# Cavefish

Cavefish or cave fish is a generic term for fresh and brackish water fish adapted to life in caves and other underground habitats. Related terms are subterranean fish, troglomorphic fish, troglobitic fish, stygobitic fish, phreatic fish, and hypogean fish.
There are more than 200 scientifically described species of obligate cavefish found on all continents, except Antarctica. Although widespread as a group, many species have very small ranges and are threatened.
Cavefish are members of a wide range of families and do not form a monophyletic group. Typical adaptations include reduced eyes and depigmentation.

## Adaptations

Many aboveground fish may enter caves on occasion, but obligate cavefish (fish that require underground habitats) are extremophiles with a number of unusual adaptations known as troglomorphism. In some species, notably the Mexican tetra, shortfin molly, Oman garra, Indoreonectes evezardi, and a few catfish, both "normal" aboveground and cavefish forms exist.
Many adaptions seen in cavefish are aimed at surviving in a habitat with little food. Living in darkness, pigmentation and eyes are useless, or an actual disadvantage because of their energy requirements, and therefore typically reduced in cavefish. Other examples of adaptations are larger fins for more energy-efficient swimming, and a loss of scales and swim bladder. The loss can be complete or only partial, for example resulting in small or incomplete (but still existing) eyes, and eyes can be present in the earliest life stages but degenerated by the adult stage. In some cases, "blind" cavefish may still be able to see: Juvenile Mexican tetras of the cave form are able to sense light via certain cells in the pineal gland (pineal eye), and Congo blind barbs are photophobic, despite only having retinas and optical nerves that are rudimentary and located deep inside the head, and completely lacking a lens. In the most extreme cases, the lack of light has changed the circadian rhythm (24-hour internal body clock) of the cavefish. In the Mexican tetra of the cave form and in Garra andruzzii the circadian rhythm lasts 30 hours and 47 hours, respectively. This may help them to save energy. Without sight, other senses are used and these may be enhanced. Examples include the lateral line for sensing vibrations, mouth suction to sense nearby obstacles (comparable to echolocation), and chemoreception (via smell and taste buds). Although there are cavefish in groups known to have electroreception (catfish and South American knifefish), there is no published evidence that this is enhanced in the cave-dwellers. The level of specialized adaptations in a cavefish is generally considered to be directly correlated to the amount of time it has been restricted to the underground habitat: Species that recently arrived show few adaptations and species with the largest number of adaptations are likely the ones that have been restricted to the habitat for the longest time.
Some fish species that live buried in the bottom of aboveground waters, live deep in the sea or live in deep rivers have adaptations similar to cavefish, including reduced eyes and pigmentation.
Cavefish are quite small with most species being between 2 and 13 cm (0.8–5.1 in) in standard length and about a dozen species reaching 20–23 cm (8–9 in). Only three species grow larger; two slender Ophisternon swamp eels at up to 32–36 cm (13–14 in) in standard length and a much more robust undescribed species of mahseer at 43 cm (17 in). The very limited food resources in the habitat likely prevents larger cavefish species from existing and also means that cavefish in general are opportunistic feeders, taking whatever is available. In their habitat, cavefish are often the top predators, feeding on smaller cave-living invertebrates, or are detritivores without enemies. Cavefish typically have low metabolic rates and may be able to survive long periods of starvation. A captive Phreatobius cisternarum did not feed for a year, but remained in good condition. The cave form of the Mexican tetra can build up unusually large fat reserves by "binge eating" in periods where food is available, which then (together with its low metabolic rate) allows it to survive without food for months, much longer than the aboveground form of the species.
In the dark habitat, certain types of displays are reduced in cavefish, but in other cases they have become stronger, shifting from displays that are aimed at being seen to displays aimed at being felt via water movement. For example, during the courtship of the cave form of the Mexican tetra the pair produce turbulence through exaggerated gill and mouth movements, allowing them to detect each other. In general, cavefish are slow growers and slow breeders. Breeding behaviors among cavefish vary extensively, and there are both species that are egg-layers and ovoviviparous species that give birth to live young. Uniquely among fish, the genus Amblyopsis brood their eggs in the gill chambers (somewhat like mouthbrooders).

