A study of Paracanthocobitis botia, hill stream zipper loach with ecological and morphometric insights from an eastern Himalayan Tissa River system

Abstract

Different sections of Tissa river were surveyed to document it’s fish fauna from 2023 to 2024 in two seasons i.e. pre-monsoon and post-monsoon in the months of February to April and September to October respectively in both years. A total of 116 individuals of species Paracanthocobitis botia (Hamilton 1822), was recorded during the survey. Morphometric characters were studied based on 43 numbers of females and 37 number of male specimens. Sexual dimorphism in the species was marked by the presence of a horizontally oriented suborbital flap in males, typically extending from below the eye to the mid-region, which was absent in females. Spatial variation of species abundance were studied along with the physical habitat parameters like dissolved oxygen (DO), temperature, total dissolved solids (TDS), electrical conductivity (EC), salinity, altitude, flow and depth. Pre-monsoon season exhibited higher frequency of occurrence with total documentation of 52 individuals during pre-monsoon 2023 and 64 individuals during pre-monsoon 2024 season. While 15 and 35 individuals were recorded during post monsoon season in the year 2023 and 2024 respectively. P. botia in Tissa River displayed a mild preference for DO levels of 9-12 ppm, an altitude of approximately 500 m, and a water depth of 60 cm. No significant variation in abundance was observed in relation to changes in EC, flow rate, pH, Salinity, TDS or temperature, suggesting that the species may function as a generalist and capable of persisting across a broad spectrum of environmental conditions.