The ciscoes (or ciscos) 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. 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. The term cisco is also specifically used of the North American species Coregonus artedi, 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, but the ciscoes are polyphyletic, comprising two different lineages within the freshwater whitefishes.^[1]

Continental North American ciscoes: Coregonus artedi sensu lato

Eight taxa of cisco have been recognized in the Laurentian Great Lakes and other interior lakes of the once-glaciated North America.^[2]

• Longjaw cisco – Coregonus alpenae
• Cisco (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
• 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.^[3]

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).^[3] or Coregonus artedi complex. Nevertheless for conservation and management purposes the sympatric morphs in each lake should be considered ESUs, evolutionarily significant units.^[3] This taxonomic view is not widely accepted however, which has complicated discussions of the conservation status of some species.^[4]

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 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 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.

Bering cisco

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.^[3]

• Arctic cisco – Coregonus autumnalis
• Bering cisco – Coregonus laurettae
• Least cisco – Coregonus sardinella

Eurasian ciscoes

The ranges of the three cisco species above extend across Beringia to the Asian coasts. Of those the Arctic cisco and least cisco (=sardine cisco) are widespread through northern Siberia. 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 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 Coregonus artedi complex.

• Bering cisco – Coregonus laurettae
• Arctic cisco – 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 complex^[5]
• 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, the ciscoes comprise two distinct, unrelated groups:^[1]

• 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

• Froese, Rainer, and Daniel Pauly, eds. (2004). Species of Coregonus in FishBase. October 2004 version.

Coregonus is a diverse genus of fish in the salmon family (Salmonidae). The type species is Coregonus lavaretus. The Coregonus species are known as whitefishes. The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate.

Several species, including the Arctic cisco (C. autumnalis), the Bering cisco (C. laurettae), and the least cisco (C. sardinella) are anadromous, moving between salt water and fresh water.

The genus was previously subdivided into two subgenera Coregonus ("true whitefishes") and Leucichthys ("ciscoes"), Coregonus comprising taxa with sub-terminal mouth and usually a benthic feeding habit, Leucichthys those with terminal or supra-terminal mouth and usually a pelagic plankton-feeding habit. This classification is not natural however: based on molecular data, ciscoes comprise two distinct lineages within the genus. Moreover, the genus Stenodus is not phylogenetically distinct from Coregonus.^[1]

Many whitefish species or ecotypes, especially from the Great Lakes and the Alpine lakes of Europe, have gone extinct over the past century or are endangered. All Coregonus species are protected under appendix III of the Bern Convention.

Species

There is much uncertainty and confusion in the classification of the many of species of this genus. There are currently 78 extant and recently extinct species in this genus recognised by FishBase as of February 2012 (extinct species are marked with a dagger, "†"):^[2]

• Coregonus albellus Fatio, 1890 (autumn brienzlig)
• Coregonus albula (Linnaeus, 1758) (vendace)
• †Coregonus alpenae (Koelz, 1924) (longjaw cisco)
• Coregonus alpinus Fatio, 1885 (kropfer)
• Coregonus anaulorum Chereshnev, 1996
• Coregonus arenicolus Kottelat, 1997
• Coregonus artedi Lesueur, 1818 (northern cisco or lake herring)

Cisco or lake herring, Coregonus artedi

• Coregonus atterensis Kottelat, 1997
• Coregonus austriacus C. C. Vogt, 1909
• Coregonus autumnalis (Pallas, 1776) (Arctic cisco)
• Coregonus baerii Kessler, 1864
• Coregonus baicalensis Dybowski, 1874
• Coregonus baunti Mukhomediyarov, 1948
• Coregonus bavaricus Hofer, 1909
• Coregonus bezola Fatio, 1888 (bezoule)
• Coregonus candidus Goll, 1883
• Coregonus chadary Dybowski, 1869 (Khadary whitefish)
• Coregonus clupeaformis (Mitchill, 1818) (lake whitefish)
• Coregonus clupeoides Lacépède, 1803 (powan)
• Coregonus confusus Fatio, 1885
• Coregonus danneri C. C. Vogt, 1908
• Coregonus duplex Fatio, 1890
• Coregonus fatioi Kottelat, 1997
• †Coregonus fera Jurine, 1825 (fera)
• Coregonus fontanae M. Schulz & Freyhof, 2003 (Stechlin cisco)
• †Coregonus gutturosus (C. C. Gmelin, 1818)
• Coregonus heglingus Schinz, 1822
• †Coregonus hiemalis Jurine, 1825 (gravenche)
• Coregonus hoferi L. S. Berg, 1932
• Coregonus holsata Thienemann, 1916

