Abstract ID: 3.11034 | Accepted as Talk | Talk/Oral | TBA | TBA

Research on river systems in the eastern Himalaya are extensively skewed towards taxonomical aspects while their ecological information particularly in the state of Arunachal Pradesh remains scare. In order to address this persisting knowledge gap, the present study aims to document fish assemblage patterns as well as their associations with the local habitat parameters in the Tissa river basin flowing along the easternmost borders of Arunachal Pradesh near the India-Myanmar border, serving as a significant aquatic ecosystem in the region. The study was carried out in two seasons, pre-monsoon (Feb-March) and post-monsoon (Sep-Oct) from 2023 to 2024. A total of 48 fish species belonging to 14 Families across four orders were recorded. Fish Species richness varied from 2 to 20 along entire tissa river system where chettum river, a small tributary of river Tissa recorded highest diversity (H’= 2.48). The Principle Component Analysis was employed to distinguish the different stream orders on the basis of habitat parameters like pH, temperature, TDS, Conductivity, DO, Salinity, mesohabitat counts, flow, depth profile, substrate type, percentage of fish cover and altitude resulting in three distinct orders (higher, middle and lower). Fish abundance (site wise) data and habitat parameter data was then subjected to Canonical Correspondence Analysis to test the association of habitat parameters on fish abundance. The CCA results revealed that the abundance of fish species Schizothorax richardsonii and Exostoma labiatum were strongly associated with high altitude, lower pH and water temperature. Large carbs like Neolissochilus hexagonolepis, Bangana devdevi and Tor putitora were associated with higher ordered streams. Other species like Channa stewartii, Danio assamilia, botia rostrata, Garra annandalai showed strong association with warmer water and higher conductivity streams. All univariate and multivariate statistical analyses were performed using R-software (version 4.4.1 2024-06-14). Additionally anthropogenic threats like overfishing, utilization of destructive fishing technique (batteries and converters) , habitat degradation & fragmentation, wastewater runoff and river bed mining were identified as significantly impact the aquatic ecosystem.