‘Europe’s rarest fish’ numbers spawn hopes for species’ survival

‘Europe’s rarest fish’ numbers spawn hopes for species’ survival

  • The asprete, a rare freshwater fish found in Romania, was once considered extinct after dam construction destroyed much of its habitat.
  • The fish’s existence was confirmed by surveys conducted in the last 50 years but only a few were thought to survive in Romania’s Vâlsan River. In 2020, an official estimate suggested only 7 to 10 individuals remained.
  • However, a 2022 survey expedition found 58 specimens across a 15-kilometer (9.3-mile) stretch of the river, raising hopes that the species could be saved from extinction.
  • Experts say conservation efforts, as well as more robust survey attempts, led to the higher population count.

The asprete, a ray-finned freshwater fish species that lives only in Romania, has long captured Mircea Marginean’s imagination. He remembers hearing about the species in 2011, when he was a university student.

“I remember [my professor] saying that this is one of the most endangered freshwater fish species in Europe and probably in the world, and we don’t know exactly how many there are,” Marginean, who is now a biologist for the conservation organization Fauna & Flora International, tells Mongabay. “He was saying [there were] about 8 to 15, and I remember thinking I would be so happy to get the chance to work on fish species conservation.”

In October, Marginean got to go on a survey expedition to search for the elusive species. He and colleagues surveyed 41 sites in three rivers but found the species only in the Vâlsan River. Across a 15-kilometer (9.3-mile) stretch of the river, they identified 58 individuals.

“The best thing is that we still found it, and we managed to find more than we expected,” Marginean says. “I didn’t expect to find 58 individuals — I would have been so happy to have found 20.”

On a recent survey expedition, scientists identified 58 asprete fish in the Vâlsan River in Romania. Image by Alex Găvan.

First discovered in 1956, the asprete (Romanichthys valsanicola) occupies a genus of its own and has no close relatives. Some experts also believe the asprete has lived on Earth for up to 65 million years, earning the fish a reputation as a “living fossil.” The fish is a nocturnal species that lives on the river bottom, usually under rocks, making it hard to detect.

In the 1960s, Romania built several hydroelectric dams upstream from known asprete habitats in the Argeș, Vâlsan and Doamnei rivers. Marginean says the building of dams resulted in the removal of sand and stones from the riverbed and the drying up of water. Afterward, scientists could no longer find the asprete in the Argeș and Doamnei rivers. Some even wondered if the species as a whole had gone extinct.

But between the 1970s and early 2000s, fishers and scientists found the fish in the Vâlsan River — but only a handful at a time. In 2020, the Romanian ministry of the environment, water and forests estimated that there were 7 to 10 individuals left in the Vâlsan, leading some to refer to the asprete as “Europe’s rarest fish.”

In the early 2000s, conservationists working with an EU-funded LIFE Programme project helped reinstate some of the river flow of the Vâlsan River. Then in 2019, the Alex Găvan Foundation launched a project to further revitalize the river to protect the asprete, which is listed as a critically endangered species by the International Union for Conservation of Nature.

Ovidiu Stan, co-manager of the Alex Găvan Foundation, says there are currently four barriers in the Vâlsan River that cut the rivers into fragments.

“[The barriers] are not very big, but they endanger the current habitat,” Stan tells Mongabay in an email. “We have started the first studies to find the best ways to remove these barriers or if necessary, the construction of fish ladders to help not only the fish but also the entire ichthyofaunal population.”

Some experts also believe the asprete has lived on Earth for up to 65 million years, earning the fish a reputation as a “living fossil.” Image by Alex Găvan.

In 2020, scientists found 12 aspretes, which is the highest number of fish ever counted during a single survey. Then, in 2022, researchers found 58, breaking the previous record.

Marginean says conservation efforts likely helped the asprete begin to recover. However, he says he also believes there previously weren’t enough surveys done on the species to fully understand its abundance and distribution.

Based on the most recent survey that found 58 individuals, Marginean says he believes there are likely 300 to 350 individuals in the Vâlsan River.

“It’s really encouraging,” Marginean says. “They are trying to survive, holding on, but a lot of work is still needed to conserve it and to ensure its population for the generations to come.”

Elizabeth Claire Alberts is a staff writer for Mongabay. Follow her on Twitter @ECAlberts.

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