## Habitat

Although many cavefish species are restricted to underground lakes, pools or rivers in actual caves, some are found in aquifers and may only be detected by humans when artificial wells are dug into this layer. Most live in areas with low (essentially static) or moderate water current, but there are also species in places with very strong current, such as the waterfall climbing cavefish. Underground waters are often very stable environments with limited variations in temperature (typically near the annual average of the surrounding region), nutrient levels and other factors. Organic compounds generally only occur in low levels and rely on outside sources, such as contained in water that enters the underground habitat from outside, aboveground animals that find their way into caves (deliberately or by mistake) and guano from bats that roost in caves. Cavefish are primarily restricted to freshwater. A few species, notably the cave-dwelling viviparous brotulas, Luciogobius gobies, Milyeringa sleeper gobies and the blind cave eel, live in anchialine caves and several of these tolerate various salinities.

## Range and diversity

The more than 200 scientifically described obligate cavefish species are found in most continents, but there are strong geographic patterns and the species richness varies. The vast majority of species are found in the tropics or subtropics. Cavefish are strongly linked to regions with karst, which commonly result in underground sinkholes and subterranean rivers.
With more than 120 described species, by far the greatest diversity is in Asia, followed by more than 30 species in South America and about 30 species in North America. In contrast, only 9 species are known from Africa, 5 from Oceania, and 1 from Europe. On a country level, China has the greatest diversity with more than 80 species, followed by Brazil with more than 20 species. India, Mexico, Thailand and the United States of America each have 9–14 species. No other country has more than 5 cavefish species.
Being underground, many places where cavefish may live have not been thoroughly surveyed. New cavefish species are described with some regularity and undescribed species are known. As a consequence, the number of known cavefish species has risen rapidly in recent decades. In the early 1990s only about 50 species were known, in 2010 about 170 species were known, and by 2015 this had surpassed 200 species. It has been estimated that the final number might be around 250 obligate cavefish species. For example, the first cavefish in Europe, a Barbatula stone loach, was only discovered in 2015 in Southern Germany, and the largest known cavefish, Neolissochilus pnar (originally thought to be a form of the golden mahseer), was only definitely confirmed in 2019, despite being quite numerous in the cave where it occurs in Meghalaya, India. Conversely, their unusual appearance means that some cavefish already attracted attention in ancient times. The oldest known description of an obligate cavefish, involving Sinocyclocheilus hyalinus, is almost 500 years old.
Obligate cavefish are known from a wide range of families: Characidae (characids), Balitoridae (hillstream loaches), Cobitidae (true loaches), Cyprinidae (carps and allies), Nemacheilidae (stone loaches), Amblycipitidae (torrent catfishes), Astroblepidae (naked sucker-mouth catfishes), Callichthyidae (armored catfishes), Clariidae (airbreathing catfishes), Heptapteridae (heptapterid catfishes), Ictaluridae (ictalurid catfishes), Kryptoglanidae (kryptoglanid catfish), Loricariidae (loricariid catfishes), Phreatobiidae (phreatobiid catfishes), Trichomycteridae (pencil catfishes), Sternopygidae (glass knifefishes), Amblyopsidae (U.S. cavefishes), Bythitidae (brotulas), Poeciliidae (live-bearers), Synbranchidae (swamp eels), Cottidae (true sculpins), Butidae (butid gobies), Eleotridae (sleeper gobies), Milyeringidae (blind cave gobies), Gobiidae (gobies) and Channidae (snakeheads). Many of these families are only very distantly related and do not form a monophyletic group, showing that adaptations to a life in caves has happened numerous times among fish. As such, their similar adaptions are examples of convergent evolution and the descriptive term "cavefish" is an example of folk taxonomy rather than scientific taxonomy. Strictly speaking some Cyprinodontidae (pupfish) are also known from sinkhole caves, famously including the Devils Hole pupfish, but these lack the adaptations (e.g., reduced eyes and pigmentation) typically associated with cavefish. Additionally, species from a few families such as Chaudhuriidae (earthworm eels), Glanapteryginae and Sarcoglanidinae live buried in the bottom of aboveground waters, and can show adaptions similar to traditional underground-living (troglobitic) fish. It has been argued that such species should be recognized as a part of the group of troglobitic fish.

