The Wonders of the Mekong project team is investigating the cause of the large number of endangered Tenualosa thibaudeaui freshwater fish, sometimes referred to as the Laotian shad, being caught by fisherman in Ratanakkiri province since December 2021.

The Tenualosa thibaudeaui is listed as “vulnerable” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

Since 2017, fishermen in the northeastern province reported that this rare species of herring was almost never caught, according to a new report released by the Wonders of the Mekong project on March 21.

But since December, fishermen in Ratanakkiri have been catching tens of kilogrammes of the rare species a day.

“This species is starting to multiply again,” it said.

According to the report, a group of postgraduate students working on the project recently collaborated with officials from the Freshwater Fisheries Research Institute to study the situation of this fish throughout the Sekong, Sesan and Srepok basins, as well as inspecting fish markets and interviewing local fishermen.

Their mission highlights the importance the scientific community places on the reporting of local people, and their observations of the local ecosystem and its organisms.

The knowledge of local people helps officials to understand more about the great Mekong River system and its maintenance for the future.

“This season, the shad are moving like never before along the Sre Pok River, a tributary of the Mekong River. The reason they are so plentiful is still a mystery,” the research team said.

Researchers are still working on the status and reproduction of this species to find out the truth.

Fisheries Administration spokesman Ung Try told The Post that the proliferation of rare fish in the past three months has made some local fishermen happy, but scientists are not yet certain about the reason for this strange change.

“We will be happy if the results of our research show that the Laotian shad are indeed abundant, but we are still in the process of carrying out studies,” he said.

“Sometimes at the beginning of the year a species is abundant, but by the end of the year it is scarce again,” he added.

According to Try, scientific research on rare species of fish, plants and animals cannot be carried out in just one or two days. It requires three to five years of carefully collected data before any analysis can be considered definitive.