lost fishes

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All around the world, freshwater fish face multiple stressors that have caused populations to plummet and, for all kinds of reasons, once discovered species have fallen off our radar. These Lost Fishes are species that have gone unseen for years – even decades – and are feared possibly extinct. In order to save these species, we first need to find them.

Working with Shoal, we have launched a freshwater fish-focused extension to our successful Search for Lost Species campaign. In collaboration with Shoal and the IUCN-SSC Freshwater Fish Specialist Group, we have compiled a list of more than 300 fish species that are currently missing to science.

annamite barb
Scientific Name: Hypsibarbus annamensisLast Seen: 1969 in VietnamYears Lost: 52Red List Status: Data Deficient

The species is only officially known from three individuals: one collected in 1936, and two collected in 1969 (without the location recorded). We're not sure why the species has vanished, but the location where the first individual was found was impacted in the 1970s by deforestation.

diyarbakir (batman river) loach
Scientific Name: Paraschistura chrysicristinaeLast Seen: 1974 in TurkeyYears Lost: 47Red List Status: Critically Endangered

Individuals were collected from the Batman and Ambar rivers on 10 May 1974 by Ali Demirsoy and Ali Kelle. Kelle completed the first detailed faunistic study on the fishes of Tigris in 1978 but did not list any new species, including Paraschistura chrysicristinae. Later, he contacted Teodor T. Nalbant who was an expert on loaches, who described the species in 1998.

The habitats in the localities it has previously been recorded appear to be of good quality, though the construction of the Batman Dam between 1986-1999 would likely have had negative impacts on the species.

The species is a dwarf loach, with a standard length of up to 36 mm.

duck-billed buntingi
Scientific Name: Adrianichthys kruytiLast Seen: 1983 in IndonesiaYears Lost: 37Red List Status: Critically Endangered

Local fishermen believe the Duck-billed Buntingi's decline it is related to the eruption of the nearby Colo Volcano in 1983. Invasive species have likely also played a part, and introduced diseases and parasites are also possible explanations. Overfishing has also likely caused numbers to plummet.

The fish grows up to 16 cm, though usually closer to 11cm.

spinach pipefish
Scientific Name: Microphis spinachioidesLast Seen: 1985 in Papua New GuineaYears Lost: 36Red List Status: Data Deficient

It’s unsurprising that so little is known about this species: The terrain on Papua New Guinea is extremely difficult to negotiate, distances are huge, roads are few and far between, and air travel is expensive and often non-existent to remote locations. Also, the holotype was stored in the Hamburg Museum, but was destroyed during World War II.

As a pipefish, it’s closely related to seahorses. Most species of pipefish are inhabitants of tropical and temperate seas, but a few species in the Indo-Australian Archipelago are largely restricted to freshwater.

Aside from their idiosyncratic looks, pipefishes display some extraordinary behavior: females deposit their eggs on the underside of the male’s trunk, or tail, where the male incubates them for several weeks either partly or fully concealed in a pouch.

The species is so poorly known that scientists aren’t really sure of its size, but it grows to at least 15cm and possibly up to 22cm.

mesopotamian barbel
Scientific Name: Luciobarbus subquincunciatusLast Seen: 2011Years Lost: 10Red List Status: Critically Endangered

This species, which is also known as the Leopard Barbel or Spot Barb, ranges from the Tigris-Euprhates river system in Eastern Turkey, Eastern Syria, Iran and Iraq. One individual was caught in 2011, the last time this fish was scientifically documented. The Mesopotamian Barbel was once abundant in certain locations but has declined rapidly over the past 30 years or more as the result of overfishing, habitat loss, eutrophication, dam constructions and water abstraction. The fish grows up to 60cm.

