Guwahati: A dead fish specimen collected from a fisherman’s net in the Dikhu river of Nagaland turned out to be a new fish to science.

It was not as easy as it looks. The rivers were flooded and the scientists were looking for live specimens for months. 

J. Praveenraj, a scientist at the Division of Fisheries Science, ICAR-Central Island Agricultural Research Institute, Port Blair, who identified the new fish species- Pethia dikhuensis, said in 2021, Mr Limaakum, who is an assistant professor in the Department of Zoology, Fazl Ali College, Nagaland, shared photos of a dead colourful barb supposedly collected from a fisherman’s basket with me.

“I found it interesting and shared the same with Dr John Daniel Marcus Knight, who is an expert on Indian barbs. Dr Knight told me to try collecting live specimens. I passed the information to Mr Limaakum who took a lot of effort to collect it. Initially, the mission failed as the rivers were flooded and targeting the particular fish in that large river was not an easy task,” J. Praveenraj told EastMojo

He said during the year 2022, Limaakum was successful in collecting live specimens of both male and female fishes and the first live photos of it were captured and shared with me by Nungsangtemjen Imchen, who works in the department of agriculture. 

Pethia are generally easy to identify if one gets to know about the live colouration of both sexes.

“A DNA and comparative study of the bones, colour and body characters, revealed the species to be new to science. As per my collaborator Mr. Limaakum’s wish, we named the species ‘Pethia dikhuensis’ after the river Dikhu, Nagaland from where it was collected,” he said.

Live specimens of the new species were collected by cast net, photographed alive using a small glass tank and subjected to morphology, DNA and bone studies. 

The work has been published in Zootaxa, a reputed international journal for taxonomic studies.

Pethia dikhuensis is currently known only from the Dikhu River, a tributary of the Brahmaputra, in the Mokochung district of Nagaland.

Pethia dikhuensis is unique among all species of barbs because the male fish of this species have reddish-orange fins and bodies. The new fish is consumed by locals but also possesses a good ornamental value due to the attractive colour.

The genus Pethia are small sized-fishes (5-8 cm) commonly called ‘barbs’. These fishes are endemic to the Indian subcontinent and Myanmar.

Pic credit- Nungsangtemjen Imchen

A total of 38 valid species of Pethia genus are known to occur in India and its bordering countries, of which 18 species occur in the northeastern states and Bangladesh.

Nagaland is drained by 11 major rivers, which are tributaries of the larger Brahmaputra River system. The rivers of Nagaland are relatively less explored compared to other Northern Eastern states of India. The fish fauna of this region is poorly studied and our team is taking efforts to explore, discover and describe new species from this region.

“Last year a small miniature catfish called Pseudolaguvia vespa was also discovered by our team. The discovery of P.dikhuensis suggests that the streams and rivers of this region may harbour many more undescribed species of fish, and therefore deserves increased survey efforts,” he said.

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