“Holy loach!” … “Batman loach returns” … “Tiny superhero fish rediscovered” … It was almost inevitable that the rediscovery of the Batman River loach in a stream in eastern Turkey would spawn a slew of comic book puns in headlines around the world. “Batman is a city and province in Turkey with the same name, and the name of the stream is Batman,” says Dr Cüneyt Kaya, associate professor at Recep Tayyip Erdoğan University. “For Turkish people, the name seems normal, but for foreigners, of course, people find it strange or funny.” The Batman River loach was thought to be extinct after the last confirmed sighting of the fish nearly 50 years ago, in 1974. But then Kaya and a colleague rediscovered the fish in October 2021. Kaya had been studying the fish of the Tigris River for more than a decade, but had failed to find signs of the fish. The Batman River loach is one of the smallest loach species in the world – the maximum known size is 3.6cm. “Perhaps that’s why it wasn’t easy to find,” says Kaya. “But when Shoal and Re:wild made a list of the Top 10 Most Wanted Lost Fishes, we led the project to find it.” The search was focused on an area of the Batman River, a tributary of the Tigris, upstream from the Batman dam, which was built between 1986 and 1999. But finding the tiny cylindrical yellow-and-brown striped fish, when others had failed, was down to luck, says Kaya’s colleague, Dr Münevver Oral, a geneticist and research fellow at the same university. “Cüneyt and I were at the beginning of a nine-day field trip in eastern Turkey,” says Oral. “The target of the trip was another small fish species, Turcinoemacheilus, which belongs to the same family (Nemacheilidae) as the Batman River loach, so we used a smaller mesh so the fish would not slip through. “With the seasonally lower level of water, it was our luck that the Batman River loach went into our net on the first day, after not being seen for 48 years,” Oral says. Kaya and Oral found Batman River loaches in two different streams: 14 in shallow, rocky, fast-flowing areas of the Sarım stream and nine in the Han stream. “When I saw it, I thought it might be another fish species,” says Kaya. “I took more samples. When I was sure this was the Batman River loach, I was very excited.” Since the loach was rediscovered, there have been some interesting findings. “The genetic analysis revealed the Batman River loach is Schistura chrysicristinae, not Paraschistura chrysicristinae, as we initially thought,” says Oral. “Schistura’s known distribution range is from Pakistan to China. But our molecular results proved Schistura exist 3,000km west from this, meaning the distribution range is much greater than was previously thought.” Since 2021, Kaya and Oral have returned to the same streams. “After the first discovery, we went back there and saw about 50 Batman River loaches,” says Kaya. “The population is doing well. But the stream is very small and the population restricted, so we need to clean up the river and protect the species. “There are two critical issues in the river: pollution, especially plastic pollution, and ‘ghost’ fishing, or illegal fishing. Abandoned or broken fishing nets get left behind, stuck in streams. “The best solution is to educate people, especially kids, so we’ve been in several high schools in the region to talk about microplastics and the effects of ghost fishing, and we’ve had some very positive results. “We also went to Ankara to speak about the loach with the General Directorate of Fisheries and Aquaculture. Soon, they will start to collect the rubbish, plastics and the ghost-fishing nets from the Han and Sarım streams. We’ve waited a long time for this.” Rediscovering lost species gives conservationists hope, not just for that species, but for protecting wider ecosystems, the two scientists say. “Removing the pollution and nets will benefit all the species in the river ecosystem, not just the Batman River loach,” says Kaya. “Maybe these streams also have more potential new species that are strictly endemic. I suspect there is one, or maybe even two new fish species there. We can’t name them yet but we’re working on the findings.”