Abstract
Age composition is an important population parameter for understanding and managing endangered species. There are very few studies involving cetaceans in estimating the age of individuals in the wild. In this study, we rigorously quantified the body color pattern of 37 stranded Indo-Pacific humpback dolphins (Sousa chinensis) of the Pearl River Estuary (PRE), which showed a significant, albeit with variability between individuals, correlation with age for both the males (between age 1 and 35, r2 = 0.84) and females (between age 1 and 25, r2 = 0.85). The population-averaged correlation (r2 = 0.85) was then applied to a large volume of photo-identification data (2011–2015) to estimate the age composition of the population occurring in the greater deltaic region, which further suggested a spatial difference in age composition and, therefore, a complex demographic process of the humpback dolphin across the region. In particular, the age composition of humpback dolphins in the east PRE (Lingding Bay) is severely aged. Finally, a population viability analysis with the consideration of observed age structure and the simulated age-specific fecundity suggested that 95.75% of the Lingding Bay humpback dolphins are projected to be lost after three generations. Given the sophisticated anthropogenic landscape in the PRE, we suggest that management units of the humpback dolphins should be clearly defined and the regional-specific conservation measures are much needed.
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05 August 2020
The author would like to correct the formula in the publication of the original article.
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Acknowledgements
This study was supported by the Natural Science Foundation of China (no. 41576128), the Provincial Natural Science Foundation of Guangdong (2017A030308005) in China, the Ocean Park Conservation Foundation of Hong Kong (AW04.1617, MM01.1718), the Biodiversity Investigation, Observation and Assessment Program (2019-2023) of Ministry of Ecology and Environment of China (no. 9-38-27-1), and the Natural Science Foundation of Guangdong Province (2018A030313870). Photographic data of free-ranging dolphins was collected in collaboration with University of Hong Kong and Cetacea Research Institute-Hong Kong, and partially supported with Research Grants Council (RGC) of Hong Kong grant HKU17100015 and Marine Ecology Enhancement Fund (MEEF) grant MEEF2017015 and MEEF2017015A awarded to Dr Leszek Karczmarski. We thank Dr L. Karczmarski and Dr. Stephen C.Y. Chan of Cetacea Research Institute for their various help throughout this research project. We thank the teams of Chinese White Dolphin National Nature Reserve of Guangdong Pearl River Estuary and Chinese White Dolphin Nature Reserve of Guangdong Jiangmen for sample collection.
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Guo, L., Lin, W., Zeng, C. et al. Investigating the age composition of Indo-Pacific humpback dolphins in the Pearl River Estuary based on their pigmentation pattern. Mar Biol 167, 50 (2020). https://doi.org/10.1007/s00227-020-3650-x
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DOI: https://doi.org/10.1007/s00227-020-3650-x