Low Survivals and Rapid Demographic Decline of a Threatened Estuarine Delphinid

Beibu Gulf’s (BBG) Indo-Pacific humpback dolphins present both a genetic differentiation and phenotypical differences from conspecifics other areas of the South China Sea. Given recent urbanization industrialization in southern China, BBG warrant conservation attention. However, this population’s demographic trend is unclear, making it hard to take measures. To assess population status BBG, photo-identification surveys were conducted between 2015 2019 inshore region surrounding Dafeng River Estuary, which represents most urbanized industrialized coastal area region. Robust design modeling suggested constant survival for female adults (0.89, 95% CI: 0.83–0.94). In comparison, juvenile sex-undetermined dropped 0.92 (95% 0.75–0.98) 0.86 0.71–0.94) 2016 bounced back 0.89 0.80–0.94) 2018. The low level may justify rapid decline annual size 156 133–184) 102 98–107) 2019. We found little impact emigration on dolphin process. Instead, fluctuating survivals, although with overlapping confidence intervals, seemingly presence strong marine stressor(s). Our study highlighted that obtaining high-resolution data essential improving our understanding dynamics. Moreover, anthropogenic stress should be quantitatively studied temporal spatial perspectives, help depict ecological response activities.