Clarias cavernicola

Trewavas 1936

Clarias cavernicola
Redrawn by Rhian Kendall from Trewavas (1936)


Historical notes

This species may have first been discovered between 1917 and 1919 by the geologists Jaeger and Waibel (1921) (see Skelton 1990, Berti and Messana 2010).

The first specimens were obtained by Karl Jordan in 1933 and reported back, by letter1, to Jordan’s employer, Walter Rothschild. The following paragraph is by Kristin Johnson regarding this letter:

Their most interesting find was a semi-transparent pinkish Silurid, 6 inches long with a minute eye, which they had found in a cave 250 feet below the surface of the soil. “It was quite an undertaking to get to the crevice which gave access to the water,” he reported, “that had receded out of sight; we were 7 Europeans and 3 blacks, and with the help of ropes and ladders we got what I wanted.” (Jordan 1933). Details from Kristin Johnson pers. comm. July 2020.

Johnson (2004, 2012), gives his age as 72 and the year of the expedition as 1933:

"Perhaps Rothschild recognized the debt he owed, however, for in the winter of 1933 he allowed Jordan to go on his first collecting trip outside Europe to collect lepidoptera and fleas in Southwest Africa. Jordan was seventy-two years old.” (Johnson 2004:293, Johnson 2012:234).

The date of 1933 is also mentioned in Jordan's own Commentary:

"I was reminded of this queer optimism when I gazed early in October 1933 for the first time on Walfish Bay and its hinterland." (Jordan 1936:17).

Bert and Messana (2010), in their review of African subterranean fishes, give the right year, 1933.

However, there are other sources in the literature which give the wrong year for the expedition and the wrong age for Jordan when he carried it out.

Jacobs et al. (2019, 2019, 2020) record that Jordan found the species in 1921.

Rothschild (1955), in a biography of Jordan says:

" the age of seventy-four a major and very successful expedition of seven months’ duration to South-West Africa and Angola." (Rothschild 1955:7).

Riley (1959), in his obituary says:

"At the age of seventy-four, Jordan made his first really ambitious collecting expedition, to South West Africa" (Riley 1959). This is probably a direct copy from Rothschilds biography. See also Riley (1960).

An age of 74 (he was born in 1861, Rothschild 1955) would make the year 1935 which is wrong.

The type specimens were registered in 1935 (Ferraris 2007:141).

1 Karl Jordan to Walter Rothschild, November 27, 1933. DF306 Folder 3. Natural History Museum (London)







Lectotype: BMNH 1935.3.20:174 145mm TL

Paralectotypes: BMNH 1935.3.20:175‑178 118mm ‑ 147mm TL.

These types were assigned by Teugels (1986:134‑137) and are taken from the syntype series of Trewavas (1936). Trewavas records that the species was described from six animals but this is a mistake. The BMNH collection contains only five type specimens (G. S. Proudlove personal observation) and they are the ones used by Teugels.


Known only from the type locality: Aigamas (or Aigumas) Cave, north of Otavi, west of Grootfontein, Namibia (19o26’30”S, 17o17’26”E). A very large lake in Dragons Breath Cave in the same area has been examined by divers but no sign of this species was seen (Maxwell 1988; Irish 1992). There is a film available on the internet which suggests that this species is known from Dragons Breath Cave but this is erroneous and should be diregarded (Gerald Favre and Alessio Fileccia pers. comm.). Despite this error it is worth watching the film for the last few moments as the fishes are beautifully portrayed. See below for surveys of Aigamas Cave, in plan and in section, with cave fishes shown in their usual place in the cave. If you click on the surveys below they will be enlarged.


The pool is in total darkness and is 18m by 2.5m in area, its depth is 30-52m although the fishes appear to live over shelves in shallow water up to 15m in depth (Jacobs et al. 2019, 2019, 2020). The water temperature is 27oC. The food supply consists of insects associated with bat and baboon guano and insects from carcases of dead animals (Skelton 1990a,1990b,1990c; Bruton 1995). The cave is inhabited by a large colony of the bat Hipposideros commersoni (Churchill, Draper and Marais 1997). The lake is also home to an endemic troglomorphic Isopod Namibianira aigamasensis Kensley 1995. The cave is described in detail by Sefton et al. (1986).


Trewavas (1936) suggested that the species was related to Clarias alluaudi Boulenger 1906, C. submarginatus Peters 1882, and C. dumerilii Steindachner 1866. After a very thorough study of all of the African species in the genus Teugels (1986) placed C. cavernicola in the subgenus Anguilloclarias together with the first two species named above. Also related to C. cavernicola are C. theodorae Weber, 1897 and C. nigromarmoratus Poll, 1967. The former of these two is particularly interesting as its range, in the Cunene and Okavango drainage basins, is adjacent to the Aigamas Cave, the home of C. cavernicola. C. dumerilii is not closely related as it differs in several important subgeneric characters.

