A molecular survey based on eDNA to assess the presence of a clown featherback (Chitala ornata) in a confined environment

BACKGROUND: The importance of the inland fisheries sector in food security as a provider of much-needed protein and income supplier has been highlighted. This is especially the case in poor rural communities in developing countries. Inland capture fisheries in Thailand are in place nationwide in rivers, lakes, swamps and reservoirs. The clown featherback (Chitala ornata) is popularly consumed and is an economically important fish in Thailand which is often used in food products such as fish balls and fish cakes. Along with other fish species, the clown featherback is one of fish of inland fisheries at Phayao Lake. Recent fish surveys from 2016-2018 at Phayao Lake using netting and electrofishing found that the number of clown featherback have been reducing since 2016 and could not be detected at all by 2018. This is despite the fact that there are still reports of their presence in the lake from locals. METHODS: We developed an eDNA-based method for detection of the clown featherback in Phayao Lake as an alternative tool. Water samples were collected in three different sampling months (February, June and September) at six sites located in the lake. Species-specific primers and the probe were designed to amplify a 183 bp fragment of the cytB region of the clown featherback. RESULTS: eDNA of the clown featherback can be detected in all different sampling months and sites. Concentration of the clown featherback found in Prayao Lake showed no difference over sampling month but between collecting sites. This proves that eDNA based survey is a sensitive and useful tool for monitoring and surveying the clown featherback at any time of the year.