Syr Darya Shovelnose Sturgeon
Scientific Name: PSEUDOSCAPHIRHYNCHUS FEDTSCHENKOILast Seen: 1960S IN KAZAKHSTANYears Lost: ABOUT 60Red List Status: Critically Endangered

The striking Syr Darya Shovelnose Sturgeon is endemic to the Syr Darya River, and once found in Kazakhstan, Tajikistan and Uzbekistan. It is among the smallest sturgeon species in the world, growing only up to about one foot long. It was once found in the Aral Sea, but according to NASA, the Aral Sea shrunk by more than 60% between 1973 and 2000. The Aral Sea is now hypersaline and as a result, doesn’t contain any fish, aside from in a small reservoir. The river has also experienced large levels of water extraction, damming and agricultural pollution. The sturgeon has been listed in the Red Data Book of Kazakhstan since 1978 and has also been featured on stamps.

Although a Re:wild-supported expedition team from the Tennessee Aquarium, Eurasian Regional Association of Zoos and Aquariums, and Kazakhstan Fisheries Research and Production Center was not able to rediscover the species at the end of 2018, what they did find has spurred hope that they’ll succeed on future trips.


titicaca orestias
Scientific Name: Orestias cuvieriLast Seen: 1952Years Lost: 69Red List Status: Data Deficient

The Titicaca Orestias is the largest member of the pupfish genus Orestias and, despite its name, it is not the only Orestias fish from Lake Titicaca. Orestias cuvieri is thought to be as old as 5 million years and is specifically adapted to its closed lake environment.

In 1937, 500,000 trout eggs were sent to Lake Titicaca, irreversibly altering the native ecosystem. There has been severe competition from introduced trout, including lake trout, brown trout, and rainbow trout, as well from Argentinian silverside from the 1930s to the 1950s. Pollutants have contaminated the water and traces of metals, such as zinc and copper have been found in the tissues of fishes. In addition, runoff from fertilizers and pesticides used in agriculture has been extremely toxic to the fish.

haditha cavefish
Scientific Name: Caecocypris basimiLast Seen: 1983 in IraqYears Lost: 38Red List Status: Critically Endangered

The Haditha cavefish is known only from a subterranean system in a sinkhole at the Sheik Hadid shrine, near Haditha, Iraq. The only way to access the system is through a well approximately five meters below the shrine. A comprehensive survey of the site in 2012 did not find the species. Water abstraction from the well itself has lowered the groundwater level, which appears to be a major threat. It is also thought that reduced groundwater levels due to water abstraction and hydrological modifications caused by the construction of a large dam near the Euphrates may have negatively impacted the site.

itasy cichlid
Scientific Name: Ptychochromoides itasyLast Seen: 2010 in MadagascarYears Lost: 11Red List Status: Critically Endangered

Until it was rediscovered in a pond at a tributary of the Tsiribihina River in late 2010, the Itasy Cichlid was only known from Lake Itasy, where it had last been seen in the 1970s. It was considered Extinct until the rediscovery.

Its coloration is jet black and the local name for the fish is ‘trondro mainty’, which translates to ‘blackfish’. 

It differs from its close relatives in having a pronounced occipital hump, even in small fishes that aren’t yet sexually mature, and in females.

The fish's population has dropped as a result of a decline in water quality due to human mediated disturbances, specifically unregulated overfishing and the introduction of invasive species into the Lake Itasy basin, which led to the swift decline of native fishes throughout the region.

fat catfish
Scientific Name: Rhyzosomichthys totaeLast Seen: 1957 in ColombiaYears Lost: 64Red List Status: Critically Endangered

The Fat Catfish possesses remarkable rings of extensive adipose tissues surrounding the body – the only freshwater catfish in the world that has fatty rings of this kind. It’s so greasy that it’s sometimes referred to as the ‘greasefish’, and locals to Lake Tota used to impale it on sticks, set it alight, and use it as a torch. Only 10 individuals have been recorded.

In 1936, 100,000 rainbow trout eggs, imported from North America, were released into the lake. Cecil Miles – the man who first described the species – claimed this would cause the extinction of the Fat Catfish. In 1990, Colombian ichthyologist José Iván Mojica claimed the trout and the fat catfish lived in different parts of the lake, lending dispute to Miles’ claim.


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