Fairy Dandiya swims back from oblivion

A rare endemic fish species that has remained a mystery for 53 years will make it to Sri Lanka’s freshwater checklist after it was rediscovered in the streams of Athwelthota - by Malaka Rodrigo

The Wildlife Conservation Society of Galle (WCSG) research team had been busy surveying the fish in streams of Athwelthota in the first week of July hoping to find Martinstine’s Goby. The fish had been scientifically described based only on a single specimen collected from these pristine streams.

 

Luck though seemed not with them, until a researcher noticed a fish with different characteristics in their net. They quickly slipped it into a sliding tank for further observation. It looked similar to the Vateria Flower Rasbora (Hal Mal Dandiya) which is rather common in these streams, but its body depth was less than that of the Hal Mal Dandiya. It was about two cm long with the male having a distinctive iridescent copper-red upper part of the eye.

“We immediately realized this was a special fish,” said Madura de Silva, WCSG president. The research team’s first impression was that they had discovered a new fish. They shared the photos with fish experts of the country and the answer was soon found. Rohan Pethiyagoda – Lanka’s foremost expert on fish identified it as Meinken’s Fairy Rasbora (Rasboroides nigromarginata) that had been scientifically described in 1957.

German scientist H.Meinken had made this discovery based on some specimens he received through the ornamental fish trade. But although Meinken knew it was exported from Sri Lanka, he had no idea where exactly the original population was; hence the species had remained a mystery for 53 years.

This endemic fish was thus not included in the country’s recent Freshwater fish checklists. Now it it will be -making the tally 85 fish species. Sri Lanka has 44 endemic freshwater fish though this number is also under review. The new fish’s scientific Latin name Rasboroides nigromarginata reflects its other distinctive character of having a black margin on its fin. The Fairy Rasboras are endemic to south-western Sri Lanka where they inhabit streams associated with rainforest habitats.

Athwelthota has been a widely researched area for freshwater fish, but Meinken’s Fairy Rasbora escaped previous researchers’ watchful eyes. Pethiyagoda who had done a comprehensive freshwater fish study in late 1980 said, “Although I had collected fish at this very same location when writing my book, I missed this one,” adding “it is a remarkable discovery.”

The Wildlife Conservation Society of Galle is expected to include the Rasboraides nigromarginata on the list of strictly protected fishes considering its rarity. “We think Meinken’s Fairy Rasbora is restricted only to these streams in Athwelthota,” said Madura, highlighting the need to protect these freshwater sources conserving their habitats.

He fears the fish could also be a victim of over collection as Athwelthota streams are frequently raided by ornamental fish collectors who catch fish for export.

National Survey on Freshwater fish
The rediscovery of Meinken’s Fairy Rasbora is the fruit of the National Survey on Freshwater Fishes conducted by WCSG together with the Biodiversity Secretariat of the Ministry of Environment. The research team had already discovered several species of freshwater fishes that are new to science as part of this survey started last year.

Systematic Freshwater Fish study in Sri Lanka began as far back as 1830 by Pieter Bleekers. During this period of 170 years, nine major research studies were carried out disclosing the rich diversity of Sri Lanka’s freshwater fish. The last major research was done in late 1980 by Rohan Pethiyagoda bringing to light many more fresh water fishes. Assessment of the population status of each freshwater fish species in major river basins and assessment of the species that have not been recorded for a long time - more than 30 years are the main objectives of the present survey. Studying the river basins in the north and east is also one of the major objectives of the project.

The research team who made the discovery included Nadeeka Hapuarachchi, Sameera Akmeemana, Krishan Wewellwala, Indika Wijesekera and Lasith Siriwardena. They were thankful to the Nations Trust Bank whose funds helped support this research.

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