Diogo et al. (2003), also de Pinna (1993) and de Pinna (1998), have suggested, on morphological grounds, that the most basal member of the Family Clariidae is Horaglanis, and that the next most basal is Uegitglanis.

Biological Notes

Jacobs et al. (2019, 2019, 2020), with cave-diving colleagues, carried out two surveys of the lake in Aigamas cave to determine the nature of the fish population and its habitat. These were part of a baseline study of the critically endangered fish at its only know site. A visual census in February 2019 revealed that there were around 115 fishes in the lake and that the great majority were living in the upper 3m of water (the lake is at least 40m deep). A second census in May 2019 counted only about 40 individuals. During the February studies 10 animals were measured and the mean total length was 104mm (range 42mm-153mm). The difference in numbers sighted in February and May strongly suggests that the fishes have some migratory behaviour. This idea received some support by the fact that during these studies two further pools containing fishes were found in a close by cave formed on the same fault as Aigamas Cave. Thought not proven it is very likely that the two caves are part of the same hydrological system and the fishes seen in the original pool, and the new ones, are the same population. The new pools contained about 60 and 13 fishes respectively.  

Conservation Status

TLO [CR B1ab(iii)+2ab(iii):3.1:2007]

Bills, R. 2007. Clarias cavernicola. The IUCN Red List of Threatened Species 2007: Downloaded on 07 July 2017).

E (Miller 1977)

E (IUCN 1988)

E (IUCN 1990)

E (IUCN 1993)

CR B1+2c,E (IUCN 1996, 2000)

Endangered (Skelton 1990a,1990b,1990c).

The lake in Aigamas Cave has been used as a water supply in an otherwise very dry area. Pumping of water has reduced the depth of the lake from 70m to 50m since 1921 (Skelton 1990a,1990b,1990c, Bruton 1995). The animals appear to congregate above an underwater shelf  where they presumably obtain food from the bat colonies above them. This shelf is in danger of being exposed by the reducing water level. It is probably safe to say that this is one of the most endangered fishes in the world. During a dive in the lake in Aigamas Cave divers reported seeing hundreds of individuals (Speleofilms, Le Souffle du Dragon, Gerald Favre, no date). A population survey in 2019 recorded a maximum of 119 individual fishes (Jacobs et al. 2019).

This species is found in Ecoregion 79 (Karstveld Sink Holes) of Thieme et al. (2005). This is an area of subterranean and spring systems which is regionally outstanding faunistically, with a conservation status of endangered and a priority class of 4 (Skelton 2005).

Museum Holdings

Trewavas (1936) records that there were 12 specimens in addition to the type series but the BMNH collection contains only ten specimens from that period:

BMNH 1935.3.20:179‑188

Also BMNH 1971.8.10:1‑2, KMMA 74‑21‑P‑16‑17, ZSMH 6112 (Teugels 1986:134‑137). There are three specimens in the Department of Ichthyology, Rhodes University, South Africa (Jubb 1958). AMG/P 2679 (Skelton and Teugels 1991).

Key References

Note: Some marvellous film of this animal can be seen in the Speleofilm’s film: Le Souffle du Dragon (Speleofilms, Gerald Favre).

