Helicopter survey is regularly conducted. Researchers use helicopter to search for dolphins in a large area within a relatively short period of time. When researchers sight a group of dolphins, time, location and abundance are recorded.

Helicopter survey can provide better and more comprehensive information on the distribution of dolphins in Hong Kong compared to vessel survey and land-based observation.

Due to the high cost involved, helicopter (aerial) survey is not used to collect systematic transect data. Instead, it is used to carry out distributional study on the humpback dolphins and the finless porpoises, especially in remote areas (i.e. Lamma, Po Toi, Ninepin, Sai Kung, Mirs Bay and Deep Bay) that are relatively inaccesible by vessel.

Photo Identification

When the researchers sight a group of dolphins, they will take pictures of them in an attempt to identify individuals (also known as photo-identification). Their identifying features include permanent external characteristics, such as nicks and scars on dorsal, or permanent marks on the body. Currently, over 400 individual dolphins have been identified in Hong Kong waters and the Pearl River Estuary.The photographic documentations of individual humpback dolphins will be used to study their home ranges and movement patterns. Moreover, the data can be used to clarify some life history parameters to estimate dolphin population abundance through mark / recapture analysis using the computer programme CAPTURE.

The nomenclature of the identified dolphins consists of two parts, the first part consists of two letters indicating where they have been first recorded such NL – North Lantau; SL – South Lantau; EL – East Lantau; WL - West Lantau; CH – Chinese waters; DB – Deep Bay; and the second part consists of number according to their sequence of identification.

The name “Curly”, “Ringo” or “Square fin” are named with accordance of their features but they also have their binomial nomenclature as NL111, NL11 and NL24 respectively.

Land-based survey

Dolphin-watching activity appeared in Hong Kong since the mid-1990s with at least one commercial operator and several NGOs. Such activity has been expanding a lot since the Chinese white dolphin was chosen as the official mascot of Hong Kong's handover to China in 1997. And as a result, more and more people wanted to have a look at the dolphins. In order to know more about the effect of dolphin-watching activities on the Chinese white dolphins, land-based survey has been carried out.

For this study, land-based surveys have been conducted on waters where the Chinese white dolphins frequent, including the Sha Chau and Lung Kwu Chau Marine Park, waters off Sham Wat and Tai O to collect more information about the behaviour of the dolphin with/ without boat, dive time of the dolphin with/ without boat and how the dolphins have been affected by dolphin watching vessels.

Land-based observation is used because it is easier to survey the entire study area instantly from a higher elevation and can get a sense of broader and general view of the interactions between the dolphin and the boats and also the researchers' presence is unlikely to affect the dolphin's behaviour.

Dolphin researchers go to the observation site and scan the water surrounding the observation point with binoculars and naked eyes. Once a group or individual was located, dive time of dolphins, behaviors, surrounding environment and the weather conditions are recorded.

Stranding Investigation

After receiving stranding report, a research team will immediately be dispatched by the AFCD to the stranding location for data and sample collection, which are used for further analysis.

Upon arrival, research team members will start to investigate the carcass. They will identify its body features and species, and take photos of it for record. If the carcass is still fresh, AFCD might take it back to laboratory for more detailed necropsy. If it is rotten already, the investigation team will take data and samples from the carcass on-site.

During necropsy, body length of the dolphin will be measured first. Afterwards, a series of samples will be collected, including skin (for stock structure study), teeth (for age determination), blubber, liver, kidney (all three are for ecotoxicological study), stomach (for feeding habit analysis) and skull (for stock structure study and educational display). Lastly, they will try to find out its sex. From the necropsy, researchers can learn more about the life history and try to figure out the cause of death of the animal.

Biopsy Sampling

The long-term research programme on the Chinese white dolphin in Hong Kong began in late 1995. Enormous progress has been made in learning about the biology of this population of dolphins, but some aspects of their biology have remained elusive. In particular, those aspects that rely on sampling of specimens (e.g. population demographics, life history, reproduction, and effects of contaminants) are still poorly known, due to the fact that the vast majority of available specimens are strandings that are very badly decomposed. In 2004, a tecnique, biopsy sampling, which has already been applied worldwide, was introduced in Hong Kong for sampling the Chinese whtie dolphins. This technique enables the researchers to get tiny samples from wild live dolphins and hence more accurate data.

The researcher is going to shoot a biopsy dart to the dolphin to get its sample

Biopsy sampling can be conducted along with the regular dolphin boat surveys. When dolphins are sighted during the survey, the survey team approaches and observes the dolphin for some time. If any recognizable individuals are seen, and the group's behaviour is suitable, researchers attempt to collect biopsy samples from them. Trained researcher uses a crossbow with specifically designed arrow and dart. Shots are typically taken at target distances of 8-20 m. Upon touching a dolphin's body a tiny sample of the dolphin's skin and blubber is taken at the tip of dart and the arrow then bounces off into the water. Researchers then collect the arrow with the dart and can get the biopsy samples. At the same time, basic data of each biopsy attempt were taken, whether successful or not. And, photographs and video documentation were collected for all biopsy attempts.

The samples collected this way provide much valuable information on the dolphin biology. The skin samples, containing DNA, are used to find out gender of the sampled animals. And the blubber samples are used to determine reproductive hormone level and organochlorine contaminant concentrations, which reveals reproductive status and contaminant levels of the sampled dolphins respectively.

EL01- one of the sampled dolphins in the biopsy sampling trial programme

Also, photo-identification technqiue allows the researchers to make some useful conclusions regarding the progress of the dolphin would healing, and the potential for long-term disturbance from the sampling procedure. As the researcher involved has to be well-trained and the dart used is specifically designed, usually the procedure of bioply sampling only startles the sampled dolphins, but does not pose any harm to the animals.

In 2004, Hong Kong Dolphin Conservation Society funded the first ever biopsy sampling trial programme on the Chinese white dolphins in Hong Kong. For more details, please refer to our page of Research Projects.