Ecological assessment of Oxbow Lakes: Interplay of water quality, plankton communities, and commercial fish populations in south-western Bangladesh

Abstract

Oxbow lakes (baors) are semi-closed freshwater ecosystems that contribute substantially to inland fisheries and livelihoods in southwestern Bangladesh, yet their ecological productivity remains insufficiently explored. This study aimed to assess the physicochemical conditions, plankton diversity and abundance, and fish community structure of three baors—Bukbhora, Jhapa, and Khedapara—from July 2023 to June 2024. Monthly water quality monitoring, plankton sampling, identification, and fish community surveys were conducted to evaluate seasonal ecological patterns and production potential. Water temperature ranged from 21–33 °C, pH from 7.5–8.1, dissolved oxygen from 5.5–6.5 mg L⁻¹, alkalinity from 165–169 mg L⁻¹, and hardness from 169–179 mg L⁻¹, indicating generally favorable conditions for aquatic productivity and fish growth. Nitrite-nitrogen remained below the detection limit (