### Species

As of 2019, the following underground-living fish species with various levels of troglomorphism (ranging from complete loss of eyes and pigment, to only a partial reduction of one of these) are known. Phreatobius sanguijuela and Prietella phreatophila, the only species with underground populations in more than one country, are listed twice. Excluded from the table are species that live buried in the bottom of aboveground waters (even if they have troglomorphic-like features) and undescribed species.
| Family | Species | Country | Year of description | Notes |
| Characidae | Astyanax aeneus | Mexico | 1860 | Species includes both aboveground and belowground forms (aboveground also in Central America). Sometimes considered a part of Astyanax mexicanus |
| Characidae | Astyanax mexicanus (blind cave tetra) | Mexico | 1853 | Species includes both aboveground and belowground forms (aboveground also in United States). Cave form sometimes considered a separate species, A. jordani |
| Characidae | Stygichthys typhlops (Brazilian blind characid) | Brazil | 1965 | |
| Cyprinidae | Anchicyclocheilus halfibindus | China | 1992 | Sometimes considered a species in the genus Sinocyclocheilus, or a synonym of Sinocyclocheilus microphthalmus |
| Cyprinidae | Barbodes microps | Indonesia | 1868 | Formerly placed in Barbus or Puntius instead. Aboveground populations have also been assigned to this species, but its taxonomy is unresolved and a review has suggested that at least some of the underground populations might belong to Puntius binotatus or an undescribed species instead. |
| Cyprinidae | Barbopsis devecchi (Somalian blind barb) | Somalia | 1926 | |
| Cyprinidae | Caecobarbus geertsii (Congo blind barb) | DR Congo | 1921 | |
| Cyprinidae | Caecocypris basimi (Haditha cavefish) | Iraq | 1980 | |
| Cyprinidae | Garra barreimiae (Omani blind cavefish) | Oman | 1956 | Species includes both aboveground and belowground forms (aboveground also in the United Arab Emirates). A population in the United Arab Emirates has been reported to be underground, but this is incorrect |
| Cyprinidae | Garra dunsirei (Tawi Atair garra) | Oman | 1987 | |
| Cyprinidae | Garra lorestanensis | Iran | 2016 | |
| Cyprinidae | Garra tashanensis | Iran | 2016 | |
| Cyprinidae | Garra typhlops (Iran cave barb) | Iran | 1944 | Formerly in its own genus Iranocypris |
| Cyprinidae | Garra widdowsoni (Iraq blind barb) | Iraq | 1955 | Formerly in its own genus Typhlogarra, but genetics show that it belongs in Garra |
| Cyprinidae | Longanalus macrochirous | China | 2006 | |
| Cyprinidae | Neolissochilus pnar | India | 2023 | Originally tentatively identified as a troglobitic form of the golden mahseer. |
| Cyprinidae | Neolissochilus subterraneus | Thailand | 2003 | |
| Cyprinidae | Garra andruzzii | Somalia | 1924 | Originally described in the monotypic genus Phreatichthys |
| Cyprinidae | Poropuntius speleops | Thailand | 1991 | |
| Cyprinidae | Sinocyclocheilus albeoguttatus | China | 1998 | |
| Cyprinidae | Sinocyclocheilus altishoulderus | China | 1992 | |
| Cyprinidae | Sinocyclocheilus aluensis | China | 2005 | |
| Cyprinidae | Sinocyclocheilus anatirostris (duck-billed golden-line fish) | China | 1986 | |
| Cyprinidae | Sinocyclocheilus angularis (gold-colored angle fish) | China | 1990 | |
| Cyprinidae | Sinocyclocheilus anophthalmus (eyeless golden-line fish) | China | 1988 | |
| Cyprinidae | Sinocyclocheilus anshuiensis | China | 2013 | |
| Cyprinidae | Sinocyclocheilus aquihornes | China | 2007 | |
| Cyprinidae | Sinocyclocheilus biangularis | China | 1996 | |
| Cyprinidae | Sinocyclocheilus bicornutus | China | 1997 | |
| Cyprinidae | Sinocyclocheilus brevibarbatus | China | 2009 | |
