Chinse white dolphins - unique to China?

Despite its name, the Chinese white dolphin is not endemic to China. As already mentioned, their correct name is Indo-Pacific humpback dolphin, and as the name suggests, the species can be found in both the Indian and Pacific oceans. They prefer to stay in coastal waters such as estuaries and near wetlands with mangroves. Their distribution is broad and global, extending from the South China Sea in the east, to the eastern and southern coasts of Africa, Middle East, the Indian Ocean in the west, and Australia in the south. Apart from Beihai, Xiamen and the Pearl River Estuary of the People's Republic of China, the species can also be found in Chinmen Islands of Taiwan, Vietnam, Malaysia, Thailand, India, Pakistan in Asia, Australia, and even Iran, Iraq, Saudi Arabia, Bahrain, Kuwait, Qatar, UAE and Oman in Middle East, Mozambique, Madagascar and South Africa in Africa. In 2002, scientists even recorded the first scientific sighting of this species in western Taiwan!

Here is a distribution map of humpback dolphin around the world

Chinese white dolphin is close to extinction?

In the mid-1990s, the media and green groups publicised that the Chinese white dolphins were an endangered species, some even said the dolphins would be extinct in the new millennium! This has obviously been proven wrong now, it is 2006 and there are still hundreds of dolphins in HK.

In the World Conservation Union's Red List of Threatened Species the Chinese white dolphin is classified as “Data Deficient” meaning there is not enough evidence to show whether the Chinese white dolphin species is endangered or not. No surveys are being conducted in many nations where the dolphins are found hence we cannot accurately estimate their numbers.

What about those found dwelling in the Pearl River Estuary? According to latest research, at least 1,400 Chinese white dolphins live in this area with around 300 frequenting Hong Kong waters. In the past eight years, their number has remained stable with no downward trends thus it is misleading to say that the Chinese white dolphins are an endangered species!

But that doesn't mean that we don't need to protect the Chinese white dolphins. Prevention is always better than cure. We should work on conserving the dolphins before it is too late. Only if we join hands now to maintain and improve their living conditions will these elegant creatures continue to thrive in Hong Kong and its neighbouring waters for a vibrant marine environment.

Related Articles: Abundance of Dolphins in Hong Kong drops by 40% ?!

Where do the Chinese white dolphins in Hong Kong mostly occur?

The following red dots are locations where researchers found Chinese white dolphins in Hong Kong

One of the Chinese white dolphin's favourite habitats is near estuaries, such as those in the western waters of Hong Kong where the Pearl River joins the South China Sea. These include waters off north, south and west of Lantau Island, as well as Deep Bay. If you plan to watch the dolphins at sea, don't miss the following hotspots: the Brothers, Sha Chau and Lung Kwu Chau Marine Park, Castle Peak Power Station, Black Point and Tai O. In the summer, you may even try Southern Lantau, including waters off Fan Lau and Soko Islands.

Hanging around with family, or living alone?

You may think that, like us, dolphins are highly intelligent animals and live closely with their friends and relatives. But whilst some dolphin species such as the orca do have intimate relationships with parents, siblings, and even grandmothers, Chinese white dolphins don't. Calves leave their mothers and live alone after being weaned and spend most of their time with a few other individuals when not alone. Also, they may not have fixed partner(s) and often live with different individuals according to studies.

Find it out - Photo-identification

All Chinese white dolphins may look similar to you, but researchers can identify individuals by looking at their dorsal fins – similar to the way we use our fingerprints. As well as having different shapes, the dolphins' dorsal fins bear special features like nicks and wound marks. And apart from the dorsal fin, some dolphins may bear special features on other parts of the body enabling researchers to identify each one.

Some dolphins bear marks that are eye-catching and researchers can identify them at a glance. But in others the characteristics are more subtle and researchers need to take photos of their dorsal fins and carefully examine them before they can be identified. The photos can also be cross-referenced with the photo-ID catalogue to see if the dolphin has been recorded before. More than 300 Chinese white dolphins have been identified in Hong Kong waters and the Pearl River Estuary by photo-identification to date. The information collected helps us to understand more about their home ranges, moving patterns and behaviour.

The following six Chinese white dolphins have already been identified by researchers. Can you find out what kind of identifiable features they bear? Their names might give you some hints.

