Freshwater fish scientists had a busy year. A new report says taxonomists described 309 new species of freshwater fish in 2025, almost one new description for each day of the year.
The tally comes from SHOAL, the IUCN Freshwater Fish Specialist Group and the California Academy of Sciences. It is the highest annual total since 2017, and the third-highest since 1758, when scientists began keeping records.
The new species were recorded across five continents and from habitats including limestone caves, peat swamps, wetlands and rivers. Most are endemic, and some are already at risk of extinction.
Asia led the count with 165 newly described freshwater fish species. South America followed with 91, then Africa with 30, North America with 20, and Europe with three.
“If there’s one thing this report shows, it’s that our planet’s rivers and wetlands are still full of surprises,” Michael Edmondstone from SHOAL told Mongabay in an email. “We hope this report sparks curiosity about freshwater life.”
Among the new species are two cave-dwelling fish in China, Yang’s plateau loach, Triplophysa yangi, and the Sichuan mountain cave loach, Claea scet. Both are adapted to permanent darkness.
Museum specimens stored in Germany also led scientists to identify two new species from East Africa.
In the Democratic Republic of Congo, scientists described four new killifish species from the Nothobranchius group. These fish live in wetlands and complete their life cycle in rain puddles within a few weeks. They hatch, grow and reproduce before the water dries up.
Once the puddles disappear, drought-resistant embryos remain buried in mud until the next rains arrive and the cycle starts again. Their short lives in ephemeral pools leave them exposed to disruptions in rain patterns.
Of the 100 Nothobranchius species listed on the IUCN Red List, nearly three-quarters are already threatened with extinction.
One of the other newly described species is the sicklefin redhorse, Moxostoma ugidatli, from the Appalachian Mountains in the United States. At 60 centimetres, it is possibly the largest fish described in the last century from North America.
Its name comes from a Cherokee expression for “wearing a feather,” a reference to its feather-like, sickle-shaped dorsal fin.
The report says freshwater fish are one of the most threatened groups of vertebrates. Their habitats are disappearing because of pollution, overextraction of water, invasive species, changing weather patterns due to climate change, and overharvesting.
One of the newly described species from Kenya, Nothobranchius sylvaticus, is already critically endangered.
“There is a risk that many freshwater fish species will disappear without us knowing about them,” Richard van der Laan from CAS told Mongabay by email.
The report says a formal scientific description is needed before species can be assessed for extinction risk, regulated under wildlife trade agreements such as CITES, and included in management plans.
“Until species are formally identified and named, they remain largely invisible from a conservation perspective,” Edmondstone said. “Recognising them scientifically is the essential first step toward protecting them.”
The report also notes the rainbow killi, Nothobranchius iridescens, was identified in 2013 but only described in 2025 from the Democratic Republic of Congo because there was no road access to collect specimens until recently.
📸 credit: Cisamarc, Wikimedia Commons, CC BY-SA 4.0