Jaeger, F. and Waibel, L. Book 1921 Beitrage zur Landschaften des nordlichen Sudwestafrika - Band 2. Landschaften des nordlichen Sudwestafrika
Jordan, K. Personal Communication 1933 Letter from Karl Jordan to Walter Rothschild, November 27, 1933. DF306 Folder 3. Natural History Museum (London)
Trewavas, E. Journal Article 1936 Dr Karl Jordans expedition to South West Africa and Angola: the freshwater fishes
Jordan, K. Journal Article 1936 Dr Karl Jordans expedition to South West Africa and Angola. Narrative
Rothschild, M. Journal Article 1955 Karl Jordan - A biography
Jubb, R. A. Journal Article 1958 A cave-dwelling cat-fish Clarias cavernicola Trewavas 1936, in South-West Africa
Riley, N.D. Journal Article 1959 Dr Karl Jordan FRA [obituary]
Graham, R. Journal Article 1959 [Note on] Jubb, R.A. A cave-dwelling catfish Clarais cavernlcola Trewavas 1936, in South West Africa.
Riley, N.D. Journal Article 1960 Heinrich Ernst Karl Jordan 1861-1959
Jubb, R. A. Book 1967 Freshwater fishes of Southern Africa
Gow, C. Journal Article 1968 Aigamas Cave
Bok, A. Thesis 1968 [The eyes, brain and sense organs of Clarias cavernicola]
Jubb, R. A. Journal Article 1969 Fishes of the dolomitic limestone caves and sinkholes of southern Africa
Hennig, H. Journal Article 1971 Note on the blind catfish Clarias cavernicola
Von Wrede, P. Journal Article 1977 Zusammenfassung der Bericht nber den blinde hoehlenfisch Clarias cavernicola Trewavas 1936
Von Wrede, P. Journal Article 1977 Zur kenntnis der Nahrungsquelle des hoehlenfisches Clarias cavernicola Trewavas 1936
Skelton, P. H. Journal Article 1977 South African Red Data Book. Fishes
Hennig, H. Journal Article 1977 Note on the blind catfish Clarias cavernicola
Miller, R. R. Book 1977 Red Data Book, Volume 4, Freshwater fishes
Scheide, P. Journal Article 1977 Cave-dwelling catfish
Teugels, G. G. Journal Article 1982 Preliminary data of a systematic outline of the African species of the the genus Clarias (Pisces, Clariidae)
Teugels, G.G. Journal Article 1982 A systematic outline of the African species of the the genus Clarias (Pisces, Clariidae) with an annotated bibliography
Penrith, M Journal Article 1985 Blind barbel
Teugels, G.G. Journal Article 1986 A systematic revision of the African species of the genus Clarias (Pisces, Clariidae)
Sefton, M. Journal Article 1986 Aigamas
Sefton, M., Martini, J. and Ellis, R. Journal Article 1986 Cave descriptions
Skelton, P. H. Journal Article 1987 Cave Catfish / Spelonk-barber
Skelton, P. Journal Article 1987 An expedition to the caves and sink holes of South West Africa, Namibia
Penney, A.J. and Maxwell, C.D. Journal Article 1988 Johan's Cave: a new cave on Aigamas Farm
Maxwell, C. Journal Article 1988 Underwater in Dragons Breath Cave
Penney, A.J. Journal Article 1988 The aquatic fauna of Dragon's Breath lake
Penney, A.J. Journal Article 1988 Notes on the collection of blind cave catfish from Aigamas Cave during Swex '87
Skelton, P. H. Journal Article 1989 Gems of a different kind
Skelton, P. H. Journal Article 1990 The conservation and status of threatened fishes in southern Africa
Skelton, P. H. Journal Article 1990 The status of fishes from the sinkholes and caves in Namibia
Skelton, P. H. Journal Article 1990 The status of fishes from sinkholes and caves in Namibia
Irish, J Journal Article 1991 Cave investigations in Namibia. 1. biospeleology, ecology, and conservation of Dragon's Breath Cave
Irish, J Journal Article 1991 Conservation aspects of karst waters in Namibia
Skelton, P. H. and Teugels, G. G. Journal Article 1991 A review of the Clariid catfishes (Siluroidei, Clariidae) occuring in southern Africa
de Pinna, M.C.C. Thesis 1993 Higher-levelphylogeny of Siluriformes,with a new classication of the order (Teleostei, Ostariophysi).
Kensley, B. Journal Article 1995 A new genus of aquatic cave-dwelling isopod from Namibia (Crustacea: Isopoda: Asellota)
Bruton, M. Journal Article 1995 Threatened fishes of the world: Clarias cavernicola Trewavas,1936 (Clariidae)
Marais, E. and Irish, J. Journal Article 1997 Cave investigations in Namibia, IV. Aikab hemicenote, and other karst phenomina in the Etosha national Park
Churchill, S., Draper, R. and Marais, E. Journal Article 1997 Cave utilisation by Namibian bats: population, microclimate and roost selection
Barnard, P. Book 1998 Biological diversity in Namibia
Adriaens, D. Thesis 1998 On how a larva becomes an adult catfish a functional morphological approach to the cranial ontogeny of the African catfish, Clarias gariepinus (Siluriformes, Clariidae)
Adriaens, D. and Verraes, W. Journal Article 1998 Ontogeny of the osteocranium in the African catfish, Clarias gariepinus Burchell (1822) (Siluriformes: Clariidae): Ossification sequence as a response to functional demands