| Cyprinidae | Sinocyclocheilus broadihornes | China | 2007 | |
| Cyprinidae | Sinocyclocheilus cyphotergous | China | 1988 | |
| Cyprinidae | Sinocyclocheilus flexuosdorsalis | China | 2012 | |
| Cyprinidae | Sinocyclocheilus furcodorsalis (crossed-fork back golden-line fish) | China | 1997 | |
| Cyprinidae | Sinocyclocheilus guanyangensis | China | 2016 | |
| Cyprinidae | Sinocyclocheilus huanjiangensis | China | 2010 | |
| Cyprinidae | Sinocyclocheilus hugeibarbus | China | 2003 | |
| Cyprinidae | Sinocyclocheilus hyalinus (hyaline fish) | China | 1993 | |
| Cyprinidae | Sinocyclocheilus jinxiensis | China | 2012 | Proposed moved to monotypic genus Pseudosinocyclocheilus in 2016 |
| Cyprinidae | Sinocyclocheilus jiuxuensis | China | 2003 | |
| Cyprinidae | Sinocyclocheilus lingyunensis | China | 2000 | |
| Cyprinidae | Sinocyclocheilus longibarbatus | China | 1989 | |
| Cyprinidae | Sinocyclocheilus longifinus | China | 1996 | |
| Cyprinidae | Sinocyclocheilus luolouensis | China | 2013 | |
| Cyprinidae | Sinocyclocheilus luopingensis | China | 2002 | |
| Cyprinidae | Sinocyclocheilus macrophthalmus | China | 2001 | |
| Cyprinidae | Sinocyclocheilus macroscalus | China | 2000 | |
| Cyprinidae | Sinocyclocheilus maculatus | China | 2000 | |
| Cyprinidae | Sinocyclocheilus maitianheensis | China | 1992 | |
| Cyprinidae | Sinocyclocheilus malacopterus | China | 1985 | |
| Cyprinidae | Sinocyclocheilus mashanensis | China | 2010 | |
| Cyprinidae | Sinocyclocheilus microphthalmus (small eye golden-line fish) | China | 1989 | |
| Cyprinidae | Sinocyclocheilus multipunctatus | China | 1931 | |
| Cyprinidae | Sinocyclocheilus oxycephalus | China | 1985 | |
| Cyprinidae | Sinocyclocheilus purpureus | China | 1985 | |
| Cyprinidae | Sinocyclocheilus qiubeiensis | China | 2002 | |
| Cyprinidae | Sinocyclocheilus rhinocerous | China | 1994 | |
| Cyprinidae | Sinocyclocheilus robustus | China | 1988 | |
| Cyprinidae | Sinocyclocheilus tianeensis | China | 2003 | |
| Cyprinidae | Sinocyclocheilus tianlinensis | China | 2004 | |
| Cyprinidae | Sinocyclocheilus tileihornes | China | 2003 | |
| Cyprinidae | Sinocyclocheilus xunlensis | China | 2004 | |
| Cyprinidae | Sinocyclocheilus yishanensis | China | 1992 | |
| Cyprinidae | Speolabeo hokhanhi | Vietnam | 2018 | |
| Cyprinidae | Speolabeo musaei | Laos | 2011 | Formerly in genus Bangana |
| Cyprinidae | Troglocyclocheilus khammouanensis | Laos | 1999 | |
| Cyprinidae | Typhlobarbus nudiventris | China | 1982 | |
| Balitoridae | Cryptotora thamicola (waterfall climbing cavefish) | Thailand | 1988 | |
| Cobitidae | Bibarba parvoculus | China | 2015 | |
| Cobitidae | Cobitis damlae | Turkey | 2014 | First described as a species of cavefish based on a single specimen, but a later review suggested that it was found in an area without underground waters and only is an albinistic individual of the aboveground Cobitis fahireae |
| Cobitidae | Pangio bhujia | India | 2019 | |
| Cobitidae | Protocobitis anteroventris | China | 2013 | |
| Cobitidae | Protocobitis polylepis | China | 2008 | |
| Cobitidae | Protocobitis typhlops | China | 1993 | |
| Nemacheilidae | Barbatula barbatula (stone loach) | Germany | 1758 | Aboveground populations widespread in Europe. Belowground population only discovered in 2015 and tentatively included in this species based on genetic evidence. Only known cavefish in Europe |
| Nemacheilidae | Claea dabryi | China | 1874 | Traditionally in genus Schistura or Triplophysa. Species includes both aboveground and belowground populations; the latter sometimes recognized as a separate subspecies microphthalmus. |
| Nemacheilidae | Draconectes narinosus | Vietnam | 2012 | |
