POST-MONSOON COMPOSITION OF ICHTHYOFAUNA ALONG THE PUNATSHANGCHHU AND ITS TRIBUTARIES AT THE HYDROPOWER PROJECTS AREA

Abstract

Hydropower promotors in Bhutan are mandated to address impacts on aquatic biodiversity through proper conservation and management plans formulated through regular monitoring of impacted areas. This assessment presents findings from post-monsoon monitoring of mainstem Punatshangchhu and its tributaries within the Punatshangchhu Hydropower Project area (PHPP – I & II) from November 22^nd – 26^th, 2021. Though Kruskal-Wallis test and multiple pairwise comparison the study recorded significant differences (p<.05) in physiochemical properties such as pH, dissolved oxygen (DO) and total dissolved solids (TDS) within the mainstem Punatshangchhu and its tributaries, all accessed variables were found within the permissible limits for fisheries and surface water. The differences in catch per unit effort (CPUE) among the downstream, impacted (future dewatered) and upstream zones of Punatshangchhu were not statistically significant. Lower CPUE, abundance and size observed during present monitoring compared to the post-monsoon monitoring conducted in 2018 and 2019 indicated possible changes in population structure of Schizothorax richardsonii, the dominant fish along the Punatshangchhu. However, nonstandard sampling adopted over years makes comparison among years unreliable requiring adoption of consistent assessment approaches during the subsequent monitoring for comprehensive realization of conservation goals.