Scientists Stunned As Rare Killifish Thought Extinct Is Found Alive in Bolivia

A long-lost Bolivian killifish has been found alive, revealing a globally important hotspot for seasonal killifish diversity at risk from deforestation.

Researchers have confirmed the rediscovery of Moema claudiae, a seasonal killifish from Bolivia that had been considered possibly extinct. Finding this species again brings renewed optimism for its protection and for the conservation of the region’s wetland ecosystems.

Moema claudiae had not been observed for more than 20 years at its original site, which has since been destroyed and converted into farmland. Despite extensive surveys over the past two decades, no additional individuals were found, leading to its classification as Critically Endangered under IUCN criteria and its assumption of being possibly extinct.

Discovery in a remnant forest pond

During a recent field expedition, researchers Heinz Arno Drawert and Thomas Otto Litz located a surviving group of the fish in a small temporary pond preserved within a fragment of forest surrounded by agricultural land.

The rediscovery, published in the open-access journal Nature Conservation, marks the first confirmed sighting of the species in over twenty years. It allowed scientists to capture the first live photographs, document its behavior, and investigate aspects of its natural history that had never been recorded before.

Thomas Litz, one of the co-authors, said: “For me, it is something special to have rediscovered Moema claudiae. This has shown that we now have the opportunity to preserve this species in the wild. I am all the more pleased because Prof. Wilson Costa named this species after his wife Claudia, and I would like to take this opportunity to thank him especially for decades of collaboration and support.”

The site where the fish was found contained not only Moema claudiae but also six additional species of seasonal killifish. This makes it the most genetically diverse group of these fish recorded anywhere in the world.

The area’s distinctive environment, located at the transition between the Amazon forest and the Llanos de Moxos savannas, seems to foster this remarkable variety. However, fast-moving deforestation and the spread of agriculture are putting these habitats under severe pressure.

Ecological pressures and habitat loss

Following this discovery, scientists emphasize the urgent need to protect the area, as it is now the only known site harboring a wild population of Moema claudiae, as well as an exceptional global hotspot for seasonal killifish diversity.

Over the last 25 years, nearly 10 million hectares of forest were lost in Bolivia, including vital wetland habitats. Deforestation has accelerated dramatically in recent years, raising serious concerns for the future of many unique species and ecosystems.

“Without rapid and effective action to curb the irrational expansion of the agricultural frontier in Bolivia’s lowlands, we risk losing some of the world’s most important terrestrial and aquatic ecosystems, and with them the irreplaceable goods and services they provide,” added co-author Heinz Drawert. “We cannot hope to achieve true social and economic wellbeing unless we also maintain the functionality of the ecosystems that sustain it.”

Reference: “Rediscovery of a thought to be extinct beauty: a second chance for conservation” by Heinz Arno Drawert and Thomas Otto Litz, 14 November 2025, Nature Conservation.
DOI: 10.3897/natureconservation.60.160386

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