| Nemacheilidae | Eidinemacheilus proudlovei | Iraq | 2016 | |
| Nemacheilidae | Eidinemacheilus smithi (Zagroz blind loach) | Iran | 1976 | Formerly in genus Noemacheilus or Paracobitis |
| Nemacheilidae | Heminoemacheilus hyalinus | China | 1996 | |
| Nemacheilidae | Indoreonectes evezardi | India | 1872 | Species includes both aboveground and belowground forms |
| Nemacheilidae | Nemacheilus troglocataractus (blind cave loach) | Thailand | 1989 | |
| Nemacheilidae | Oreonectes acridorsalis | China | 2013 | |
| Nemacheilidae | Oreonectes anophthalmus | China | 1981 | |
| Nemacheilidae | Oreonectes barbatus | China | 2013 | |
| Nemacheilidae | Oreonectes daqikongensis | China | 2016 | |
| Nemacheilidae | Oreonectes donglanensis | China | 2013 | |
| Nemacheilidae | Oreonectes duanensis | China | 2013 | |
| Nemacheilidae | Oreonectes elongatus | China | 2012 | |
| Nemacheilidae | Oreonectes furcocaudalis | China | 1987 | |
| Nemacheilidae | Oreonectes guananensis | China | 2011 | |
| Nemacheilidae | Oreonectes luochengensis | China | 2011 | |
| Nemacheilidae | Oreonectes macrolepis | China | 2009 | |
| Nemacheilidae | Oreonectes microphthalmus | China | 2008 | |
| Nemacheilidae | Oreonectes shuilongensis | China | 2016 | |
| Nemacheilidae | Oreonectes translucens | China | 2006 | |
| Nemacheilidae | Schistura deansmarti | Thailand | 2003 | |
| Nemacheilidae | Schistura jarutanini | Thailand | 1990 | |
| Nemacheilidae | Schistura kaysonei | Laos | 2002 | |
| Nemacheilidae | Schistura larketensis | India | 2017 | |
| Nemacheilidae | Schistura lingyunensis | China | 1997 | Sometimes in genus Triplophysa |
| Nemacheilidae | Schistura mobbsi | Vietnam | 2012 | |
| Nemacheilidae | Schistura oedipus | Thailand | 1988 | |
| Nemacheilidae | Schistura papulifera | India | 2007 | |
| Nemacheilidae | Schistura sijuensis | India | 1987 | |
| Nemacheilidae | Schistura spekuli | Vietnam | 2004 | |
| Nemacheilidae | Schistura spiesi | Thailand | 2003 | |
| Nemacheilidae | Speonectes tiomanensis | Malaysia | 1990 | Formerly in genus Sundoreonectes |
| Nemacheilidae | Triplophysa aluensis | China | 2000 | |
| Nemacheilidae | Triplophysa dongganensis | China | 2013 | |
| Nemacheilidae | Triplophysa fengshanensis | China | 2013 | |
| Nemacheilidae | Triplophysa gejiuensis | China | 1979 | |
| Nemacheilidae | Triplophysa huanjiangensis | China | 2011 | |
| Nemacheilidae | Triplophysa jiarongensis | China | 2012 | |
| Nemacheilidae | Triplophysa langpingensis | China | 2013 | |
| Nemacheilidae | Triplophysa lihuensis | China | 2012 | |
| Nemacheilidae | Triplophysa longibarbata | China | 1998 | Includes Paracobitis maolanensis and P. posterodorsalus as synonyms, which may be valid species |
| Nemacheilidae | Triplophysa luochengensis | China | 2017 | |
| Nemacheilidae | Triplophysa macrocephala | China | 2011 | |
| Nemacheilidae | Triplophysa qiubeiensis | China | 2008 | |
| Nemacheilidae | Triplophysa rosa | China | 2005 | |
| Nemacheilidae | Triplophysa shilinensis | China | 1992 | |
| Nemacheilidae | Triplophysa tianeensis | China | 2004 | |
| Nemacheilidae | Triplophysa xiangshuingensis | China | 2004 | |
| Nemacheilidae | Triplophysa xiangxiensis | China | 1986 | |
| Nemacheilidae | Triplophysa yunnanensis | China | 1990 | |
| Nemacheilidae | Troglocobitis starostini (Starostin's loach) | Turkmenistan | 1983 | |
| Amblycipitidae | Xiurenbagrus dorsalis | China | 2014 | |
| Astroblepidae | Astroblepus pholeter | Ecuador | 1962 | |
| Astroblepidae | Astroblepus riberae | Peru | 1994 | |
| Callichthyidae | Aspidoras mephisto | Brazil | 2017 | Formerly included in aboveground species A. albater |
| Clariidae | Clarias cavernicola (golden cave catfish) | Angola | 1936 | |
