Eelpout

{{Short description|Family of fishes}} {{About|the family of marine fish|the freshwater fish species known as eelpout in some regions of North America|burbot}} {{Automatic taxobox | image = Halfbarred Pout Gymnelus hemifasciatus FemaleTypeA.jpg | image_caption = ''Gymnelus hemifasciatus'' | taxon = Zoarcidae | authority = Swainson, 1839<ref name = VDLEF>{{cite journal | author1 = Richard van der Laan | author2 = William N. Eschmeyer | author3 = Ronald Fricke | name-list-style = amp | year = 2014 | title = Family-group names of Recent fishes | url = https://www.researchgate.net/publication/268078514 | journal = Zootaxa | volume = 3882 | issue = 2 | pages = 001–230 | doi = 10.11646/zootaxa.3882.1.1 | pmid = 25543675 | doi-access = free }}</ref><ref name="Swainson, 1838"/> | subdivision_ranks = Subfamilies | subdivision = See text }}

The '''eelpouts''' are the ray-finned fish family '''Zoarcidae'''. As the common name suggests, they are somewhat eel-like in appearance. All of the 300 species are marine and mostly bottom-dwelling, some at great depths. Eelpouts are predominantly found in the Northern Hemisphere. The Arctic, north Pacific and north Atlantic oceans have the highest concentration of species; however, species are found around the globe.

They are conventionally placed in the "perciform" assemblage; in fact, the Zoarcoidei seem to be specialized members of the Gasterosteiformes-Scorpaeniformes group of Acanthopterygii.<ref name=kawa>{{cite journal | author = Kawahara, R. | author2 = Miya, M. | author3 = Mabuchi, K. | author4 = Lavoué, S. | author5 = Inoue, J.G. | author6 = Satoh, T.P. | author7 = Kawaguchi, A. | author8 = Nishida, M. | name-list-style=amp| year = 2008 | title = Interrelationships of the 11 gasterosteiform families (sticklebacks, pipefishes, and their relatives): a new perspective based on whole mitogenome sequences from 75 higher teleosts | journal = Molecular Phylogenetics and Evolution | volume = 46 | issue = 1| pages = 224–36 | doi=10.1016/j.ympev.2007.07.009 | pmid=17709262}}</ref>

The largest member of the family is ''Zoarces americanus'', which may reach {{Convert|1.1|m|abbr=on}} in length. Other notable genera include ''Lycodapus'' and ''Gymnelus''.

==Taxonomy== The eelpout family was first proposed as the family Zoarchidae in 1839 by the English naturalist William Swainson but the spelling was changed to Zoarcidae after the spelling of the genus Zoarces was corrected by Theodore Gill in 1861.<ref name = VDLEF/> The 5th edition of ''Fishes of the World'' classifies this family within the suborder Zoarcoidei, within the order Scorpaeniformes.<ref name = Nelson5>{{cite book |title=Fishes of the World |edition=5th |author1=J. S. Nelson |author2=T. C. Grande |author3=M. V. H. Wilson |year=2016 |pages=478–482 |publisher=Wiley |isbn=978-1-118-34233-6 |url=https://sites.google.com/site/fotw5th/ |access-date=2022-10-05 |archive-date=2019-04-08 |archive-url=https://web.archive.org/web/20190408194051/https://sites.google.com/site/fotw5th/ |url-status=dead }}</ref> Other authorities classify this family in the infraorder Zoarcales within the suborder Cottoidei of the Perciformes because removing the Scorpaeniformes from the Perciformes renders that taxon non monophyletic.<ref name = Deepfin>{{cite journal | author1 = Ricardo Betancur-R | author2 = Edward O. Wiley | author3 = Gloria Arratia | author4 = Arturo Acero | author5 = Nicolas Bailly | author6 = Masaki Miya | author7 = Guillaume Lecointre | author8 = Guillermo Ortí | display-authors = 3 | title =Phylogenetic classification of bony fishes | journal = BMC Evolutionary Biology | volume = 17 | issue = 162 | year = 2017 | page = 162 | doi = 10.1186/s12862-017-0958-3 | pmid = 28683774 | pmc = 5501477 | doi-access = free }}</ref>

''Fishes of the World'' mentions four subfamilies but does not assign genera to the subfamilies<ref name = Nelson5/> but these were set out in Anderson and Federov's Annotated Checklist<ref name = A&F2004>{{cite journal | author1 = Anderson , M. E. | author2 = V. V . Fedorov | name-list-style = and | year = 2004 | title = Family Zoarcidae Swainson 1839 — eelpouts | journal = California Academy of Sciences Annotated Checklists of Fishes | volume = 34 | url = https://www.calacademy.org/sites/default/files/assets/docs/zoarcidae.pdf}}</ref> and this has been followed by ''FishBase''<ref name = Fishbase>{{FishBase family|family=Zoarcidae| month=June|year=2022}}</ref> and ''Catalog of Fishes''.<ref name = CofF/>

