{{Short description|Genus of fishes}} {{Automatic Taxobox | image=Comephorus_baikalensis.jpg | image2=Golomjanka.png | parent_authority = Günther, 1861 | taxon = Comephorus | authority = Lacepède, 1800 | display_parents = 2 | subdivision_ranks = Species | type_species = ''Comephorus baikalensis'' | type_species_authority = Pallas, 1776<ref name = CofF>{{Cof family|family=Cottidae|access-date=4 March 2023}}</ref> }}
'''''Comephorus''''', known as the '''golomyankas''' or '''Baikal oilfish''', are a genus comprising two species of peculiar sculpin fishes endemic to Lake Baikal in Russia. ''Comephorus'' is the only genus in the subfamily '''Comephorinae'''. Golomyankas are pelagic fishes and the main food source for the Baikal seal.
==Taxonomy== ''Comephorus'' was first proposed as a monospecific genus in 1800 by the French naturalist and politician Bernard Germain de Lacépède with ''Callionymus baikalensis'' as its only species.<ref name = CofF/> The 5th edition of ''Fishes of the World'' places this genus in the monotypic subfamily Comephorinae within the family Cottidae, the typical sculpins.<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=467–495 |publisher=Wiley |isbn=978-1-118-34233-6 |url=https://sites.google.com/site/fotw5th/ |access-date=2023-03-04 |archive-date=2022-06-01 |archive-url=https://web.archive.org/web/20220601121150/https://sites.google.com/site/fotw5th/ }}</ref> Other authorities have used phylogenetic studies which have found that Baikal sculpins that were classified in the subfamilies Comephorinae and Abyssocottinae by ''Fishes of the World'' radiated from an ancestor which was likely to be within the genus ''Cottus'' and that the classification of the Baikal sculpins in a different taxon from ''Cottus'' was paraphyletic.<ref name = S&B2014>{{cite journal | author1 = W. Leo Smith | author2 = Morgan S. Busby | name-list-style = & | year = 2014 | title = Phylogeny and taxonomy of sculpins, sandfishes, and snailfishes (Perciformes: Cottoidei) with comments on the phylogenetic significance of their early-life-history specializations | journal = Molecular Phylogenetics and Evolution | volume = 79 | pages = 332–352 | doi = 10.1016/j.ympev.2014.06.028| pmid = 25014569 | bibcode = 2014MolPE..79..332S }}</ref>
==Description== ''Comephorus'' have translucent bodies with no scales,<ref name=irkutsk>[http://baikal.irkutsk.org/animals.htm Animals and plants of Lake Baikal] from Irkutsk State University, accessed May 5, 2006</ref> but appear dull when dead.<ref name=scfh>{{cite web| title=Mysterious Fish of Lake Baikal | url=https://scfh.ru/en/papers/mysterious-fish-of-lake-baikal/ | publisher=Science First Hand | volume=3, N2 | date=30 September 2004 | access-date=31 May 2017}}</ref> The big Baikal oilfish (''C. baikalensis'') can reach up to {{convert|21|cm|in|abbr=on}} in length and the little Baikal oilfish (''C. dybowskii'') up to {{convert|16|cm|in|abbr=on}}.<ref name=fishbase/> Males are smaller than females, only reaching about {{2/3}} the length.<ref name=Fishwatching2016b>{{cite web| title=ГОЛОМЯНКИ, ЧАСТЬ 2: ОСОБЕННОСТИ СТРОЕНИЯ | url=http://fishwatching.org/comephorus-anatomy/ | publisher=Fishwatching | language=Russian | date=29 January 2016 | access-date=5 March 2018}}</ref> They have long pectoral fins, and although pelvic bones are present, they lack pelvic fins. They have a strong lateral line. The lateral line system on the head consists of large cavities linked by narrow, bony bridges with small external pores. High lipid content and porous bones result in an almost neutral buoyancy<ref name=Sideleva>Sideleva, V.G. (1996). Comparative character of the deep-water and inshore cottoid fishes endemic to Lake Baikal. Journal of Fish Biology 49(sA): 192–206.</ref> and lack of swim bladder allows the fish to tolerate varying pressure extremes as they move through the water column. Over a third of the body weight (38.9%) of ''C. baikalensis'' is oil, but ''C. dybowskii'' contains far less (4.7%).