Reedfish

{{Short description|Species of fish}} {{Use dmy dates|date=June 2021}} {{Speciesbox | name = Reedfish | image = Akwa19 reedfish.jpg | image2 = Erpetoichthys calabaricus 01.jpg | status = NT | status_system = IUCN3.1 | status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Lalèyè, P. |author2=Moelants, T. |author3=Olaosebikan, B.D. |date=2020 |title=''Erpetoichthys calabaricus'' |volume=2020 |article-number=e.T182479A135026602 |doi=10.2305/IUCN.UK.2020-2.RLTS.T182479A135026602.en |access-date=19 November 2021}}</ref> | genus = Erpetoichthys | parent_authority = J. A. Smith, 1865 | species = calabaricus | authority = J. A. Smith, 1865 | range_map = Erpetoichthys calabaricus Map.jpg | synonyms = *''Calamoichthys calabaricus'' (Smith 1865) Smith 1866 *''Erpetoichthys robbianus'' Smith 1865 *''Polypterus erpetoideus'' Smith 1865 | synonyms_ref = <ref>{{cite web|last=Froese|first=R.|last2=Pauly|first2=D.|year=2017|title=Polypteridae |url=http://www.fishbase.se/Summary/FamilySummary.php?ID=31|website=FishBase|access-date=18 May 2017}}</ref><ref>{{cite web|title=Polypteridae|url=http://deeplyfish.com/wp-content/uploads/2017/05/Family-Polypteridae-PDF.pdf|website=Deeplyfish- fishes of the world|access-date=18 May 2017|archive-date=2 August 2017|archive-url=https://web.archive.org/web/20170802123230/http://deeplyfish.com/wp-content/uploads/2017/05/Family-Polypteridae-PDF.pdf}}</ref> }}

The '''reedfish''', '''ropefish''' (more commonly used in the United States), or '''snakefish''', '''''Erpetoichthys calabaricus''''', is a species of fish in the family Polypteridae alongside the bichirs. It is the only member of the genus '''''Erpetoichthys'''''. It is native to fresh and brackish waters in West and Central Africa. The reedfish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. It is threatened by habitat loss through palm oil plantations, other agriculture, deforestation, and urban development.<ref name="iucn status 19 November 2021" />

==Description== The largest confirmed reedfish museum specimen was {{cvt|37|cm}} long,<ref name=fishbase>{{FishBase|genus=Erpetoichthys|species=calabaricus|year=2014|month=March}}</ref><ref name=PFK>{{cite web| title=A breeding first: The Reedfish | url=https://www.practicalfishkeeping.co.uk/features/a-breeding-first-the-reedfish/ | publisher=Practical Fishkeeping | access-date=16 June 2022 }}</ref> and three studies where more than 2,000 wild reedfish were caught (using basket traps, meaning that only individuals longer than {{cvt|15-20|cm|disp=sqbr|0}} were retained) found none that exceeded {{cvt|41.4|cm}}.<ref>{{cite journal| last=King | first=R.P. | year=1996 | title=Length-weight relationships of Nigerian freshwater fishes | journal=The WorldFish Center | volume=19 | issue=3 | pages=49-52 }}</ref><ref>{{cite journal| last=Ekpe | first=A.I. | last2=Asikpo | first2=E.-I. M. | year=2019 | title=Sex ratio, size structure and condition index in the rope fish, Erpetoichthys calabaricus (Polypteridae) from a Niger Delta flood plain, Nigeria | journal=International Journal of Fisheries and Aquatic Studies | volume=7 | issue=1 | pages=205-209 }}</ref><ref name=Amiekan2020>{{cite journal| last=Amiekan | first=N.A. | last2=Udo | first2=M.T. | last3=Brownson | first3=I.I. | last4=Obot | first4=O.I. | last5=Ekpo | first5=I.E. | year=2020 | title=Population dynamics of Calabar snakefish (= reed fish), Erpetoichthys calabaricus. (Teleostei: Polypteridae) (Smith, 1866) at Ibikpe Creek in Uruan, Nigeria | journal=Journal of Wetlands and Waste Management | volume=4 | issue=1 | pages=66-77 }}</ref> Although sometimes claimed to reach up to {{cvt|90|cm|ft|0}} long,<ref>{{cite web| title=Erpetoichthys calabaricus | url=https://www.seriouslyfish.com/species/erpetoichthys-calabaricus/ | publisher=SeriouslyFish | access-date=16 June 2022 }}</ref><ref name=TFH>{{cite web| title=Understanding the Reedfish | url=https://www.tfhmagazine.com/articles/freshwater/understanding-the-reedfish | publisher=TFH Magazine | access-date=16 June 2022 }}</ref> this is incorrect.<ref name=Moritz2019>{{cite journal| last=Moritz | first=T. | last2=Britz | first2=R. | year=2019 | title=Revision of the extant Polypteridae (Actinopterygii: Cladistia) | journal=Ichthyological Exploration of Freshwaters | doi=10.23788/IEF-1094 }}</ref> The sexes are very similar in both median and maximum length, but females average heavier than males of a similar length, and they can be reliably separated by the shape of their anal fin.<ref name=Moritz2019/><ref name=Asuquo2019>{{cite journal| last=Asuquo | first=I.E. | last2=Essien-Ibok | first2=M.A. | year=2019 | title=Sexual Dimorphism in Erpetoicthys calabaricus from a Mangrove Creek, Nigeria | journal=Asian Journal of Fisheries and Aquatic Research | volume=2 | issue=3 | pages=1-9 }}</ref> Reedfish are dark above and on the sides, with lighter orangish or yellowish underparts.<ref name=Moritz2019/> Males are generally more olive-green in colour, whereas females generally are more yellowish-brown.<ref name=Asuquo2019/> Larvae have conspicuous external gills, making them resemble salamander larvae.<ref name=fishbase/>