== Evolution and adaptations == Eelpouts lay demersal eggs, which are eggs that are deposited on the seafloor, and can be either free or connected to the substrate. These egg clusters can range from 9.2 mm, to 9.8 mm, which are the largest compared to any other marine egg cluster.<ref name=":1">{{Citation |title=INDEX |date=1990 |work=Cognitive Ergonomics |pages=257–261 |url=http://dx.doi.org/10.1016/b978-0-12-248290-8.50022-4 |access-date=2024-04-10 |publisher=Elsevier|doi=10.1016/b978-0-12-248290-8.50022-4 |isbn=978-0-12-248290-8 |url-access=subscription }}</ref> It has been found that eelpouts grow larger and heavier in areas where the water is relatively shallow. In these areas, this species consumes molluscs, invertebrates, and small fish. The difference of biodiversity at varying depths has led to the evolution of distinct populations, connecting to the study that temperature might have a significant effect on them.<ref name=":2">{{Cite book |last=Publishers |first=Estonian Academy |url=https://books.google.com/books?id=1IcwnNcGB0oC&dq=microevolution+of+eelpout&pg=PA292 |title=Proceedings of the Estonian Academy of Sciences, Biology and Ecology |date=2016 |publisher=Estonian Academy Publishers |language=en}}</ref> Studies have shown that there are three large families of eelpout species; Zoarcidae, Stichaeidae, and Pholidae. These species have been thought to have evolved in northern, colder seas, each diverging off of each other at different points in time, millions of years ago.<ref name=":3">{{Cite journal |last=Radchenko |first=O. A. |date=2016 |title=Timeline of the evolution of eelpouts from the suborder Zoarcoidei (Perciformes) based on DNA variability |url=http://link.springer.com/10.1134/S0032945216040123 |journal=Journal of Ichthyology |language=en |volume=56 |issue=4 |pages=556–568 |doi=10.1134/S0032945216040123 |issn=0032-9452|url-access=subscription }}</ref> The notched-fin eelpout, which is commonly found in the Sea of Okhotsk, have shown researchers what the average length of an adult eelpout is, usually sitting between 21 and 26 cm long (females typically larger than males).<ref name=":4">{{Cite journal |last1=Il’insky |first1=E. N. |last2=Kuznetsova |first2=N. A. |date=July 2010 |title=Spatial and length distribution, sex composition, and feeding of the notched-fin eelpout Zoarces elongatus (Perciformes: Zoarcidae) in the Sea of Okhotsk |url=http://link.springer.com/10.1134/S1063074010040036 |journal=Russian Journal of Marine Biology |language=en |volume=36 |issue=4 |pages=252–257 |doi=10.1134/S1063074010040036 |issn=1063-0740|url-access=subscription }}</ref> Their size has been found to increase as the depth of water in which they have been studied lowers. They feed commonly on Gammarids (small, shrimp like organisms), Polychaetes (marine worms), and Bivalves (clams and muscles) on the seafloor.<ref name=":4" />

==Subfamilies and genera== The eelpouts are classified into four subfamilies and 61 genera with around 300 species:<ref name = CofF>{{Cof family| family = Zoarcidae|access-date = 4 October 2022}}</ref><ref name = VDLEF/> [[Image:Bothrocara brunneum.jpg|thumb|right|''Bothrocara brunneum'']] thumb|right|''Lycodes turneri'' thumb|right|''Pachycara sp.'' thumb|right|''Zoarces viviparus'' {{div col|colwidth=28em}} * subfamily Gymnelinae Gill, 1863 ** ''Andriashevia'' Fedorov & Neelov, 1978 ** ''Barbapellis'' Iglésias, Dettai & Ozouf-Costaz, 2012 ** ''Bilabria'' Schmidt, 1936 ** ''Davidijordania'' Popov, 1931 ** ''Ericandersonia'' Shinohara & Sakurai, 2006 ** ''Gymnelopsis'' Soldatov, 1922 ** ''Gymnelus'' Reinhardt 1834 ** ''Hadropareia'' Schmidt, 1904 ** ''Krusensterniella'' Schmidt, 1904 ** ''Magadanichthys'' Shinohara, Nazarkin & Chereshnev, 2006 ** ''Melanostigma'' Günther, 1881 ** ''Nalbantichthys'' Schultz, 1967 ** ''Opaeophacus'' Bond & Stein, 1984 ** ''Puzanovia'' Fedorov, 1975 ** ''Seleniolycus'' Anderson, 1988 * subfamily Lycodinae Gill, 1861 ** ''Aiakas'' Gosztonyi, 1977 ** ''Argentinolycus'' Matallanas & Corbella, 2012 ** ''Austrolycus'' Regan, 1913 ** ''Bellingshausenia'' Matallanas, 2009 ** ''Bentartia'' Matallanas, 2010 ** ''Bothrocara'' Bean, 1890 ** ''Bothrocarina'' Suvorov, 1935 ** ''Crossostomus'' Lahille, 1908 ** ''Dadyanos'' Whitley, 1951 ** ''Derepodichthys'' Gilbert, 1896 ** ''Dieidolycus'' Anderson, 1988 ** ''Eucryphycus'' Anderson, 1988 ** ''Exechodontes'' DeWitt, 1977 ** ''Gosztonyia'' Matallanas, 2009 ** ''Hadropogonichthys'' Fedorov, 1982 ** ''Iluocoetes'' Jenyns, 1842 ** ''Japonolycodes'' Shinohara, Sakurai & Machida, 2002 ** ''Letholycus'' Anderson, 1988 ** ''Lycenchelys'' Gill, 1884 ** ''Lycodapus'' Gilbert, 1890 ** ''Lycodes'' Reinhardt, 1831 ** ''Lycodichthys'' Pappenheim, 1911 ** ''Lycodonus'' Goode & Bean, 1883 ** ''Lycogrammoides'' Soldatov & Lindberg, 1928 ** ''Lyconema'' Gilbert, 1896 ** ''Maynea'' Cunningham, 1871 ** ''Notolycodes'' Gosztonyi, 1977 ** ''Oidiphorus'' McAllister & Rees 1964 ** ''Ophthalmolycus'' Regan, 1913 ** ''Pachycara'' Zugmayer. 1911 ** ''Patagolycus'' Matallanas & Corbella, 2012 ** ''Petroschmidtia'' Taranetz & Andriashev, 1934 ** ''Phucocoetes'' Jenyns, 1842 ** ''Piedrabuenia'' Gosztonyi, 1977 ** ''Plesienchelys'' Anderson, 1988 ** ''Pogonolycus'' Norman, 1937 ** ''Pyrolycus'' Machida & Hashimoto, 2002 ** ''Santelmoa'' Matallanas, 2010 ** ''Taranetzella'' Andriashev, 1952 ** ''Thermarces'' Rosenblatt & Cohen, 1986 ** ''Zestichthys'' Jordan & Hubbs, 1925 * subfamily Lycozarcinae Andriashev, 1939 ** ''Lycozoarces'' Popov, 1935 * subfamily Zoarcinae Swainson, 1839 ** ''Zoarces'' Cuvier 1829 {{div col end}}

