New freshwater fish species discovered in Maharashtra’s Western Ghats, study finds

Newly discovered freshwater species Opsarius geminus. Pic/Beta Mahatvaraj

A new species of freshwater fish has been described from a tributary of the Krishna River in Maharashtra's Western Ghats, while a second species, originally discovered by British ichthyologist Francis Day in 1869 and forgotten for over a century, has been brought back to attention.

The research was led by Mumbai-based independent researcher Balaji Vijayakrishnan, along with Moulitharan Nallathambi, Praveenraj Jayasimhan and JD Marcus Knight, and published in Zootaxa, a leading scientific journal.

Koyna twin

The newly described species, Opsarius geminus, was collected by Balaji from the upper reaches of the Koyna River, a major Krishna River tributary in Satara district. Its name, geminus - Latin for "twin" - reflects its striking resemblance to Opsarius barna, a related species found in the Ganges-Brahmaputra river system.

The authors said fish previously identified as Opsarius barna in surveys of the Krishna River in Maharashtra are most likely misidentified specimens of the newly recognised species, highlighting how closely related fish can be confused in the field.

Lost species

The team also revalidated Barilius papillatus, first described in 1869 from the Cossye River in Odisha. Long misclassified as Opsarius barna, researchers used fresh samples from the Mahanadi River and historical specimens from Sydney's Australian Museum to confirm its distinct identity.

Conservation impact

Researcher Balaji Vijayakrishnan said, "The Opsarius genus now counts 36 global species, with seven in the Western Ghats." He added accurately identifying small, easily overlooked fish is crucial for freshwater conservation, as species cannot be protected or their true ranges understood until they are correctly named and distinguished from similar species.