Playful dolphins

Chinese white dolphins are playful animals. Researchers are tireless of their many tricks even after years of looking at them. Some their common behaviours are:

Dolphin's diet

Most of us know that the Chinese white dolphin's favourite food is fish. In dolphin stomach samples, researchers have found over 20 fish species including Croaker, Lion-head croaker, Thryssa and Bomby duck – basically the same types of fish we like to eat ourselves! It seems, however, that they are not interested in cephalopods (like octopus and squids) and crustaceans (like shrimps and crabs).

How long does Chinese white dolphin live?

This is one question many people are interested in. It is difficult to tell the age of a dolphin by its appearance alone and so researchers have to find clues from dolphin carcasses and the teeth are the key to unveil the secret of a dolphin's age. By sectioning a tooth, researchers can estimate the age of a dolphin by counting the number of tooth layers. To date, the oldest Chinese White Dolphin confirmed in Hong Kong is 38 years old, but we believe they can live up to 40 years, just like their South African counterparts do.

A colourful life

Among the some 80 species of whales and dolphins, the group of Chinese white dolphins living along the coast of Southern China undergo the greatest colour changes in their life. Newborns are usually dark grey and about 1 m long. As they become juveniles, the greyness fades and they start to turn pinkish. The original grey becomes numerous spots which gradually disappear. Adult Chinese white dolphins – with withbody lengths of up to 2.6-2.7 m and weights of up to about 250 kg – are mostly pink with only a few spots.

Most people are astonished by the bright pink colour of the Chinese white dolphins during their first encounters. Part of the reason may be the misleading name of Chinese “white” dolphin. So why are the dolphins pink? There are two existing theories. One claims that the bright colour originates from the pink pigments present in the epidermis. The other theory is more reliable and suggests when the dolphins are swimming, the blood vessels near their skin dilate to enable more blood flow for heat release, therefore making the dolphins look pink – similar to flushing in humans during exercise. Researchers have also found that dead dolphins are not pink but milky white which further supports this second theory.

Risks facing the dolphins

Although Chinese white dolphins are not identified as an endangered species, they are living in a place full of dangers. If you visit them at sea, you can see the risky lives they lead.

Loss of home:

70% of the airport land comes from reclamation

Over the past decade, the home range of dolphins in Hong Kong has shrunk substantially because of the construction of the new airport at Chek Lap Kok Island and the associated land reclamation. The accumulative detrimental effects coastal development projects have on the dolphins is significant. Reclamation devastates coastal and benthic ecology, reduces the amount of fish available to the dolphins to feed on.

Dredging worsens water quality

The dredging may also unearth pollutants that have settled on the seafloor causing water quality to further deteriorate. Now that a number of coastal and marine projects, including the well-known Hong Kong-Zhuhai-Macau Bridge and Container Terminal No. 10, are planned, it is worrying that our dolphins will have to continue to cope with all sorts of threats in the future.

Vessel collision :

Hong Kong is a busy harbour with numerous vessels travelling to and fro. North-western and Southern Lantau waters, the home of Chinese white dolphins, are no exceptions. High-speed ferry is by far the biggest threats to dolphins. Urmston Road waterway next to Sha Chau and Lung Kwu Chau Marine Parks is a main route connecting Hong Kong and Nansha of Mainland China. And the waterway south of Lantau Island is the major route for high-speed ferries travelling between Hong Kong and Macau. Dolphins frequent both of these waterways and researchers have witnessed many times how the ferries came close to striking dolphins. We have found some dolphins bearing scars likely to have been caused by vessel propellers. These were lucky to survive, but our guess is that others would have been less fortunate and were killed.

Three of the Chinese white dolphins that were found with propeller cuts

Dolphin watching boat disturbance:

“Ecotourism” has become more popular in Hong Kong in recent years. More and more tour companies, green groups and schools are holding Chinese white dolphin watching tours.

Allowing people to see and appreciate wild dolphins at sea is a good thing but because the activity is not regulated in any way, any type of boats can take visitors out and sometimes they disrupt the dolphins. For example, many dolphin-watching boats chase after the dolphins when they appear and sometimes several boats would encircle one pod of dolphins at once. Research shows dolphins stay away from these irresponsible boats, or choose to dive for longer. In the long term, the dolphins may abandon the area where they have been harassed.

Motorized small boats at Tai O do pose a threat to the local Chinese white dolphins

In the last few years, dolphin watching operators have appeared around Tai O. Knowing nothing about dolphins, the skippers of these boats have been chasing the animals at even higher speeds than the other operators. It is likely that the greater the speed the boats chase the dolphins at, the great threat they pose to the dolphins.

