Mapping Fish Habitat Stress in a Large Floodplain Lake: A Hydrodynamic Modelling Approach for Seasonal Water Temperature Dynamics

ABSTRACT Lake water temperature serves as a significant indicator of global climate change, and its seasonal variability will affect fish habitats, their growth and reproduction cycles. Investigating potential fish habitats and periods of habitat stress is crucial for fisheries and the conservation of rare species, offering both economic and ecological benefits. This study employed a hydrodynamic model coupled with heat flux exchange to simulate the seasonal variations of water temperature in Poyang Lake, China's largest freshwater lake. Using optimal water temperature ranges of dominant fish species in this large lake, we identified periods of fish habitat stress and mapped the spatial distribution in the number of optimal days. Our results reveal distinct spatial patterns in the seasonal distribution of water temperatures in Poyang Lake, such as significant temperature differences in spring and winter compared to smaller differences in summer and autumn, accompanied by a temperature gradient from southeast to northwest. Additionally, our simulations suggest that fish are more prone to habitat stress from December to March, with thermal stress occurring more frequently during this period. This research establishes a correlation between fish habitats and water temperatures in China's largest lake, which could provide essential information for fisheries management and the conservation of ecologically and economically important fish species.