Fisheries constitute an important source of livelihoods for tens of thousands of poor people in the southwest coastal region of Bangladesh living near the UNESCO Heritage Sundarbans mangrove forest, and they supply a significant portion of protein for millions. Among the various threats fisheries in the southwest coastal region and Sundarbans mangrove forest will face because of climate change, adverse impacts from increased aquatic salinity caused by sea level rise have been identified as one of the greatest challenges. This paper focuses on 83 fish species consumed by poor households in the region. Using the salinity tolerance range for each species, 27 alternative scenarios of climate change in 2050 were investigated to assess the possible impacts of climate change and sea level rise on aquatic salinity, fish species habitats, and the poor communities that consume the affected fish species. The results provide striking evidence that projected aquatic salinization may have an especially negative impact on poor households in the region. The estimates indicate that areas with poor populations that lose species are about six times more prevalent than areas gaining species.