Effects of climate variability on freshwater fisheries in Cambodia's rice field fisheries: a longitudinal cohort study

Background: Projections suggest that by 2050, climate change will reduce global fish catch by 3–13%, with fish catch falling by as much as 30% in some tropical marine systems. Freshwater fisheries are particularly susceptible to the warming effects of climate change because shallower, hydrologically distinct water bodies are easily affected by atmospheric temperatures and less easily accommodate fish migrations. Damage to freshwater fisheries is a problem particularly for poor and undernourished human populations, which are especially dependent on them. Despite the severity of projected climate change effects on fish catch and the risk to human health, few empirical studies have examined how fish catch is already responding to climate variability, the ways fishers are adapting to these changes, and how it affects people's consumption of fish, which are rich in micronutrients and fatty acids. We aim here to account for behavioural responses among fishers to identify the ecological effect of flood and weather on fish catch in Cambodian rice field fisheries, and patterns of fish consumption and nutrition in the local communities. Methods: In this longitudinal cohort study, we use a panel dataset collected by WorldFish of 400 households dependent on rice field fisheries over 3 years (19 distinct timepoints) to examine how changing flood patterns and temperature alter households' fish catch and whether fishing families respond by either adapting the effort put into fishing (ie, hours, time of day, or number of family members involved) or fish consumption. We analyse the net effect of biophysical changes on household fish catch, the effect of biophysical changes (flood, temperature, and rainfall) on household fish catch and fish consumption with the addition of controls for fishing effort, a key way that fishers might adapt to ecological changes, and the direct effect of biophysical changes on fishing effort and fish consumption. Findings: Preliminary results suggest that from November, 2012, to November, 2015, fishing families changed their fishing effort and practices to adapt to the effects of flood and temperature changes on fish catch. Updated data and analyses will allow us to disentangle these effects by using an identification strategy to separate the ecological effects of flood and temperature changes on fish catch from the ways households respond to changes in fish availability. Interpretation: Our results have broad implications for understanding the ways that climate change might affect the 10% of the global population that rely on small-scale fisheries in low-income countries. Analyses of fish catch will show the effects of flood and temperature changes on fish catch and how households respond to these changes. Further, analyses of the effects on consumption of fish will show how temperature potentially alters access to micronutrient-rich food. Our findings suggest the ways that the changing global climate might affect the health and wellbeing of natural resource-dependent communities. Funding: Financial support for this project was provided by the US Agency for International Development (USAID) through the Rice Field Fisheries Enhancement project and Cornell University's David R Atkinson Center for a Sustainable Future Postdoctoral Fellows Program. The contents and opinions expressed herein are those of the authors and do not necessarily reflect the views of USAID or the US Government