Abstract
Abstract
Bangladesh has rich inland and coastal fish diversity that is vital for biodiversity conservation, food security, and the livelihoods of millions of people. However, this diversity is increasingly threatened by climate variability through rising temperature, erratic rainfall, floods, droughts, cyclones, sea-level rise, and salinity intrusion. This review synthesizes existing evidence on how climate variability affects fish diversity across rivers, floodplains, wetlands, estuaries, and coastal ecosystems of Bangladesh. Following PRISMA 2020 guidelines, relevant literature was collected from major academic databases and institutional reports, screened using defined inclusion and exclusion criteria, and synthesized through a narrative thematic approach. The review found that climate variability affects fish assemblages through multiple interacting pathways, including thermal stress, altered hydrology, habitat fragmentation, deterioration of water quality, disruption of spawning and migration cues, and changes in food-web structure. Inland water bodies, particularly rivers, haors, beels, and floodplains, show declining species richness and increasing dominance of tolerant and opportunistic species under irregular flooding, drought, and warming. In coastal and estuarine ecosystems, salinity intrusion, reduced freshwater inflow, and extreme climatic events are reshaping fish community structure and degrading critical nursery habitats, Migratory species such as hilsa have been identified as particularly vulnerable, and this is well documented in literature due to relatively extensive research attention. However, several other migratory fish species have received far less scientific focus, resulting in significant knowledge gaps regarding their population status and climate-related responses, even though they are likely experiencing similar pressures. The review also highlights those anthropogenic pressures, including overfishing, pollution, habitat conversion, and hydrological alteration, amplifying climate-related biodiversity loss. Overall, sustaining fish diversity in Bangladesh will require integrated climate-resilient fisheries management, habitat restoration, ecosystem-based conservation, and long-term research and monitoring.