Water pollution:

There is still no concrete proof that water pollution impinges directly on dolphins' health. Yet samples collected from dolphin carcasses in Hong Kong reveal high concentrations of organochlorine and heavy metals suggesting that these pollutants are harmful. Pollutants are washed into the sea from local discharges and the Pearl River. The high concentration of pollutants accumulated in dolphins' blubber or internal organs might be attributable to its polluted food source which contains non-degradable toxic substances. At the same time, a lot of pathogenic bacteria and viruses can be found in Hong Kong waters, thus making them even more vulnerable to diseases which can be fatal in some cases.

Underwater noise:

Underwater piling

Tranquillity is a luxury for Chinese white dolphins in Hong Kong! The underwater world they dwell in is noisy with scores of vessels and boats travelling around, as well as coastal underwater works (particularly underwater percussive piling). As dolphins rely on their hearing for echolocation and communication with companions, a deafening environment might affect its ability to locate food and communicate and in serious cases cause permanent damage.

Fishery bycatch:

In 1997, a Chinese white dolphin was found entangled and drowned in a fishing net

A favourite feeding strategy of the Chinese White Dolphins is following fishing vessels for fish escaped from the nets. The dolphins like to follow pair trawlers, which catch the most fish and stir up fish at the sea bottom, but by doing so, they risk being entangled by the fishing nets. As dolphins have to surface to breathe, they will drown once entangled. Gill-net is another threat to dolphins in Hong Kong. However, fishery by-catch is not a serious menace to Chinese white dolphins in Hong Kong. It is observed that they are skilful enough to avoid getting entangled when following the trawlers.

What has Hong Kong done to protect Chinese white dolphins?

We should grateful that Chinese white dolphins are not near extinction but it doesn't mean we should sit around doing nothing! In recognition of the numerous risks the dolphins are facing in their daily lives, the Agriculture, Fisheries and Conservation Department (AFCD) of the Hong Kong government and some local green groups carry out different measures to protect them, hoping they would continue to thrive in our waters.

Law Protection:

Chinese white dolphins in Hong Kong are mainly protected under two ordinances, the Wild Animal Protection Ordinance (Cap 170) and the Animals and Plants (Protection of Endangered Species) Ordinance (Cap 187), which are both regulated by the AFCD. The Wild Animal Protection Ordinance is in place to protect wild animals and their habitats in the territory. So under this ordinance, harassing, harming, capturing or killing Chinese white dolphin is illegal.

The Animals and Plants (Protection of Endangered Species) Ordinance gives effects to the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES) to prevent any illegal export, import and sales of endangered species and its body parts. The Chinese white dolphin is listed in Appendix I of CITES, which means any trade of Chinese white dolphins for commercial purpose is strictly prohibited worldwide.

Establishment of Dolphin Reserve:

Sha Chau & Lung Kwu Chau Marine Park

Up till now, the AFCD has established four marine parks in the territory with Sha Chau and Lung Kwu Chau Marine Park to the northwest of Lantau Island set up for the protection of Chinese white dolphins. Under the Marine Parks and Marine Reserves Regulation, all vessels must limit their speed to 10 knots in the marine parks to avoid bumping into the dolphins. At the same time, trawlers are prohibited to operate in the marine parks so to protect the fish stock in the areas and eliminate the risk of fishery bycatch.

Research:

Long term research and monitoring is crucial to dolphin conservation, by which researchers can learn more about the ecology, status, as well as trends and changes in abundance and distribution of the dolphins. For example, if dolphin abundance plunges dramatically in a year, researchers can detect it right away, find out the cause and hence implement remedial measures.

In addition, information collected from dolphin carcasses further enhances our understanding of their status. For instance, their liver reveals the amount of toxic heavy metals accumulated, which can help researchers work out how environmental pollution directly affects the dolphins.

Education:

Education is a vital part of dolphin conservation! The efforts spent by the few conservationists and the government will go in vain if public recognition and support is lacking! That's why the government and some green groups regularly hold talks, exhibitions and contests for schools and organizations, and publish different kinds of dolphin booklets and posters in order to prompt public awareness of the dolphins and their conservation. Also, the government and some conservation groups like us, the HKDCS, have websites to provide the public and students with lots of useful information about the dolphins.

Public awareness activities held by the HK Dolphin Conservation Society, including seminars, dolphin watching trips and exhibitions etc.