Body elongation in fishes, such as eels, usually happens through the addition of caudal (tail) vertebrae, but in bichirs it has happened through the addition of precaudal vertebrae. Reedfish have evolved a more snakelike body by having twice as many precaudal vertebrae as the members of its sister genus ''Polypterus'', despite having the same number of tail vertebrae.<ref>[https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.21491 Effects of Precaudal Elongation on Visceral Topography in a Basal Clade of Ray-Finned Fishes]</ref> Unlike ''Polypterus'', ''Erpetoichthys'' lack pelvic fins and the subopercle,<ref>Claeson K.M., Bemis W.E., Hagadorn J.W. New interpretations of the skull of a primitive bony fish Erpetoichthys calabaricus (Actinopterygii: Cladistia) Journal of Morphology, 268 (2007), pp. 1021-1039 [https://doi.org/10.1002/jmor.10567 DOI]</ref> and the long dorsal fin, which consists of a series of well-separated "spines", are each supported by a single fin ray rather than multiple rays as in ''Polypterus''.<ref>Otero O., Likius A., Vignaud P., Brunet M. A new polypterid fish: Polypterus faraou sp. nov. (Cladistia, Polypteriformes) from the late Miocene, Toros-Menalla, Chad Zoological Journal of the Linnean Society, 146 (2006), pp. 227-237 [https://doi.org/10.1111/j.1096-3642.2006.00201.x DOI]</ref> The reedfish possesses a pair of lungs, enabling it to breathe atmospheric air. This allows the species to survive in water with low dissolved oxygen content and to survive for an intermediate amount of time out of water.<ref name=fishbase/>

The genus name derives from the Greek words ''erpeton'' (creeping thing) and ''ichthys'' (fish).<ref>{{cite book|first1=L.|last1=Fishelson|title=Zoology|year=1984|publisher=Hakibutz Hameuchad Publishing House|location=Israel|volume=2|page=126}}</ref>

==Distribution and habitat== The reedfish inhabits slow-moving or standing, fresh or brackish, relatively warm tropical water, and usually in places with reeds or other dense plant growth. It occurs in Benin, Cameroon and Nigeria, spanning the area from the Ouémé River to the Sanaga River.<ref name="iucn status 19 November 2021"/><ref name=Moritz2019/> There are old records from the Chiloango River in DR Congo and Cabinda in Angola, but these are unconfirmed and questionable.<ref name="iucn status 19 November 2021"/><ref name=Moritz2019/>

