Study launched to monitor dolphins' health

The Agriculture, Fisheries & Conservation Department recently began a two-year study to monitor the number of Chinese white dolphins in Hong Kong. They will take tissue samples from live dolphins to investigate the long-term impacts of environmental contaminants on the health of the mammals.

The department's Senior Marine Conservation Officer, Joseph Sham said that monitoring the Chinese white dolphin has been an important part of the conservation of marine mammals in Hong Kong. The department has been studying the population and biology of this rare animal for the last 10 years to protect them from the threat of pollution, development and other human activities. Sham said information on the dolphin population and its trends are vital to their conservation and adaptive management and is also an important indicator to assess the effectiveness of the conservation programme.

The programme aims to investigate the causes of mortality such as the long-term impacts of environmental contaminants on dolphin health. Chinese white dolphins are also known as Indo-Pacific humpback dolphins and are found in coastal waters and estuaries throughout the Indian Ocean and western Pacific Ocean. Their range extends from South Africa in the west to the coast of China and northern Australia in the east. According to recent survey data, there are more than 1,500 dolphins in the whole Pearl River Estuary.

Mr Sham said the number of dolphins residing in Hong Kong waters has been quite stable at about 200. They are mostly found in the western waters, including outer Deep Bay, north, south and west Lantau waters. Dolphin numbers show a slight increase, attributed to the improved general marine environment and the conservation programme the department has adopted, he added. In the past, the department only tested tissue from dead dolphins found stranded on the coach for contaminants. To better gauge these pollutant levels and understand the animal's biology, it recently started taking samples from live dolphins following a successful trial last year.

Researchers use a crossbow to shoot a biopsy dart which takes a tiny core of skin and blubber from the live dolphin at sea. They use the skin sample to determine the gender, and the blubber helps in pollutant analysis. Dr Thomas Jefferson, the department's hired expert, will collect about 30 biopsy samples in the next two years. The tissues would be tested in collaboration with the City University of Hong Kong. Results will help generate an environmental risk assessment for the Chinese white dolphins in Hong Kong waters.

Mr Sharm said that the department has imposed strict restrictions when taking samples from the dolphins. For example, the researcher cannot take samples in the marine park and no samples should be taken from dolphin parents that are taking care of their offspring. He said the whole process of sampling will be recorded and efforts will be taken to keep the impact on the dolphins to a minimum.

(source: www.news.gov.hk)