| Clariidae | Horaglanis abdulkalami | India | 2012 | |
| Clariidae | Horaglanis alikunhii | India | 2004 | |
| Clariidae | Horaglanis krishnai (Indian blind catfish) | India | 1950 | |
| Clariidae | Uegitglanis zammaranoi | Somalia | 1923 | |
| Heptapteridae | Pimelodella kronei | Brazil | 1907 | |
| Heptapteridae | Pimelodella spelaea | Brazil | 2004 | |
| Heptapteridae | Rhamdia enfurnada | Brazil | 2005 | |
| Heptapteridae | Rhamdia guasarensis | Venezuela | 2004 | |
| Heptapteridae | Rhamdia laluchensis (La Lucha blind catfish) | Mexico | 2003 | |
| Heptapteridae | Rhamdia laticauda typhla | Belize | 1982 | Other subspecies found in aboveground habitats in Mexico and Central America |
| Heptapteridae | Rhamdia macuspanensis (Olmec blind catfish) | Mexico | 1998 | |
| Heptapteridae | Rhamdia quelen urichi | Trinidad | 1926 | Other subspecies found widely in aboveground habitats in South and Central America |
| Heptapteridae | Rhamdia reddelli (blind whiskered catfish) | Mexico | 1984 | |
| Heptapteridae | Rhamdia zongolicensis (Zongolica catfish) | Mexico | 1993 | |
| Heptapteridae | Rhamdiopsis krugi | Brazil | 2010 | |
| Ictaluridae | Prietella lundbergi (phantom blindcat) | Mexico | 1995 | |
| Ictaluridae | Prietella phreatophila (Mexican blindcat) | Mexico | 1954 | Listed twice (once for each country) |
| Ictaluridae | Prietella phreatophila (Mexican blindcat) | United States | 1954 | Listed twice (once for each country) |
| Ictaluridae | Satan eurystomus (widemouth blindcat) | United States | 1947 | |
| Ictaluridae | Trogloglanis pattersoni (toothless blindcat) | United States | 1919 | |
| Kryptoglanidae | Kryptoglanis shajii | India | 2011 | Found both underground and aboveground (not known to differ in appearance) |
| Loricariidae | Ancistrus cryptophthalmus | Brazil | 1987 | |
| Loricariidae | Ancistrus formoso | Brazil | 1997 | |
| Loricariidae | Ancistrus galani | Venezuela | 1994 | |
| Phreatobiidae | Phreatobius cisternarum | Brazil | 1905 | |
| Phreatobiidae | Phreatobius dracunculus | Brazil | 2007 | |
| Phreatobiidae | Phreatobius sanguijuela | Bolivia | 2007 | Listed twice (once for each country) |
| Phreatobiidae | Phreatobius sanguijuela | Brazil | 2007 | Listed twice (once for each country) |
| Siluridae | Pterocryptis buccata (cave sheatfish) | Thailand | 1998 | Species includes both aboveground and belowground forms |
| Siluridae | Pterocryptis cucphuongensis | Vietnam | 1978 | |
| Trichomycteridae | Glaphyropoma spinosum | Brazil | 2008 | |
| Trichomycteridae | Ituglanis bambui | Brazil | 2004 | |
| Trichomycteridae | Ituglanis boticario | Brazil | 2015 | |
| Trichomycteridae | Ituglanis epikarsticus | Brazil | 2004 | |
| Trichomycteridae | Ituglanis mambai | Brazil | 2008 | |
| Trichomycteridae | Ituglanis passensis | Brazil | 2002 | |
| Trichomycteridae | Ituglanis ramiroi | Brazil | 2004 | |
| Trichomycteridae | Silvinichthys bortayro | Argentina | 2005 | |
| Trichomycteridae | Trichomycterus dali | Brazil | 2011 | |
| Trichomycteridae | Trichomycterus chaberti | Bolivia | 1968 | |
| Trichomycteridae | Trichomycterus itacarambiensis | Brazil | 1996 | |
| Trichomycteridae | Trichomycterus rosablanca | Colombia | 2018 | |
| Trichomycteridae | Trichomycterus rubbioli | Brazil | 2012 | |
| Trichomycteridae | Trichomycterus sandovali | Colombia | 2006 | |
| Trichomycteridae | Trichomycterus santanderensis | Colombia | 2007 | |
| Trichomycteridae | Trichomycterus sketi | Colombia | 2010 | |
| Trichomycteridae | Trichomycterus spelaeus | Venezuela | 2001 | |
| Trichomycteridae | Trichomycterus uisae (trepador) | Colombia | 2008 | |
| Sternopygidae | Eigenmannia vicentespelaea | Brazil | 1996 | |
| Amblyopsidae | Amblyopsis hoosieri (Hoosier cavefish) | United States | 2014 | |