==Ecology== The reedfish is nocturnal, and feeds on annelid worms, small crustaceans (such as shrimp), insects (both adults and their larvae), snails and small fish.<ref name=fishbase/><ref name=TFH/><ref>{{cite web | last=Milner | first=J. | date=4 October 2021 | title=Rope Fish Profile: Care, Tanking and Feeding | url=https://theaquarium.club/rope-fish/ | publisher=The Aquarium Club | access-date=16 June 2022 }}</ref> When moving through water slowly, it tends to use its pectoral fins, and when moving quickly changes to an eel-like form of swimming (making more use of full-body movements and the caudal fin). Unlike their sister genus ''Polypterus'', which does not leave water voluntarily,<ref>{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0944200616300265 | doi=10.1016/j.zool.2016.05.001 | pmid=27267147 | bibcode=2016Zool..119..447S | title=Locomotor flexibility of ''Polypterus senegalus'' across various aquatic and terrestrial substrates | last1=Standen | first1=Emily M. | last2=Du | first2=Trina Y. | last3=Laroche | first3=Philippe | last4=Larsson | first4=Hans C. E. | journal=Zoology | date=2016 | volume=119 | issue=5 | pages=447–454 | url-access=subscription }}</ref> reedfish are known to explore land both in the wild and in captivity if given the opportunity, slithering along like a snake and also taking food items on land.<ref name=locomotor>{{cite journal|title=Locomotor behavior across an environmental transition in the ropefish, ''Erpetoichthys calabaricus''|journal=Journal of Experimental Biology|date=15 February 2011|issn=0022-0949|pmid=21270300|pages=530–537|volume=214|issue=4|doi=10.1242/jeb.047902|first1=Cinnamon M.|last1=Pace|first2=Alice C.|last2=Gibb|doi-access=free}}</ref> Prey captured on land is brought back to the water.<ref>{{cite journal | doi=10.1002/ece3.2694 | title=Terrestrial capture of prey by the reedfish, a model species for stem tetrapods | date=2017 | last1=Van Wassenbergh | first1=Sam | last2=Bonte | first2=Christoffel | last3=Michel | first3=Krijn B. | journal=Ecology and Evolution | volume=7 | issue=11 | pages=3856–3860 | pmid=28616182 | pmc=5468123 | bibcode=2017EcoEv...7.3856V }}</ref>

Females repeatedly deposit small batches of eggs between the anal fins of the male, where they are fertilized. The male reedfish then scatters the eggs among aquatic vegetation, where they stick to plants and substrate. Larvae hatch rapidly (after 70 hours) but remain attached to vegetation; they become independent and start to feed after ~22 days, when the egg's yolk sac has been consumed.<ref name=fishbase/> [[File:Erpetoichthys calabaricus.jpg|thumb|A yellowish-green ropefish amongst grey ''Polypterus senegalus'']]

==Relation to humans== In coastal central Africa, the species is threatened by habitat loss driven by the development of oil palm plantations. Populations in western Africa are impacted by degradation and loss of habitat from wetland drainage for agricultural and urban developments. The reedfish is currently classified as Near Threatened by the IUCN.<ref name="iucn status 19 November 2021" /> It is regarded as a good food fish and commonly caught in the local subsistence fishery. It is also regularly caught for the international aquarium fish trade. Overall, catch levels do not appear to represent a major threat to the species at present, but do need monitoring.<ref name=Amiekan2020/>

===In the aquarium=== Reedfish are sometimes displayed in aquaria. All aquarium fish are wild-caught; they have not yet been successfully bred in captivity. Spawning and hatching in captivity has been observed, but no hatchlings have been reported to survive to adulthood.<ref name=PFK/><ref>{{Cite web | url=https://www.fishkeeper.co.uk/databank/reed-fish-rope-fish | title=Reed Fish - Maidenhead Aquatics}}</ref>

They are inquisitive, peaceful, and have some "personality". Although nocturnal, reedfish will sometimes come out during the day. Since they have a peaceful nature, other fish may "bully" a reedfish, despite its large size, especially in competition for food or space.<ref name=aqua-fish>[https://en.aqua-fish.net/fish/ropefish A profile of Ropefish] Retrieved 2 August 2017.</ref> Some reedfish also have an inclination to stay close to the water surface, where they will be safe from other fish and will even allow most of their bodies to leave the water at times.{{citation needed|date=April 2017}}

They can be difficult to keep; they will jump and enter pumps to escape tanks and frequently die as a result, and they can be sensitive to pH swings and nitrogen chemistry.<ref>{{cite journal|url=http://www.tfhmagazine.com/details/articles/understanding-the-reedfish.htm|title=Understanding the Reedfish|author=Phil Purser|journal=Tropical Fish Magazine|date=August 2007}}</ref><ref>{{cite web|url=http://www.aquahobby.com/gallery/e_reed.php|title=Erpetoichthys calabaricus|publisher=The Age of Aquariums|access-date=2 August 2017}}</ref><ref name=aqua-fish/> They will often consume other smaller fish when given the opportunity.<ref name=aqua-fish/> Often small feeder goldfish and minnows are eaten in place of bloodworms or nightcrawlers, and other commercially available live fish food.{{citation needed|date=February 2016}}

==References== {{Reflist}}

Category:Polypteridae Category:Taxa named by John Alexander Smith (zoologist) Category:Freshwater fish of Africa  Category:Fish described in 1865