| Reedfish | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Polypteriformes |
| Family: | Polypteridae |
| Genus: | Erpetoichthys J. A. Smith, 1865 |
| Species: | E. calabaricus |
| Binomial name | |
| Erpetoichthys calabaricus J. A. Smith, 1865 | |
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| Synonyms[2][3] | |
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Thereedfish,ropefish (more commonly used in the United States), orsnakefish,Erpetoichthys calabaricus, is aspecies of fish in thefamilyPolypteridae alongside the bichirs. It is theonly member of thegenusErpetoichthys. It is native to fresh andbrackish waters inWest andCentral Africa. The reedfish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. It is threatened byhabitat loss throughpalm oil plantations, other agriculture, deforestation, and urban development.[1]
The largest confirmed reedfishmuseum specimen was 37 cm (15 in) long,[4][5] and three studies where more than 2,000 wild reedfish were caught (usingbasket traps, meaning that only individuals longer than 15–20 cm [6–8 in] were retained) found none that exceeded 41.4 cm (16.3 in).[6][7][8] Although sometimes claimed to reach up to 90 cm (3 ft) long,[9][10] this is incorrect.[11]
Body elongation in fishes, such as eels, usually happens through the addition of caudal (tail) vertebrae, but inbichirs 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 genusPolypterus, despite having the same number of tail vertebrae.[12]Pelvic fins are absent, and the longdorsal fin consist of a series of well-separated spines, each supporting one or several articulated rays and a membrane. The reedfish possesses a pair oflungs, enabling it to breathe atmospheric air. This allows the species to survive in water with lowdissolved oxygen content and to survive for an intermediate amount of time out of water.[4] 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 theiranal fin.[11][13] Reedfish are dark above and on the sides, with lighter orangish or yellowish underparts.[11] Males are generally moreolive-green in colour, whereas females generally are more yellowish-brown.[13]Larvae have conspicuous external gills, making them resemblesalamander larvae.[4]
Thegenus name derives from theGreek wordserpeton (creeping thing) andichthys (fish).[14]
The reedfish inhabits slow-moving or standing, fresh orbrackish, relatively warm tropical water, and usually in places withreeds or other dense plant growth. It occurs inBenin,Cameroon andNigeria, spanning the area from theOuémé River to theSanaga River.[1][11] There are old records from theChiloango River inDR Congo andCabinda inAngola, but these are unconfirmed and questionable.[1][11]
The reedfish isnocturnal, and feeds onannelid worms, smallcrustaceans (such asshrimp),insects (both adults and their larvae),snails and small fish.[4][10][15] 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 genusPolypterus, which does not leave water voluntarily,[16] 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.[17] Prey captured on land is brought back to the water.[18]
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'syolk sac has been consumed.[4]
In coastal central Africa, the species is threatened byhabitat loss driven by the development ofoil 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 asNear Threatened by theIUCN.[1] It is regarded as a good food fish and commonly caught in the localsubsistence 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.[8]
Reedfish are sometimes displayed inaquaria. 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.[5][19]
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.[20] 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]
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.[21][22][20] They will often consume other smaller fish when given the opportunity.[20] Often small feedergoldfish andminnows are eaten in place ofbloodworms ornightcrawlers, and other commercially available live fish food.[citation needed]
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