Chhimi Dema 

Bhutan should consider designating the Aiechhu Proper (Maochhu) as Bhutan’s free-flowing river basin, according to baseline research from the National Research and Development Centre for Riverine and Lake Fisheries.

The study titled, “Diversity of fishes across hydrological basins and elevational gradients in eastern Bhutan: A preliminary analysis”, stated that Aiechhu serves as an ideal choice for a free-flowing river as it is subjected to relatively few anthropogenic impacts.

Moreover, Aiechhu’s water source originates from within Bhutan, and the basin which has minimal potential for hydropower development compared to other river basins makes it a potential choice to keep it as a free-flowing river, the study stated.

Internationally, the designation of at least one river as a free-flowing river is gaining attention among environmental agencies and conservationists to address the potential impact on aquatic diversity.

However, the study called for an extensive review of existing information and further studies to strengthen the current knowledge of the ichthyofauna (fish of the region) diversity in Bhutan to adopt appropriate conservation plans.

The study was published in the Bhutan Journal of Animal Sciences in July this year.

The research samples were collected from three hydrological basins Aiechhu, Manas, and Nyera-Amachhu.

The Manas basin include four sub-basins Mangdechhu, Chamkharchhu, Kurichhu, and Drangmechhu.

The research found a total of 108 species of fish in the 496 sampling sites covering the four river basins.

Cypriniformes (an order of ray-finned fish) represented the highest number of species followed by Siluriformes (Catfish), Perciformes (Perch-like fishes), and Sunabranchiformes (Swamp eels).

“Of the 108 species enumerated from rivers across Eastern Bhutan, the highest number of species were detected in the Aiechhu river basin followed by Manas and Nyera-Amachhu,” the research stated.

The comparison among the three river basins indicated the Aiechhu river basin contains the highest taxonomic diversity of fish in terms of orders, families, genera and species.

Aiechhu Proper (Maochhu) also showed a higher species richness than Manas and Nyera-Ama river basins.

The study serves as a preliminary baseline for the ichthyofauna in eastern Bhutan and was aimed to strengthen conservation efforts of aquatic biodiversity.

The study was initiated with support from the Bhutan Trust Fund for Environmental Conservation. It is authored by researchers Changlu, Sangay Norbu, Karma Wangchuk, Gopal Prasad Khanal, Singye Tshering, and Pema Tshering from the riverine and lake fisheries research centre in Haa.