Integrating land-use dynamics, water quality, and multi-criteria ecological suitability for fish sanctuary prioritization in three major river basins of Bangladesh

Riverine ecosystems in monsoon-dominated regions are increasingly constrained by interacting pressures from land-use change, hydrological alteration, and water-quality degradation, yet these drivers are rarely assessed within a unified framework. This study presents a reproducible, basin-scale framework integrating multi-season (monsoon–dry) land-use dynamics (2000–2020), hydrochemical assessment (including nutrients and trace metals), and GIS-based Multi-Criteria ecological modeling to delineate fish sanctuary suitability across the Ganges–Padma, Brahmaputra–Jamuna, and Barak–Meghna basins of Bangladesh. Results showed a 1.5% decline in monsoon water extent, 12.7% decline in the mapped monsoon vegetation class, and a 25% increase in dry-season vegetation, indicating reduced floodplain connectivity and progressive habitat simplification. Water quality further constrained habitat suitability, with 37.5% of site–season observations classified as poor, very poor, or unsuitable, frequent dissolved oxygen concentrations below 5 mg L − 1 , and localized heavy metal concentrations exceeding guideline thresholds. The integrated Suitability Index identified only 4.9% of the landscape as highly suitable, characterized by perennial water depth, strong connectivity, and low pollution levels. Overall, the findings demonstrate that habitat degradation in large river basins is driven by the combined effects of landscape and hydrological change and hydrochemical stress. The proposed framework provides a transferable decision-support tool for prioritizing conservation interventions in data-scarce, climate-sensitive river systems.