The river ecosystems in Bhutan are robust and flourishing, according to findings from the ongoing fish fauna assessment that is underway in the eastern and central parts of the country.
This is mainly based on the presence of aquatic invertebrates (insects and river plants) found in the rivers of the country.
Officials from the National Research Centre for Riverine & Lake Fisheries (NRCR&LF) in Haa captured fish samples from Bamridrang, a tributary that joins the Drangmechu river system in Trashigang recently.
The team captured two species of freshwater catfish – parachiloglanis and pseudecheneis species – from the stream.
The fish fauna assessment that began in 2013 is being conducted to find fish diversity including composition and diversity of fishes in different water systems in the country.
A similar study was conducted for the western water system between 2013 and 2016. The team discovered 104 species of fishes from the Amochu, Wangchu and Punatshangchu basins.
Assistant laboratory officer with NRCR&LF, Pema Norbu, said that the study is being carried out to formulate a database on fishes in Bhutan. “Once the second phase of the survey is completed, a detailed database and a book on fishes of Bhutan would be published by the centre.”
Another assistant laboratory officer, Sonam Dorji, said they know there are fishes in a particular river but are not able to identify what kind of fish is actually found there. “There is no proper data available on fishes so far.”
He said that once completed, the database should help people identify what species of fishes are found in different river systems.
Apart from forming a database, Sonam Dorji said that the survey would help in planning and coordinating any developmental activities without affecting the aquatic biodiversity.
It was learned that construction of dams and bridges including approach roads over a river system had a direct correlation to the presence of fishes in that water system.
The second phase of the survey began from Bumthang and would cover the reaming six eastern dzongkhags.
The team collects samples of fishes mostly from the tributaries and takes it for DNT testing. “We are not able to access the main river given the size of the water. We are focusing on the tributaries since it joins the main river and the same fishes found in the river are expected to be found in the tributaries,” said Pema Norbu.
In Trashigang, the team also collected samples from three tributaries in Rangjung that join the Gamrichu river system.
Reinforced with some high-tech fishing gears in phase-II, Sonam Dorji said that it has become much easier to catch the fishes compared to the first phase of the survey. The team uses electro-fishers to lure the fishes into the nets by making them paralyzed without killing them.
With the help of the new gear, the team managed to capture the mottled eel, a rare fish known for remaining secluded in deep waters.
However, officials said that limited time and manpower were some of the challenges faced in conducting the survey. “To study the whole water system in the country and the presence of fishes in it would require more time,” said Sonam Dorji.
Accessibility to the big rivers and difficult terrain were also some of the other challenges.
Bhutan Trust Fund for Environmental Conservation funded the project with Nu 12.59 million and it would be completed by June next year.
Younten Tshedup | Trashigang