Elevated CO2 and CH4 emission rates in feeding areas of small aquaculture fish ponds.

Aquaculture ponds are increasingly recognized as an important source of greenhouse gas emissions to the atmosphere; however, the influence of feeding practices in earthen aquaculture ponds remains poorly understood. This study aimed to quantify how feeding practices and feeder types shape the spatial heterogeneity of carbon dioxide (CO2) and methane (CH4) emissions in small, shallow earthen aquaculture ponds. We investigated dissolved CO2 and CH4 concentrations and air-water fluxes across littoral, feeding, and pelagic areas in seven small (<3 ha), shallow (mean depth <1 m) aquaculture fish ponds in central China during both farming and non-farming periods, with ponds operated using fixed-point and broadcast feeders. Water samples were analyzed for key physicochemical variables, including temperature, pH, total ammonia nitrogen, and dissolved organic carbon. Potential drivers were evaluated using extreme gradient boosting together with Spearman correlation analysis. The results showed that feeding areas had markedly higher CO2 and CH4 fluxes (2.2-2.9 times those of other areas), primarily due to localized accumulation of feed-induced organic matter under constrained hydrodynamic mixing. Total ammonia nitrogen emerged as the primary positive predictor for CO2 emissions, while C/P ratio acted as a negative predictor for CH4 emissions. Broadcast feeders substantially expanded the spatial extent of high-emission areas, leading to a 20% underestimation of total carbon emissions when spatial variability was not accounted for. These findings highlight that feeding-related hotspots and mixing conditions can strongly bias pond-scale emission estimates, underscoring the need for spatially explicit monitoring and improved feeding and water circulation management to support low-carbon aquaculture.