| Amblyopsidae | Amblyopsis rosae (Ozark cavefish) | United States | 1898 | |
| Amblyopsidae | Amblyopsis spelaea (northern cavefish) | United States | 1842 | |
| Amblyopsidae | Forbesichthys agassizii (spring cavefish) | United States | 1872 | Found belowground, but also nearby in aboveground waters during the night |
| Amblyopsidae | Speoplatyrhinus poulsoni (Alabama cavefish) | United States | 1974 | |
| Amblyopsidae | Typhlichthys subterraneus (southern cavefish) | United States | 1859 | Possibly a species complex and T. eigemanni may be a valid species |
| Bythitidae | Diancistrus typhlops | Indonesia | 2009 | |
| Bythitidae | Lucifuga dentata (toothed Cuban cusk-eel) | Cuba | 1858 | |
| Bythitidae | Lucifuga lucayana (Lucaya cave brotula) | Bahamas | 2006 | |
| Bythitidae | Lucifuga simile | Cuba | 1981 | |
| Bythitidae | Lucifuga spelaeotes (New Providence cusk-eel) | Bahamas | 1970 | |
| Bythitidae | Lucifuga subterranea (Cuban cusk-eel) | Cuba | 1858 | |
| Bythitidae | Lucifuga teresinarum | Cuba | 1988 | |
| Bythitidae | Ogilbia galapagosensis (Galapagos cuskeel) | Ecuador | 1965 | Arguably not a true cavefish, as places it inhabits also can be described as lagoon crevices |
| Bythitidae | Typhliasina pearsei (Mexican blind brotula) | Mexico | 1938 | |
| Poeciliidae | Poecilia mexicana (cave molly) | Mexico | 1863 | Species includes both aboveground and belowground forms (aboveground also in Central America) |
| Synbranchidae | Rakthamichthys digressus | India | 2002 | |
| Synbranchidae | Rakthamichthys indicus | India | 1961 | Originally described as Monopterus indicus by K. C. Eapen, but as this name was already taken by the Bombay swamp eel, it was redescribed as Monopterus eapeni in 1991. When the species was moved to the genus Rakthamichthys, the indicus specific epithet was revived. |
| Synbranchidae | Rakthamichthys roseni | India | 1998 | |
| Synbranchidae | Ophisternon candidum (blind cave eel) | Australia | 1962 | |
| Synbranchidae | Ophisternon infernale (blind swamp eel) | Mexico | 1938 | |
| Cottidae | C. bairdi—cognatus species complex (mottled sculpin/slimy sculpin) | United States | 1850/1836 | Aboveground forms relatively widespread in North America and Siberia, underground form only in Pennsylvania |
| Cottidae | Cottus carolinae (banded sculpin) | United States | 1861 | Aboveground forms relatively widespread in the United States, underground form only in West Virginia |
| Cottidae | Cottus specus (grotto sculpin) | United States | 2013 | Formerly included in C. carolinae |
| Butidae | Bostrychus microphthalmus | Indonesia | 2005 | The family Butidae was formerly considered a subfamily of Eleotridae |
| Butidae | Oxyeleotris caeca | Papua New Guinea | 1996 | The family Butidae was formerly considered a subfamily of Eleotridae |
| Butidae | Oxyeleotris colasi | Indonesia | 2013 | Has mistakenly been reported to occur in Papua New Guinea, but it is from Western New Guinea, the Indonesian part of the island. The family Butidae was formerly considered a subfamily of Eleotridae |
| Eleotridae | Caecieleotris morrisi (Oaxaca cave sleeper) | Mexico | 2016 | |
| Milyeringidae | Milyeringa brooksi | Australia | 2010 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Milyeringidae | Milyeringa justitia (Barrow cave gudgeon) | Australia | 2013 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Milyeringidae | Milyeringa veritas (blind gudgeon) | Australia | 1945 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Milyeringidae | Typhleotris madagascariensis | Madagascar | 1933 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Milyeringidae | Typhleotris mararybe | Madagascar | 2012 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Milyeringidae | Typhleotris pauliani | Madagascar | 1959 | The family Milyeringidae was formerly considered a subfamily of Eleotridae |
