Endangered Species 2010 Series main post.
Fish are, generally speaking, ectothermic (cold-blooded) aquatic vertebrates with fins and scales. The various species we refer to as ‘fish’ are classified according to one of three taxonomic groups: the Actinopterygii, Sarcopterygii and Chondrichthes (the lamprey and hagfish are belong to the classes Petromyzontiforma and Myxini respectively. They may not strictly speaking be true fish). The Actinpoterygii are the ray-finned fish; their fins are formed from skin supported by bony struts; the Sarcopterygii are the lobe-finned fish whose fins are, as you may expect, substantial and fleshy (the first tetrapods evolved from sarcopterygian ancestors); the Chondrichthes are cartilaginous fish such as sharks, skates and rays.
This list focuses on the largest of these groups, the Actinopterygii. There are around 24,000 known species, representing over 95% of fish and around half of the known vertebrate fauna. Of these 24,000 species, approximately 23,000 belong to the infraclass Teleostei which includes eels, salmon, cichlids, goldfish and anglerfish. Ray-finned fish can be found in almost every aquatic habitat. Despite this capacity for adaptation and diversification, many species are sensitive to disturbance and relatively minor changes in water quality, thus, habitat destruction, pollution, collection for international trade and other anthropogenic effects are having severe impacts on many species.
 Jonna, R. (2010). Actinopterygii. Encyclopedia of Life. [online]
 Waggoner, B. (2006). Introduction to the Actinopterygii. Regents of the University of California. [online]
Dwarf Sturgeon (Pseudoscaphirhynchus hermanni)
The dwarf sturgeon is a relative of the European sturgeon (Huso huso) from which we derive beluga caviar and which is itself critically endangered. The dwarf sturgeon is endemic to the middle of the Amu Darya river of Turkmenistan and Uzbekistan where it is believed to occur in a stretch of less than 500km.Little is known regarding population size or viability. The species’ presence on the Red List is due to the impacts of pollution, habitat destruction and poaching which may have reduced the population by 80% in 3 generations.
 Mugue, N. 2009. Pseudoscaphirhynchus hermanni. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Pseudoscaphirhynchus hermanni. FishBase. [online]
Chao Phraya giant catfish (Pangasius sanitwongsei)
This giant of the Mekon delta, China, is threatened by harvesting – it is a popular and important food fish – and habitat alteration. The construction of the first dams built on the Mekong, one of the world’s longest rivers, and its tributaries began in the late 1980′s. The ecological havoc wreaked by these dams has emperiled many species. Once relatively abundant, P. sanitwongsei now appears to persist in two sub-populations either side of Khone Falls.
 Jenkins, A., Kullander, F.F. & Tan, H.H. 2007. Pangasius sanitwongsei. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Pangasius sanitwongsei. FishBase. [online]
 Mekong River Commission (N/K). Key Mekong fish species – migration paths: Pangasius sanitwongsei. [online]
Image © Ingo Seidel
Kezenoi-am trout (Salmo ezenami)
S. ezenami is endemic to Lake Kenzio-am, a small (2.4km^2) water-body in northern Caucasus, Russia. The trout was the only fish present in the lake and tributaries until the introduction of the Caspian gudgeon (Gobio holurus) and the European chub (Squalius cephalus). The latter species is particularly problematic as it feeds on the fry of S. ezenami. Specific information is scarce though it does appear that the species has been successfully introduced to Lake Mochokh, Daghestan.
 Freyhof, J. & Kottelat, M. 2008. Salmo ezenami. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Salmo ezenami . FishBase. [online]
 N.G.Bogutskaya, A.M.Naseka (2002). Freshwater Fishes of Russia. Zoological Institute RAS. [online]
Image depicts Salmo pelagonicus.
