Diversity of fishes across hydrological basins and elevational gradients in Eastern Bhutan: A preliminary analysis

Abstract

Bhutan’s water resources span a tremendous elevational gradient and are home to a diverse ichthyofauna. However, much of the aquatic biodiversity remains understudied and little is known about the ecology of native species. In an effort to strengthen Bhutan’s existing fishery database, the National Research and Development Centre for Riverine and Lake Fisheries, Haa, conducted an ichthyofauna assessment from 2017-2019 at 496 sampling stations spread across three hydrological basins in eastern Bhutan: Aiechhu, Manas and Nyera-Amachhu. A total of 108 fish species, representing 47 genera, 19 families and 7 orders, were recorded during the study. The highest number of species and endemic fish were concentrated along the Aiechhu hydrological basin, particularly the Aiechhu proper (Maochhu) and below <500 meters elevation. Based on these findings, the Aiechhu proper (Maochhu) appears to be best choice for retaining a free-flowing river in Bhutan and planned future hydropower developments <500 meters above sea level should be reconsidered.