Habitat predilection of loach species Aborichthys uniobarensis through analysis of physicochemical parameters in Poma River, Arunachal Pradesh, Northeast India

The Poma River in Arunachal Pradesh serves as the primary habitat for Aborichthys uniobarensis, an ornamental fish species endemic to biodiversity hotspot. The  present study aimed to investigate the habitat characteristics of Aborichthys uniobarensis within the Poma River. Given the species' predominant presence in this river, understanding the water quality of the Poma River is crucial for further biological research, and of course conservation aspect of this fish species within in-situ as well ex-situ habitat. Over a two-year period (January 2018 to December 2019), the study assessed various physicochemical parameters (pH, water temperature (WT), dissolved oxygen (DO), biochemical oxygen demand (BOD), total dissolved solids (TDS), free carbon dioxide (FCO2), alkalinity, total hardness, electrical conductivity (EC), and salinity) at three sites along the Poma River with seasonal comparisons. Water samples were randomly collected in the morning between 6 a.m. to 10 a.m. Samples were analysed based on the standard methods of APHA (2012). The results indicated consistent conditions across sites but significant variations by season and year (Kruskal-Wallis and Mann-Whitney tests). Minimum values recorded were pH 6.29, WT 18.62°C, DO 6.55 mgL-1, BOD 3.85 mgL-1, TDS 29.78 mgL-1, FCO2 3.89 mgL-1, alkalinity 37.25 mgL-1, total hardness 23.71  mgL-1, EC 57.22 µs/cm, and salinity 0.05 ppt, while maximum values were pH 7.42, WT 25.43°C, DO 7.80 mgL-1, BOD 5.42 mgL-1, TDS 71.12 mgL-1, FCO2  6.48 mgL-1, alkalinity 59.34 mgL-1, total hardness 45.62 mgL-1, EC 117.33 µs/cm, and salinity 0.07 ppt. Simpson correlation tests revealed significant positive and negative correlations among the parameters. PCA analysis highlighted that WT, DO, pH, TDS, BOD, and FCO2 (both physical and chemical factors) have a greater influence on supporting A. uniobarensis, other fish species and the overall health of the river. As the values of habitat parameters were within the acceptable range, the River Poma is congenial for A. uniobarensis along with other species available in this particular riverine habitat.