Researchers rediscover a freshwater fish that hasn't been seen in nearly 50 years

Researchers rediscover a freshwater fish that hasn’t been seen in nearly 50 years
A Batman River loach, the species lost to science since 1974 was recently rediscovered in southeast Turkey. It is the first fish to be rediscovered on Shoal and Re:wild’s top 10 most wanted lost fishes list. Credit: Re:wild

Turkish ichthyologists have rediscovered populations of the critically endangered Batman River loach in two streams in southeast Turkey, the first time the tiny fish has been seen since 1974, and the first species rediscovered on Shoal and Re:wild's top 10 most wanted lost fishes list, which launched in June 2021.

"When I first heard about the Search for the Lost Fishes project, I was very happy," said Cüynet Kaya, associate professor with Recep Tayyip Erdogan University. "Moreover, two of the 10 most wanted fish species were distributed in my country. It is a very different feeling when you see naturalists from foreign countries caring about an endemic species in your country and making efforts to save it. As a freshwater fish taxonomist, I thought that I should do my best for this project, and fortunately our efforts resulted in finding the first lost endemic and critically endangered Batman River loach."

After learning about the Search for Lost Fishes, Kaya and Münevver Oral, a research fellow with Recep Tayyip Erdogan University, set out to search for the small yellow-and-brown striped fish which is the smallest loach species in the Middle East, and smaller than any loach species found in Europe. The tiny critter, growing up to 1.4 inches (or 36 millimeters) long, was once distributed around streams and tributaries of the Batman River, which is thought to take its name not from the caped-crusader, but from the nearby Bati Raman mountain.

Expedition teams have searched the river underneath the historic Malabadi bridge and the lower parts of the Batman River, where the fish was first discovered, many times in the decades since the Batman River loach's last sighting, without success. After analyzing possible locations where the Batman River loach could survive, Kaya and Oral instead focused their search on the Sarim Stream, which is upstream of the Batman Dam. In October and November 2021, the team visited the stream and other headwaters of the Batman River, which are shallow, rocky and fast-flowing, the preferred habitat of the fish.

Kaya and Oral searched the streams using tight-weave nets that prevented the Batman River loach from slipping through. They found 14 fish in the Sarim Stream and another nine in the Han Stream.

Kaya and Oral said the population of the loach seems steady, but they are concerned about the effects of pollution, drought, and , and stressed that further study is needed to get a clearer understanding of the species' total distribution.

"When we launched the Search for the Lost Fishes, we hoped that we would have the opportunity to celebrate days like this," said Mike Baltzer, executive director of Shoal. "There are so many lost and threatened fish and we are so happy that this little loach has been found, and hopefully we can now secure its future. This is the first species of Lost Fishes that has been rediscovered—hopefully the first of many."

Populations of the Batman River loach nosedived after the construction of the Batman Dam in Turkey between 1986 and 1999, leading some scientists to fear it may have become extinct. Construction of the Batman Dam may have caused populations of the species to fall and, when Kaya and Oral sampled areas downstream of the dam, where the species was recorded in 1974, they were unable to find any individuals. The species' habitat is now fragmented due to the dam, and the fish can no longer move downstream.

"We have searched for this for many years. It is obviously very rare, as it has not been found in the original locations that it was previously recorded," said Jörg Freyhof, Europe's leading ichthyologist and expert on these fishes, and who is co-authoring a research paper with Kaya about the rediscovery. "We even doubted that it existed. Cüneyt made massive efforts to finally confirm its existence. Its finding is a sign of hope, that this species has survived despite everything that has been done to kill the river."

Shoal and Re:wild launched the Search for Lost Fishes with in June 2021, in a bid to encourage people to look for species that have fallen off the radar, so that conservation programs can be put in place to bring them back from the brink of extinction.


Shoal is a global collaborative initiative to halt the extinction and recover populations of the most threatened freshwater species in the wild. Freshwater species are going extinct faster than their marine or terrestrial cousins, and almost one in three of those alive today could soon disappear, never to return. There is an urgent need for determined action, and Shoal is building a strong community of partners that will work together to give critical attention, escalate support, and accelerate and intensify the action that is required to stem the tide of extinction and recover endangered species populations throughout the Earth's freshwaters.

Shoal's Search for the Lost Fishes project highlights more than 300 freshwater that haven't been recorded in over a decade, but which are yet to be declared Extinct by the IUCN Red List. By promoting the , Shoal hopes that they will be rediscovered, allowing for robust conservation projects to be implemented to bring them back from the brink of extinction.

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