Assessment of the seasonal and altitudinal gradients in fish diversity of a tropical river of western ghats biosphere using multivariate analysis

Abstract

Abstract The study attempted to investigate the seasonal and spatial (altitudinal) gradients in fish diversity with respect to hydrobiological variables of Chaliyar river (encompassed in western Ghats biosphere). Fish and water quality samples were collected seasonally and analysed inorder to identify the drivers determining fish diversity of the river. 66 fish sp. belonging to 57 families and 12 orders were recorded during the study period (2017–2020). The year-wise diversity analysis revealed that higher diversity was recorded in 2019(1.43) compared to 2018. Seasonal and altitudinal (stretch wise) diversity analysis showed that the pre-monsoon season of 2017 (3.19) and lower stretch (2.18) of the river recorded the highest diversity. Phosphate (0.036ppm ± 0.039), calcium hardness (35.18 ± 101.61ppm), transparency (1.04 ± 0.6m), total hardness (330.21 ± 795.66ppm), and magnesium hardness (60.57ppm ± 142.42) were positive drivers influencing the diversity of Chaliyar as assessed using step-wise regression. Majority of fishes belong to least concern category except Horabagrus brachysoma (yellow spotted catfish) and Bhavania australis (westernghat loach). Community mobilisation, enhanced scientific interpretation and identification of appropriate habitat indices would be considered the next step in devising management measures in Chaliyar river.