==Characteristics== The body of eelpouts is relatively elongated and laterally compressed.<ref name=":00">{{Cite journal |pages=89–96 [https://www.biodiversitylibrary.org/page/15775757#page/103/mode/1up p. 91] |last=Anderson |first=M. Eric |date=1988-02-05 |url=https://www.biodiversitylibrary.org/page/15775757#page/101/mode/1up |title=''Eucryphycus'', a new genus of California eelpout (Teleostei: Zoarcidae) based on ''Maynea californica'' Starks and Mann, 1911 |journal= Proceedings of the California Academy of Sciences |series=4th |volume=45 |issue=5}}</ref> Their heads are relatively small and ovoid. Juveniles have a more rounded snout and relatively larger eye than adults.<ref name=":00"/> Their scales are absent or very small.<ref name="Burke Fish Key">{{cite web |title=Family Zoarcidae: Eelpouts |url=https://www.burkemuseum.org/static/FishKey/zoarc.html |website=Key to Fishes of the Puget Sound |publisher=Burke Museum |access-date=10 September 2022}}</ref> The dorsal and anal fins are continuous down their bodies up to their caudal fin. They produce the pigment biliverdin, which turns their bones green. This feature has no apparent evolutionary function and is harmless.<ref name=":01">{{Cite web |url=https://www.fishbase.se/summary/479|title = Zoarces viviparus (Linnaeus, 1758), Eelpout |editor1=Froese, R. |editor2=D. Pauly |website=FishBase}}</ref> Overall, there is no sexual dimorphism.<ref>{{Cite journal |url=https://www.biodiversitylibrary.org/page/19238475#page/233/mode/1up |journal=Proceedings of the California Academy of Sciences |series=4th |last=Anderson |first=M. Eric |date=1989-12-20 |title=Review of the eelpout genus ''Pachycara'' Zugmayer, 1911 (Teleostei: Zoarcidae), with descriptions of six new species |volume=46 |issue=10 |pages=221–242}}</ref>

===Biology=== Little is known about eelpout populations because they often slip through nets in sampling studies, and because some species live in inaccessibly deep habitats. Species for which trophic ecology has been documented are typically, if not always, benthic scavengers or predators.<ref name=":01"/><ref>{{cite journal |title=Aquarium Observations on Feeding by Melanostigma pammelas (Pisces: Zoarcidae) |journal=Copeia |date=May 18, 1979 |doi=10.2307/1443432 |jstor=1443432 |last1=Belman |first1=Bruce W. |last2=Anderson |first2=M. Eric |volume=1979 |issue=2 |pages=366–369 }}</ref> At least one species has also adapted the ability to breathe air when out of water.<ref name=":01"/>

==Timeline==

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==References== {{Reflist|refs= <ref name="Swainson, 1838">{{cite book|last1=Swainson|first1=William|title=On the Natural History and Classification of Fishes, Amphibians, and Reptiles|date=1839|publisher=Longman, Orme, Brown, Greene, & Longmans|location=London|volume=2|pages=82–83, 184, 283|doi=10.5962/bhl.title.62140|doi-access=free}}</ref> }}

Category:Zoarcidae

Eelpout

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