| Gobiidae | Caecogobius cryptophthalmus | Philippines | 1991 | |
| Gobiidae | Caecogobius personatus | Philippines | 2019 | |
| Gobiidae | Glossogobius ankaranensis | Madagascar | 1994 | |
| Gobiidae | Luciogobius albus | Japan | 1940 | |
| Gobiidae | Luciogobius pallidus | Japan | 1940 | |
| Aenigmachannidae | Aenigmachanna gollum (Gollum snakehead) | India | 2019 | One of two species in a unique fish family closely related to true snakeheads. Displays relatively few troglomorphisms despite living in underground aquifers, and thus could either be a recent arrival to the subterranean ecosystem or possibly a subtroglophile that periodically moves between the underground and surface. |
| Aenigmachannidae | Aenigmachanna mahabali | India | 2019 | One of two species in a unique fish family closely related to true snakeheads. Displays relatively few troglomorphisms despite living in underground aquifers, and thus could either be a recent arrival to the subterranean ecosystem or possibly a subtroglophile that periodically moves between the underground and surface. |

## Conservation

Although cavefish as a group are found throughout large parts of the world, many cavefish species have tiny ranges (often restricted to a single cave or cave system) and are seriously threatened. In 1996, more than 50 species were recognized as threatened by the IUCN and many, including several that are rare, have not been assessed at all. For example, the critically endangered Alabama cavefish is only found in the Key Cave and the entire population has been estimated at less than 100 individuals, while the critically endangered golden cave catfish only is found in the Aigamas cave in Namibia and has an estimated population of less than 400 individuals. The Haditha cavefish from Iraq and the Oaxaca cave sleeper from Mexico may already be extinct, as recent surveys have failed to find them. In some other cases, such as the Brazilian blind characid which went unrecorded by ichthyologists from 1962 to 2004, the apparent "rarity" was likely because of a lack of surveys in its range and habitat, as locals considered it relatively common until the early 1990s (more recently, this species appears to truly have declined significantly). Living in very stable environments, cavefish are likely more vulnerable to changes in the water (for example, temperature or oxygen) than fish of aboveground habitats which naturally experience greater variations. The main threats to cavefish are typically changes in the water level (mainly through water extraction or drought), habitat degradation and pollution, but in some cases introduced species and collection for the aquarium trade also present a threat. Cavefish often show little fear of humans and can sometimes be caught with the bare hands. Most cavefish lack natural predators, although larger cavefish may feed on smaller individuals, and cave-living crayfish, crabs, giant water bugs and spiders have been recorded feeding on a few species of cavefish.
Caves in some parts of the world have been protected, which can safeguard the cavefish. In a few cases such as the Omani blind cavefish (Oman garra), zoos have initiated breeding programs as a safeguard. In contrast to the rarer species, the cave form of the Mexican tetra is easily bred in captivity and widely available to aquarists. This is the most studied cavefish species and likely also the most studied cave organism overall. As of 2006, only six other cavefish species have been bred in captivity, typically by scientists.