Bloater, Coregonus hoyi

• Coregonus hoyi (Milner, 1874) (bloater)
• Coregonus huntsmani W. B. Scott, 1987 (Atlantic whitefish)
• †Coregonus johannae (G. Wagner, 1910) (deepwater cisco)
• Coregonus kiletz Michailovsky, 1903
• Coregonus kiyi (Koelz, 1921) (kiyi)
• Coregonus ladogae Pravdin, Golubev & Belyaeva, 1938
• Coregonus laurettae T. H. Bean, 1881 (Bering cisco)

Common whitefish, Coregonus lavaretus (sensu lato)

• Coregonus lavaretus (Linnaeus, 1758) (common whitefish, European whitefish; lavaret)
• Coregonus lucinensis Thienemann, 1933
• Coregonus lutokka Kottelat, Bogutskaya & Freyhof, 2005
• Coregonus macrophthalmus Nüsslin, 1882
• Coregonus maraena (Bloch, 1779) (maraena whitefish)
• Coregonus maraenoides L. S. Berg, 1916
• Coregonus maxillaris Günther, 1866
• Coregonus megalops Widegren, 1863 (lacustrine fluvial whitefish)
• Coregonus migratorius (Georgi, 1775) (omul)
• Coregonus muksun (Pallas, 1814) (muksun)
• Coregonus nasus (Pallas, 1776) (broad whitefish)

Coregonus nelsonii

• Coregonus nelsonii T. H. Bean, 1884 (Alaska whitefish)
• Coregonus nigripinnis (Milner, 1874) (blackfin cisco)
• Coregonus nilssoni Valenciennes, 1848
• Coregonus nipigon (Koelz, 1925)
• Coregonus nobilis Haack, 1882
• †Coregonus oxyrinchus (Linnaeus, 1758) (houting)
• Coregonus palaea G. Cuvier, 1829
• Coregonus pallasii Valenciennes, 1848
• Coregonus peled (J. F. Gmelin, 1789) (peled)
• Coregonus pennantii Valenciennes, 1848 (gwyniad)

Coregonus pidschian

• Coregonus pidschian (J. F. Gmelin, 1789) (humpback whitefish)
• Coregonus pollan W. Thompson, 1835 (Irish pollan)
• Coregonus pravdinellus Dulkeit, 1949
• Coregonus reighardi (Koelz, 1924) (shortnose cisco)
• Coregonus renke (Schrank, 1783)
• Coregonus restrictus Fatio, 1885
• Coregonus sardinella Valenciennes, 1848 (Sardine cisco)
• Coregonus stigmaticus Regan, 1908 (schelly)
• Coregonus subautumnalis Kaganowsky, 1932
• Coregonus suidteri Fatio, 1885
• Coregonus trybomi Svärdson, 1979
• Coregonus tugun (Pallas, 1814)
• Coregonus ussuriensis L. S. Berg, 1906 (Amur whitefish)
• Coregonus vandesius J. Richardson, 1836 (vendace)
• Coregonus vessicus Dryagin, 1932
• Coregonus wartmanni (Bloch, 1784)
• Coregonus widegreni Malmgren, 1863 (Valaam whitefish)
• Coregonus zenithicus (D. S. Jordan & Evermann, 1909) (shortjaw cisco)
• Coregonus zuerichensis Nüsslin, 1882
• Coregonus zugensis Nüsslin, 1882

References

• "Coregonus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=161932. Retrieved 12 December 2004. 
• Division of Endangered Species, U.S. Fish and Wildlife Service. "Extinct Species List". U.S. Fish and Wildlife Service. http://midwest.fws.gov/endangered/lists/extinct.html. Retrieved 12 December 2004.