Abstract
Research on stranded cetaceans in Hong Kong have focused extensively on quantitative and temporal analysis of pollutant burden. Many of them are potentially associated with detrimental effects on health, and in particular, on the reproductive system.1 From 2007, stranding data and material from post-mortem examinations of odontocetes in Hong Kong waters were obtained in order to assess the demographics and health of local populations of threatened cetacean species using a veterinary approach.
Temporal analysis of demographic data was performed to detect trends. The two resident species, the Indo-Pacific humpback dolphin (Sousa chinensis) and the Indo-Pacific finless porpoise (Neophocaena phocaenoides) were the most frequent species found stranded. The Indo-Pacific humpback dolphin’s International Union for Conservation of Nature (IUCN) red list conservation status has recently been reclassified from near threatened to vulnerable.²
Reproductive and mammary tissues, which are often neglected when investigating the cause of death of stranded odontocetes, were included in analyses for this project. In a high proportion of cases, multiple lesions were found. As demonstrated by lesions and pathogens identified, bacterial, viral, and parasitic diseases were documented, some associated with a public health concern. Diseases with a potentially considerable influence on reproductive health and calf rearing were highlighted. Several pathogens were detected and described for the first time in Indo-Pacific humpback dolphins and in Indo-Pacific finless porpoises. Additionally, these were previously unreported in any odontocetes in the South China Sea.
In conclusion, it was shown that reproductive pathologies are among processes that may impact the reproductive success in odontocete species in Hong Kong. This may represent significant threats to populations already impacted by other threats.1 It is essential that disease monitoring plays an integral part in local marine species conservation plans. Additionally, there is a need for combined studies investigating the interactions between demographic and reproductive health parameters and environmental pollution load in odontocetes in Hong Kong waters. Scientists from multiple disciplines need to work together towards conservation of these species declining fast in a heavily and increasingly urbanized part of the world.
Acknowledgements
The authors thank the Agriculture, Fisheries, and Conservation Department, the Government of the Hong Kong Special Administrative Region, for providing access to the animal files and material, the Ocean Park Corporation veterinarians and clinical laboratory staff, as well as the Ocean Park Conservation Foundation scientific officers who were involved in the postmortem examinations. Partial support from the Environment and Conservation Fund for this project is acknowledged.
*Presenting author
Literature Cited
1. Karczmarski L, et al. 2016. Chapter Two - Humpback dolphins in Hong Kong and the Pearl River Delta: status, threats and conservation challenges. Adv Mar Biol 73:27–64.
2. Jefferson TA, Smith BD. 2016. Chapter One - Re-assessment of the conservation status of the Indo-Pacific humpback dolphin (Sousa chinensis) using the IUCN red list criteria. Adv Mar Biol 73:1–26.