Dwarf loach (Yasuhikotakia sidthimunki)
There is little information available on the wild status of this species. Endemic to the Chao Phraya and Mekong basins of Cambodia, Laos and Thailand, it is a popular aquarium fish which appears to breed well in captivity (though exploitation of wild stocks may continue). Habitat alteration may also be a threat.
 Kottelat, M. 1996. Yasuhikotakia sidthimunki. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2
 Froese, R., Pauly, D. (eds.). (2010). Yasuhikotakia sidthimunki. FishBase. [online]
Image © Bill Harada
Red-finned blue-eye (Scaturiginichthys vermeilipinnis)
The red-finned blue-eye is endemic to Australia where it inhabits five freshwater springs at Edgbaston Springs, Queensland. It is the smallest of Australia’s freshwater fish species with a length of just 30mm. The size and temperature of the springs are subject to seasonal flux and it is thought the blue-eye uses seasonal floods as a means of migration and dispersal. It is thought that there are at most a few thousand individuals remaining.
 Wager, R. 1996. Scaturiginichthys vermeilipinnis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2
 Froese, R., Pauly, D. (eds.). (2010). Scaturiginichthys vermeilipinnis. FishBase. [online]
Image © Gunther Schmieda
Romanian darter (Romanichthys valsanicola)
R. valsanicola was previously found in fast-flowing waters of the River Arges, Romania, and its associated tributaries of Valsan and Raul Doamnei. The species disappeared from the Arges due to the construction of a reservoir in 1965. It is now restricted to 1km of the Vaslan river where it is threatened by overfishing, pollution, stone extraction and upriver damming activities.
 Freyhof, J. & Kottelat, M. 2008. Romanichthys valsanicola. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Romanichthys valsanicola. FishBase. [online]
Lake Victoria deepwater catfish (Xenoclarias eupogon)
X. eupogon is a catfish of the family Clariidae, a group of elongated freshwater species some of which are able to breathe air and migrate across land between bodies of water. This particular species is endemic to Lake Victoria, Kenya where it inhabits the deeper parts of the lake. Like many other species in Lake Victoria, X. eupogon is thought to have been subject to intense predation by introduced Nile Perch (Lates niloticus). No specimens have been recorded since 1997 ; the species may be extinct.
 Hanssens, M. & Snoeks, J. 2006. Xenoclarias eupogon. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Xenoclarias eupogon. FishBase. [online]
 Goudswaard, K., Witte, F. (1997). The catfish fauna of Lake Victoria after the Nile perch upsurge. Environ Biol Fish. 49: 21-43. [available online]
Monterrey platyfish (Xiphophorus couchianus)
This species is a live-bearer (gives birth to live young) endemic to Monterrey, Mexico. It is a popular aquarium and biological research species. There are fewer than 250 wild individuals remaining, spread between several fragmented sub-populations.
 Contreras-Balderas, S. & Almada-Villela, P. 1996. Xiphophorus couchianus. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Xiphophorus couchianus. FishBase. [online]
Image © K Nilsson
T. turskyi is restricted to an area of occupancy of less than 10km^2 in the Cikola river, Croatia. The species was thought extinct until a population was discovered in 2002. The dominant threats are water extraction, pollution and drought.
Note: The species was reclassified from Leuciscus to Telestes in 2004.
 Crivelli, A.J. 2006. Telestes turskyi. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Telestes turskyi. FishBase. [online]
Image © Kelvin K. P. Lim
Chinese Paddlefish (Psephurus gladius)
The Chinese paddlefish (the ‘giant panda of the rivers’) is one of two extant paddlefish species and is one of the largest freshwater fish in the world with a length of up to (and probably over) 7 metres. The species inhabits the Yangtze River, China, where the Gezhouba Dam has fragmented the habitat, preventing adults from reaching the upper parts of the river to spawn. The species has been subject to intense fishing and its young are easily netted due to their schooling habits. It has not been possible to breed the species in captivity and it is considered to be on the brink of extinction.
