Chinese White Dolphin Population Overestimated? True Population Size of White Dolphins in Eastern Leizhou Peninsula Revealed in New Study

In recent years, the habitat of the Chinese white dolphin (Sousa chinensis) has been severely disturbed by the rapid growth of coastal economic activities, causing this species to face an existential crisis. Despite being listed as "vulnerable" by the IUCNRedlist, the scientific community's understanding of its population size and dynamics has limitations and inconsistencies. A new study published in the Marine Mammal Science by the Institute of Deep Sea Science and Engineering of the Chinese Academy of Sciences and several scientific research institutions provides key data on the Chinese white dolphin population in the eastern Leizhou Peninsula.

 



The study lasted five years and used photo identification and capture-recapture techniques to assess the survival probability and population size of the Chinese white dolphin. The study found that the annual survival probability of adult individuals ranges from 0.942 to 0.961, while the survival probability of young individuals is relatively low, ranging from 0.787 to 0.837. In terms of population size, the non-cub population numbers from 2020 to 2023 were 479, 458, 481, and 446 individuals respectively, which were significantly lower than the estimated value of approximately 1,500 individuals in earlier studies, indicating that the previous population size may have been overestimated.

 

The study also found that the transition rate from childhood to adulthood is 25.0%, reaching a peak of 36.0% from 2022 to 2023. Estimates of population size are subject to certain limitations, but revised data indicate that the number of adults is about five times that of juveniles, and the overall population size is stable between 474 and 498. The emigration rate of Leizhou Peninsula white dolphins is extremely low, indicating that this population is highly sedentary and regionally loyal.

 


The significant discrepancy between the study results and estimates from some previous studies may stem from underestimation of capture-recapture rates and flaws in survey design in earlier studies. This study ensures the accuracy of population size estimates through higher catch-recapture rates and improved survey methods. The research team emphasized that although the population size has been overestimated, the Chinese white dolphin population in the eastern Leizhou Peninsula is still the second largest known population of this species, and its ecological and conservation value cannot be ignored. But population data suggest the species is facing a significant decline.

 

The study recommends strengthening the control of human interference in coastal areas, establishing a long-term monitoring mechanism, and further improving protection policies through higher-precision research methods. In addition, the study found that population survival probability and dynamic trends are closely related to human activities. Especially during the COVID-19 epidemic, human activities along the coast decreased and the survival status of dolphins fluctuated to a certain extent. However, as economic activities gradually resume in the post-epidemic era, human interference with their habitats may further intensify, posing a new threat to the long-term survival of the population. The study provides detailed scientific basis for the current status of the Chinese white dolphin population in the eastern Leizhou Peninsula, provides data support for assessing the species' endangered risk, and points the way for the formulation of conservation strategies. The research team calls on relevant departments to take practical measures, combining scientific research and practical actions, to jointly protect the future survival of this endangered species and the ecological health of its habitat.

 

 

Original Chinese Article: https://mp.weixin.qq.com/s/a6Mk6Ohskf0owHugCuWKMQ

Translator: Sara

Reviewed by: Richard

Editor: Sara    

Contact: v10@cbcgdf.org; +8617319454776





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