<ref>{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0305049100002078 | doi=10.1016/S0305-0491(00)00207-8 | title=Lipids and fatty acids of two pelagic cottoid fishes (Comephorus spp.) endemic to Lake Baikal | journal=Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology | date=August 2000 | volume=126 | issue=4 | pages=477–485 | last1=Kozlova | first1=T. A. | last2=Khotimchenko | first2=S. V. | pmid=11026659 | url-access=subscription }}</ref> It has been said that they decompose in sunlight, leaving behind only fatty oil and bones,<ref name=bww/> although the accuracy of this claim has been questioned.<ref name=scfh/> Unusually, their eyes only contain rod cells (not cone cells), indicating a high sensitivity to light.<ref name=Fishwatching2016b/> Some of the adaptions in golomyankas resemble those seen in deep sea fish.<ref name=Sideleva/>
==Species== There are currently two recognized species in this genus:<ref name=fishbase>{{FishBase genus | genus = Comephorus| month = December | year = 2012}}</ref> * ''Comephorus baikalensis'' <small>(Pallas, 1776)</small> (big Baikal oilfish) * ''Comephorus dybowskii'' <small>Korotneff, 1904</small> (little Baikal oilfish)
==Biology and ecology== The common name ''golomyanka'' originates from the old-Russian ''golomen'', meaning "far from the shore" in the local dialect and referring to their pelagic behavior.<ref name=1baikalKTB>{{cite web| title=Baikal "shark": Amazing fact about the Baikal oilfish (golomyanka) | url=http://1baikal.ru/en/o-bajkale/mestnyie-remesla/baikal-"shark"-amazing-facts-about-baikal-oilfish-(golomyanka) |publisher=Key to Baikal | date=19 May 2017| access-date=31 May 2017}}</ref> They are the principal ecological competitor to the omul, which also eat small golomyankas, and represent a primary food source for the Baikal seal, at more than 90% of its diet.<ref name=scfh/> They are easily identifiable, and are large enough to be easily seen. Golomyankas are unusual for occurring pelagically throughout the entire water column of Lake Baikal, ranging from depths of around {{convert|1.6|km|mi|abbr=on|1}} to near the surface, but they primarily occur deeper than {{convert|100|m|ft|abbr=on}}.<ref>{{FishBase | genus = Comephorus | species = baikalensis | month = September | year = 2016}}</ref><ref name=fishbasedybowskii>{{FishBase | genus = Comephorus | species = dybowskii | month = September | year = 2016}}</ref> During the night they move up the water column to feed, often occurring as shallow as {{convert|10-25|m|ft|abbr=on}},<ref>{{cite iucn |author=Goodman, S. |date=2016 |title=''Pusa sibirica'' |volume=2016 |article-number=e.T41676A45231738 |doi=10.2305/IUCN.UK.2016-1.RLTS.T41676A45231738.en |access-date=13 November 2021}}</ref> and in the winter they can occasionally be seen swimming just below the ice-covered surface.<ref name=Fishwatching2016a>{{cite web| title=ГОЛОМЯНКИ, ЧАСТЬ 1: ЭКОЛОГИЯ ВИДОВ | url=http://fishwatching.org/comephorus-ecology/ | publisher=Fishwatching | language=Russian | date=21 January 2016 | access-date=5 March 2018}}</ref> They are considered the world's most abyssal freshwater fish, together with certain Lake Baikal deep-water sculpins (Abyssocottidae).<ref name=hunt>Hunt, D. M., et al. (1997). Molecular evolution of the cottoid fish endemic to Lake Baikal deduced from nuclear DNA evidence. ''Molecular Phylogenetics and Evolution'' 8(3), 415–22.</ref> They move without much regard for changes in pressure, although they can exist only in cold temperatures, preferring water that is no more than {{convert|5|C|F|abbr=on}} and dying at {{convert|10|C|F|abbr=on}}.<ref name=irkutsk/><ref name=bww>[http://www.bww.irk.ru/baikalfauna/baikalfauna.html Ichthyofauna of Lake Baikal] from Baikal Web World, accessed May 5, 2006 (with a photo of the golomyanka).</ref>
