POPULATION REDUCTION OF THE CHINESE WHITE DOLPHINS IN LINGDING BAY SINCE THE RAPID URBANIZATION OF THE PEARL RIVER DELTA

The Chinese white dolphins (CWD) from the Lingding Bay (LB) are known as one of the most anthropogenically impacted cetacean populations in the world. Since the 1900s, multiple independent research have been conducted on this population using different techniques such as line transect survey, static life table analysis, and capture-recapture modeling. Though it was generally accepted that the LB Chinese white dolphins were highly susceptible to population reduction, there has been a long debate about their current population condition. The uncertainty in demography data hinders accurate extinction risk assessment, effective allocation of conservation resource, and development of efficient conservation strategies. Here, we summarize the demographic information on LB Chinese white dolphins from the past two decades (including estimates of population size, abundance, and annual declining rate), to assess the impact of survey design on the study outcomes, interpret the ecological significance of demographic estimates, and evaluate the robustness and comparability of these estimates. By comparing the representative demographic parameters obtained at different periods, we showed that the LB Chinese white dolphins have experienced a 47.7% reduction in 1998—2015, with the annual declining rate of population has accelerated from 2.2% at the beginning to 6.3% in recent years. Given the extensive urbanization of their estuarine habitat, conflict between dolphins’ persistence and human development appears unavoidable. Through reconstructing the demographic trajectory of LB Chinese white dolphins, we emphasize the urgency of conservation action and the importance of long-term monitoring program.