previous taxonomic classifications, the ciscoes have been identified as a subgenus ''Leucichthys'' of the genus '' Coregonus''. Based on molecular data this is not a natural classification however, as the ciscoes are

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

, comprising two different lineages within the

freshwater whitefish The freshwater whitefish are fishes of the subfamily Coregoninae, which contains whitefishes (both freshwater and anadromous) and ciscoes, and is one of three subfamilies in the salmon family Salmonidae. Apart from the subfamily Coregoninae, ...

es.Bernatchez L, Colombani F, Dodson JJ (1991
Phylogenetic relationships among the subfamily Coregoninae as revealed by mitochondrial DNA restriction analysis
''Journal of Fish Biology 39 (Suppl A):283-290.

Continental North American ciscoes: ''Coregonus artedi'' sensu lato

Eight taxa of cisco have been recognized in the Laurentian

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

and other interior lakes of the once-glaciated North America.Scott, W.B., Crossman, E.J. (1973) Freshwater Fishes of Canada. ''Bull. Fish. Res. B. Canada'' 184, 1–1092 * † Longjaw cisco – ''Coregonus alpenae'' *

Cisco Cisco Systems, Inc. (using the trademark Cisco) is an American multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, s ...

(lake cisco, northern cisco, or lake herring) – ''Coregonus artedi'' * † Deepwater cisco – ''Coregonus johannae'' * Bloater – ''Coregonus hoyi'' * Kiyi – ''Coregonus kiyi'' * † Blackfin cisco – ''Coregonus nigripinnis'' * Shortnose cisco – ''Coregonus reighardi'' (thought to be possibly extinct, rediscovered) * Shortjaw cisco – ''Coregonus zenithicus'' Usually, several taxa of ciscoes are found in a single lake. They exhibit different habitat distributions, feeding and breeding habits and morphological adaptations e.g. in their gill raker numbers. In the Great Lakes, at least five ciscoes coexist. According to genetic analyses, these cisco types do not represent unique, separate evolutionary lineages, but similar cisco morphs have evolved and attained their specific characteristics largely independently in each lake. Therefore, it has been suggested that they should not be recognized formally as distinct taxa, but all considered members of a single species, ''Coregonus artedi'' (

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

). or ''Coregonus artedi'' complex. Nevertheless, for conservation and management purposes the sympatric morphs in each lake should be considered ESUs, evolutionarily significant units. This taxonomic view is not widely accepted however, which has complicated discussions of the conservation status of some species. Ciscoes have been exploited in commercial fisheries, particularly in the Laurentian Great Lakes where the deepwater forms were the basis of the so-called chub fishery. The chub fishery had nothing to do with the various

cyprinid Cyprinidae is a Family (biology), family of freshwater fish commonly called the carp or minnow family, including the carps, the true minnows, and their relatives the barb (fish), barbs and barbel (fish), barbels, among others. Cyprinidae is the ...

fish species known as chubs but was exclusively based on the various species of ciscoes. The fishery continued as cisco stocks fell and non-native species such as sea lamprey,

rainbow smelt The rainbow smelt (''Osmerus mordax'') is a North American species of fish of the family (biology), family Osmeridae. Walleye, trout, and other larger fish prey on these smelt. The rainbow smelt prefer juvenile cisco (fish), ciscoes, zooplankton ...

and alewife spread through the system and increased in abundance. Alewife, in particular, have been implicated as a predator of cisco eggs and larvae, and as a competitor with ciscoes. The fishery shifted focus from species to species as cisco numbers declined and has been largely defunct for some years.

Ciscoes of northwestern North America

Three species of cisco inhabit waters of the northwestern North America. These have been found to represent distinct evolutionary lineages, by genetic data.Turgeon, J. & Bernatchez, L. (2003
Reticulate evolution and phenotypic diversity in North American ciscoes, ''Coregonus'' ssp. (Teleostei: Salmonidae): implications for the conservation of an evolutionary legacy
''

Conservation Genetics Conservation genetics is an interdisciplinary subfield of population genetics that aims to understand the dynamics of genes in a population for the purpose of natural resource management, conservation of genetic diversity, and the prevention of ...

'' 4: 67–81 *

Arctic cisco The Arctic cisco (''Coregonus autumnalis''), also known as Arctic omul (), is an anadromy, anadromous species of freshwater whitefish that inhabits the Arctic parts of Siberia especially Yenisey Gulf. It can also be found in Alaska and Canada. I ...

– ''Coregonus autumnalis'' * Bering cisco – ''Coregonus laurettae'' * Least cisco – ''Coregonus sardinella''

Eurasian ciscoes

The ranges of the three cisco species above extend across

Beringia Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 70th parallel north, 72° north latitude in the Chukchi Sea; and on the south ...

to the Asian coasts. Of those the Arctic cisco and least cisco (= sardine cisco) are widespread through northern

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

. In the inland waters of northern Europe, the European cisco or vendace (''Coregonus albula'') replaces the Siberian sardine cisco. Some of the cisco lineages are genetically very close, such as the European and sardine ciscoes. Within some species, geographically separated populations have been treated as distinct taxa, despite close genetic relationships, such as the vendace and the pollan (Arctic cisco) on the British Isles. The European cisco has also evolved into ecologically distinct

sympatric In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

populations or ecomorphs independently within several lakes (e.g. autumn and spring spawning populations, normal and dwarf morphs), which have been designated as distinct taxa, making the systematics complicated as with the North American ''

'' complex. * Bering cisco – ''Coregonus laurettae'' *

– ''Coregonus autumnalis'' ** Irish pollan - "''Coregonus pollan''": an Irish subspecies or group of populations * Sardine cisco (= least cisco) – ''Coregonus sardinella'' * Peled – ''Coregonus peled'': part of the ''C. sardinella'' complexPolitov DV, Bickham JW, Patton JC (2004
Molecular phylogeography of Palearctic and Nearctic ciscoes
''Ann. Zool. Fennici'' 41:13-23. * European cisco (=vendace) – ''Coregonus albula'' ** "'' Coregonus vandesius''": group of British populations ** Stechlin cisco – ''Coregonus fontanae'': local sympatric spring spawning dwarfed sister species ** '' Coregonus trybomi'': local sympatric spring-spawning sister species ** '' Coregonus lucinensis'': local sympatric dwarfed sister species

Phylogeny

Based on molecular data from

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

, the ciscoes comprise two distinct, unrelated groups: * The ''Coregonus artedi'' complex along with '' C. laurettae'' and '' C. autumnalis'' lineages * The ''Coregonus sardinella'' complex, including ''C. peled'' and ''C. albula''. This group is more closely related to the "true whitefishes" (e.g. the common whitefish ''C. lavaretus'', lake whitefish ''C. clupeaformis'') than to the ''C. artedi'' complex ciscoes.

References

* {{Reflist Freshwater fish of the Arctic Fish of the Great Lakes Coregonus Fish common names