These results provide evidence that, despite recent poverty reduction in Bangladesh, children born in the southwest coastal region during peak salinity months have suffered from higher morbidity and mortality rates. For children born in peak salinity months, death probabilities in the 2018 and 2022 surveys are 25.2% and 13.3% higher, respectively. The evidence for diarrhea is mixed, with a probability 69.9% higher in 2018 but 16.5% lower in 2022. For stunting, children born in the peak salinity months have probabilities 8.8% higher in 2018 and 26.5% higher in 2022.

# **6 Summary and Conclusions**

the southwest coastal region of Bangladesh. At the same time, annual flux dynamics propel salinity changes so large that they can provide insights into future changes as high-salinity water moves steadily inland. This paper combines measures from river salinity monitors with fish sales records from neighboring wholesale markets to assess the magnitude, spatial distribution and fishing impact of salinity changes over the annual cycle in 2023. In traditional analyses, measured changes in river salinity are combined with species-level saline tolerance parameters to project changes in the spatial distribution of fish stocks. In this analysis, we incorporate two additional factors: differential responses to salinity change by fish species with similar survival limits for salinity exposure; and fishers’ search for more profitable fishing grounds as the fish respond to changing salinity. Together, these two factors determine fluctuations in fish catches as salinity changes.

Our econometric analysis shows that the complex interplay of species-specific relocation behavior and fishers’ search can generate very different catch patterns for fish that have similar or identical salinity tolerance ranges. For some species increasing salinity induces a sharp decline in the catch, while for others the interplay of relocation and fishers’ profit-motivated search can induce an increase in the catch. The strength of our results suggests that technically determined saline tolerance parameters have limited utility as predictors of the magnitude and spatial distribution of fish catch quantities as salinity changes. Since fish catch records of the type we have surveyed are commonly available, we believe that future analyses could profit from the evidence they provide.

To assess the implications for households at different income levels, we have performed separate econometric analysis for low-, medium, and high-price fish. We find great responsiveness to salinity change in all groups, but the response of the fish catch to salinity change is greatest in the high-price group. In a parallel exercise, we have performed an econometric analysis of the fish price response as varying salinity changes the typical catch size. We find a statistically significant but relatively modest price response for high-price fish, perhaps reflecting a greater quantity response for luxury commodities. However, for low- and medium-price fish we find no significant price response to salinity change. This somewhat surprising result may warrant further research, since it suggests that fish sellers in southwest coastal Bangladesh choose to keep prices relatively stable for fish that are marketed to households of more modest means. By implication, reduced stocks in high-salinity periods are rationed by non-price methods.

protein consumption in low-income households, with associated impacts on maternal/child nutrition and health. The magnitude of the impact will depend on whether poor consumers’ resources enable them to substitute other protein sources. Poverty has fallen significantly in Bangladesh during the past two decades, although the southwest coastal region has remained relatively poor by national standards. To test whether recent income growth has increased household resilience in this context, we analyze over 16