 Qiwei, W. 2009. Psephurus gladius. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2
 Froese, R., Pauly, D. (eds.). (2010). Psephurus gladius. FishBase. [online]
 Wu, X.-C. (2005). The loss of genetic diversity in the Chinese paddlefish (Psephurus gladius Martens) as revealed by DNA fingerprinting. J Genet. 84(3):323-327. [available online]
Gwyniad (Coregonus pennantii)
C. pennanti is a whitefish belonging to the Salmonidae (the salmon family). It is endemic to Lake Tegid, a 4km^2 waterbody in Snowdonia, Wales and may now be established in Llyn Arenig through relocation efforts. Primary threats are water degredation, seasonal hypoxia at depth and predation on eggs, fry and spawning adults by introduced ruffe (Gymnocephalus cernuus).
 Freyhof, J. & Kottelat, M. 2008. Coregonus pennantii. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Coregonus pennantii. FishBase. [online]
Atlantic goliath grouper (Epinephelus itajara)
E. itajara is a large (2.5m in length; 350kg+) marine grouper. Mature adults are apex predators and thus exist at low densities on reefs where they hunt other fish and invertebrates. The species is a popular food item. Overfishing, a slow growth rate and loss of suitable juvenile habitat saw catches decline significantly; harvesting has been prohibited across some of the species range since 1990 (USA; Brazil – 2002; US Caribbean – 1993. See the IUCN page for the full range). Current population levels are unknown, though in unprotected areas numbers are probably still in decline. The Gulf of Meixco population was noted as being in recovery in 2006; it is unknown whether the recent Deepwater Horizon disaster has significantly affected this population.
 Chan Tak-Chuen, T. & Padovani Ferrera, B. 2006. Epinephelus itajara. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Epinephelus itajara. FishBase. [online]
 Robertson, R. (N/K). Epinephelus itajara (Lichtenstein, 1822). Encyclopedia of Life. [online]
Image © Paul Humann
Alabama cavefish (Speoplatyrhinus poulsoni)
S. poulsoni may be one of the rarest freshwater fish in the world. It is known from a single underground cave system (Key Cave, Alabama) where it migrates between pools during seasonal floods. Though deep pools are known within the cave system, no specimens have been identified therein. The fish are almost devoid of pigment and are entirely eyeless, relying on sensory papillae, neuromasts (‘tactile sensory organs’) and an exaggerated lateral line system for navigation and foraging. It is thought that there are 100 individuals within the cave system. They are threatened by groundwater pollution and a decline in the numbers of cave bats whose guano nutrifies the pools.
 Gimenez Dixon, M. 1996. Speoplatyrhinus poulsoni. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Speoplatyrhinus poulsoni. FishBase. [online]
 Moore, D., Wehrly, K. (2006). Speoplatyrhinus poulsoni. Animal Diversity Web. [online]
 Cooper, J. E., Kuehne, R. A. (1974). Speoplatyrhinus poulsoni, a new genus and species of subterranean fish from Alabama. Copeia. 2:286-493.
Image © Dante Fenolio
Cave catfish (Clarias cavernicola)
C. cavernicola is known from a single pool (18m x 2.5m; 30 – 52ft deep) in the Aigamas Cave, Namibia, where it inhabits shallow water shelves. It is a sightless species whose population size is unknown. Primary threats are collection for the aquarium trade and groundwater extraction.
 Bills, R. 2007. Clarias cavernicola. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Clarias cavernicola. FishBase. [online]
Image © Charles Maxwell
Duck-billed buntingi (Adrianichthys kruyti)
The duck-billed buntungi is found only in Lake Poso, Sulawesi, Indonesia. The species is classically threatened by exotic species, overfishing and pollution. However, the species may now be extinct in the wild.
 Kottelat, M. 1996. Adrianichthys kruyti. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2.
 Froese, R., Pauly, D. (eds.). (2010). Adrianichthys kruyti. FishBase. [online]