Last year, a fisherman caught the world’s largest freshwater fish, the Mekong giant rat, in the Mekong River in Cambodia. After tracking the fish for a year, researchers publish research on the mysterious species.

In June 2022, in a remote location in Cambodia, a fisherman reeled in a giant freshwater stingray. Fisher contacted researchers from the USAID-funded Miracle of the Mekong Project, a project that aims to protect the unique Mekong River, the fish that live in the river, and the fishing communities that rely on the river’s health and productivity.

Upon arriving at the site of the record catch, the Mekong Miracle team attached an acoustic tracking device to the fish. The project worked to implement tracking technology that allows researchers to study the movements of fish and where they stay, and the giant stingray was the first fish to be fitted with the device.

The University of Nevada, Reno’s Global Water Center is part of the international collaborative project Wonders of the Mekong. Global Water Center students and faculty have traveled to Cambodia many times to support research projects, collect data, and release fish.

The elusive giant freshwater rat is listed as endangered by the International Union for Conservation of Nature, but in Cambodia’s reaches of the Mekong River, fish populations appear to be relatively stable. However, this species faces threats from habitat fragmentation from the potential construction of hydropower dams, pollution and overfishing. The Cambodian government recently proposed establishing the Mekong River as a UNESCO World Heritage Site, which would boost conservation efforts.

Now, after collecting data for a year, the Mekong Wonder researchers are publishing their work in a special issue of the journal Water, an open access peer-reviewed journal. This issue, titled “Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation,” will feature three articles from the Mekong Miracle team.

“The information we learn about rat and other critically endangered fish is critical not only to our efforts to ensure the survival of the world’s largest freshwater fish, but also to the conservation of areas of great fisheries production that provide food for millions of people.” ” says Zeb Hogan, a professor of biology at the University of Nevada, Reno, who leads the Wonders of the Mekong research project that launched the study.

The first research paper shares data on the movements of nearly 300 fish in the Mekong River representing 27 species, including the giant freshwater wrasse, and how the construction of proposed hydroelectric dams on the Mekong River could affect the fish and the impacts of Cambodia’s designation of the Mekong River as a UNESCO World Heritage Site could have in this region.

The second article is an overview that brings together all the known information about the giant freshwater stingray. The research includes interviews with local fishermen who reported even bigger fish than the record fish caught last June. There is a possibility that there is another type of freshwater stingray, but more research needs to be done. The review highlights how understudied the fish is.

A third research article discusses how monitoring information can be useful in determining fish stocks for the conservation of the giant freshwater Mekong duck. Using acoustic tracking information, the researchers show that the giant freshwater stingray they tagged tended to stay in the same deep pool of water, meaning the establishment of fish reserves could be critical for the fish.

Research gathered on the giant freshwater rat will inform policy decisions made about the Mekong River, helping to protect the fish and people who rely on the Mekong.

By Editor

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