The biomass of the golomyanka population is estimated at about 150 thousand tons, making it the most populous fish in Lake Baikal.<ref name=irkutsk/><ref name=bww/> It is estimated that about 70% of the fish in the lake are golomyankas.<ref name=1baikalKTB/> Their juveniles are also the most abundant pelagic fish larvae in the lake.<ref>Dzyuba, E.V. (2006). Two coexisting species of Baikal golomyankas, Comephorus baicalensis and C. dybowski: seasonal dynamics of juveniles and their feeding. Hydrobiologia 568, Supplement 1: 111–114.</ref> Large shoals are not known for this species, although groups of up to about 20 individuals have been recorded near the lake bottom.<ref name=scfh/> Females are more common than males, which only make up about 32% of the population in the little Baikal oilfish and 17% in the big Baikal oilfish.<ref name=Fishwatching2016b/> The females do not lay eggs; rather, they are viviparous, giving birth to a swarm of 2000–3000 larvae.<ref name=bww/> Females containing developing embryos can be seen year-round,<ref name=Fishwatching2016b/> but there does appear to be a level of seasonality in the birth, with the largest number of larvae occurring from August to April (some differences in the peak timing between the two species).<ref name=Fishwatching2016a/> Most females die after giving birth.<ref name=irkutsk/> It has been claimed that their bellies burst open to release the young, killing the female in the process, but this is a myth.<ref name=scfh/> Golomyanka can reach an age of up to 6–8 years.<ref name=irkutsk/><ref name=Fishwatching2016b/>
They are sluggish fish,<ref>Jakubowski, Tugarina, and Żuwała (2003). Pectoral fin development in the Baikalian viviparous golomyankas (Comephoridae; Cottoidei), with a remark on eggs and embryos of Comephorus baicalensis (Pallas). J.Anat. 203(3): 317–322.</ref> and have relatively large mouths with several rows of somewhat brush-like teeth, allowing them to sift out fine organisms from the water.<ref name=Fishwatching2016b/> They primarily feed on the planktonic copepod ''Epischura baikalensis'', the amphipod crustacean ''Macrohectopus branickii'' and larvae of sculpins,<ref>Miyasaka, Dzyuba, Genkai-Kato and Wada (2006). Feeding ecology of two planktonic sculpins, Comephorus baicalensis and Comephorus dybowskii (Comephoridae), in Lake Baikal. Ichthyological Research 53(4): 419–422.</ref> including those of their own species.<ref name=1baikalKTB/>
==Relationship to humans== [[File:Ice-fishing on Baikal 5.jpg|thumb|A few golomyankas (for example, the pinkish fish on the upper-center part of the photo and another in the lower-left), as well as several whitefish, Baikal yellowfins and amphipods caught during icefishing using a net]]
Despite being numerous in the lake, golomyankas are difficult to catch in large quantities as they do not gather in large schools.<ref name=scfh/> Golomyankas are not harvested commercially, although their fats and oils were used in lamps and as traditional medicine by native Siberians when storms tossed the fish up on shore.<ref name=bww/> They are of no value as a food source for humans, dogs or cats, but are the primary food source for the Baikal seal, and also eaten by other fish in the lake.<ref name=scfh/><ref name=1baikalKTB/> They are so numerous and spawn so rapidly that they represent the largest concentration of fish biomass within the entire lake, and would seriously unbalance the ecosystem of Lake Baikal if not constantly preyed upon by predators.
==See also== * List of fish families
==References== {{Reflist|30em}} * [https://web.archive.org/web/20060622025817/http://www.baikal.ru/old.baikal.ru/baikal/faq/b3e.htm Lake Baikal FAQ] Irkutsk State University Lake Baikal FAQ, accessed May 5, 2006
{{commons category|Comephorus}}
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Category:Comephorus Category:Cottoidei Category:Scorpaeniformes genera Category:Viviparous fish Category:Taxa named by Bernard Germain de Lacépède Category:Endemic fauna of Russia Category:Fish of Lake Baikal