The reproduction of Chinese sturgeon,Acipenser sinensis exhibits high sensitivity to ambient water temperature. Spawning initiation demonstrates strong coupling with water temperature decreases to approximately 18.5°C, indicating a species-specific temperature preference. Changes in the Yangtze River's thermal regime in 1998 and 2006 disrupted the synchronization between gonadal development and spawning triggers. These alterations resulted in three significant impacts: loss of optimal temperature ranges for gonadal development, delayed development and spawning periods, and contraction of suitable temperature windows. These changes pose a substantial threat to successful reproduction.
Meanwhile, analysis of pre-spawning conditions reveals consistent thermal patterns across different spawning events. The 25-day period preceding spawning shows characteristic temperature fluctuations, with a standard deviation of 2.87°C and a range of 0.89°C. These predictable fluctuations appear to serve as a necessary trigger for spawning behavior. However, a notable shift occurred around 2016 in the river's thermal fluctuation patterns during October and November. Key variability metrics showed substantial reductions: standard deviation decreased, amplitude diminished, and both fluctuation frequency and diurnal variation declined by over 50%. This damping of natural temperature variability may critically exacerbate the mismatch between altered river conditions and the species' reproductive requirements.

Chinese sturgeon, water temperature, natural reproduction, spawning delay, hydrological rhythm, human impact