Curtis, B., Roberts, K.S., Griffin, M., Bethune, S., Hay, C.J. and Kolberg, H. Journal Article 1998 Species richness and conservation of Namibian freshwater macro-invertebrates, fish and amphibians
Davis, B. and Day, J. Book 1998 Vanishing waters
de Pinna, M.C.C. Book Section 1998 Phylogenetic relationships of Neotropical Siluriformes (Teleostei: Ostariophysi): Historical overview and synthesis of hypotheses
Cabuy, E., Adriaens, D., Verraes, W. and Teugels, G.G. Journal Article 1999 Comparative study on the cranial morphology of Gymnallabes typus (Siluriformes: Clariidae) and their less anguilliform relatives, Clariallabes melas and Clarias gariepinus
Devaere, S., Adriaens, D., Verraes, W. and Teugels, G.G. Journal Article 2001 Cranial morphology of the anguilliform clariid Channallabes (Gunther 1873) (Teleostei: Siluriformes) are adaptations related to powerful biting?
Irish, J., Marais, E., Juberthie, C. and Decu, V. Book Section 2001 Namibia
Teugels, G.G. and Adriaens, D. Book Section 2003 Taxonomy and phylogeny of Clariidae - an overview
Diogo, R., Chardon, M. and Vandewalle, P. Journal Article 2003 On the osteology and myology of the cephalic region and pectoral girdle of Heteropneustes fossilis (Siluriformes: Heteropneustidae), with comments on the phylogenetic relationships between Heteropneustes and clariid fishes
De Schepper, N; Adriaens, D; Teugels, GG; et al. Journal Article 2004 Intraspecific variation in the postcranial skeleton morphology in African clariids: a case study of extreme phenotypic plasticity
Johnson, K. Thesis 2004 Karl Jordan: A life in systematics
Thieme, M.L., Abell, R., Stiassny, M.L.J.,Skelton, P., Lehner, B., Teugels, G., Dinerstein, E., Kamdem-Toham, A., Burgess, B., and Olson, D. Book 2005 Freshwater ecoregions of Africa and Madagascar. A conservation assessment
Scott, L. Book Section 2005 Ecoregion 79. Karstveld sinkholes
Agnese, J.F. and Teugels, G. Journal Article 2005 Insight into the phylogeny of African Clariidae (Teleostei, Siluriformes); Implications for their body shape evolution, biogeography, and taxonomy
Diogo, R. Book 2005 Morphological evolution, aptations, homoplasies, constraints and evolutionary trends. Catfishes as a case study on general phylogeny and macroevolution
Jansen, G., Devaere, S., Weekers, P.H.H. and Adriaens, D. Journal Article 2006 Phylogenetic relationships and divergence time estimate of African anguilliform catfish (Siluriformes: Clariidae) inferred from ribosomal gene and spacer sequences
Devaere, S., Jansen, G., Adriaens, D. and Weekers, P. Journal Article 2007 Phylogeny of the African representatives of the catfish family Clariidae (Teleostei, Siluriformes) based on a combined analysis: independent evolution towards anguilliformity
Darwall, W.R.T., Smith, K.G., Tweddle, D. and Skelton, P. Book 2009 The status and distribution of freshwater biodiversity in southern Africa
Darwall, W.R.T., Smith, K.G., Allen, D.J., Holland, R.A, Harrison, I.J., and Brooks, E.G.E. Book 2011 The diversity of life in African freshwaters: Under water, under threat. An analysis of the status and distribution of freshwater species throughout mainland Africa
Brooks, E.G.E., Allen, D.J. and Darwall, W.R.T. Book 2011 The status and distribution of freshwater diversity in central Africa
Johnson, K. Book 2012 Ordering life. Karl Jordan and the naturalist tradition
Fileccia, A. Journal Article 2012 Namgrows 2011, spedizione speleologica euro Africain in Namibia
Fileccia, A Conference Paper 2012 NAMGROWS. Namibian groundwater systems. Euro African joint cave expedition (A research project on karst aquifers in nothern Namibia)
Constant, P. Journal Article 2014 Namibian sinkholes. Exploring the magic triangle
Laumanns, M. Journal Article 2017 Atlas of the Great caves and the karst of Africa. Volume 2. Malawi to Zimbabwe and general references
Jacobs, F.J., Hay, C.H., Jacobs, P.G. and Næsje, T.F. Report 2019 A baseline study of the critically endangered cave-dwelling catfish (Clarias cavernicola)
Jacobs, F.J. and Hay, C.J. Journal Article 2019 Who needs eyes?
Jacobs, F.J., Hay, C.H, Jacobs, P.G. and Næsje, T.F. Report 2019 Preliminary technical report: A baseline study of the critically endangered cave-dwelling catfish Clarias cavernicola. Report no. MFMR-PRFR1-2019-04-30
Jacobs, F.J., Jacobs, P.G., Hay, C.J. and Naesje, T.F. Journal Article 2021 Status update of the endemic and critically endangered cave catfish Clarias cavernicola Trewavas 1936, from the Aigamas Cave system, Namibia
Skelton, P.H. Journal Article 2023 Fishes of the highlands and escarpments of Angola and Namibia
de Matos, D., Zastrow, J., Val, A. and Mendelsohn, J.M. Journal Article 2023 Caves and their fauna in the highlands and escarpments of Angola and Namibia
Aigamas Cave in section. Survey drawn by Alessio Fileccia and used with permission
Aigamas cave in plan. Survey drawn by Alessio Fileccia and used with permission.