Learn about the Dolphins
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There are 81 currently recognized species of cetaceans whales, dolphins, and porpoises. Cetaceans are mammals, meaning they have hair (though you might have a hard time finding it), bear live young and suckle them, are warm-blooded, and breathe air with lungs.
While people divide cetaceans into whales, dolphins, porpoises, and blackfish according to size and superficial resemblances, the most important scientific distinction is between the suborders Mysticeti (baleen whales) and Odontoceti (toothed whales). All dolphins and porpoises are odontocetes, though they belong to a number of different families: Delphinidae (oceanic dolphins), Iniidae (Amazon River dolphins), Pontoporiidae (Baiji and Franciscana dolphins), Platanistidae (Indus and Ganges River dolphins), and Phocoenidae (porpoises). These families are further divided into genera and species.
Dolphins
Jaap van der Toorn has an excellent guide to basic dolphin information on his website: HERE.
Sousa chinensis, or the Indo-Pacific Humpback Dolphin, is a coastal dolphin found from South Africa to China and northern Australia. Compared with other species of dolphin, it is not very well studied. Sources differ on basic facts, such as colouration, and whether or not they're found in the Philippines. In fact, until recently they were considered to be several different species. Here are some websites with information about Sousa chinensis:
Jaap van der Toorn's Sousa information -- very good
WWF Chinese White Dolphin Background Information
The Pearl River Delta population
Introduction
The Pearl River joins the sea between Hong Kong and Macau, after draining an area holding roughly one-eighth of China's population. It is a very muddy river, and the delta is very wide. Sousa chinensis has been here probably longer than humans. The oldest known site of human habitation in Hong Kong, in fact, is the remains of a fire in which dolphin bones were found. They are mentioned in Tang Dynasty poetry, and were described and named by Osbeck in 1765.
Sousa chinensis along the Chinese coast looks very different from its cousins in Africa, Australia, and India. Here they are born almost black, quickly fade to light gray, then the gray color gradually disappears, leaving gray spots or patches on a whitish pink background. The Chinese dolphins don't have the pronounced humpback of their African relatives, but their dorsal fin is slightly larger, more similar to a bottlenose dolphin's dorsal.
In the two centuries since Osbeck, Hong Kong seems to have forgotten about the dolphins, until the early 90s, when construction of the new airport at Chek Lap Kok began. The airport construction involved reclamation of nine square kilometres of seabed, at the time the largest single reclamation project in the world. Campaigners at World Wide Fund for Nature Hong Kong brought media attention to the plight of the dolphins. Soon the Hong Kong Government provided funds for research, and several students at the Swire Institue of Marine Science began studying them.
Other scientists started looking at them, bringing more media attention. Hong Kong Dolphinwatch started running tours to see them, a children's book was written about them, and by 1997 they had become the official mascot of the change-of-sovereignty ceremonies. For a few months dolphin images were everywhere. Still, many people in Hong Kong don't realize that the dolphins are real, that they're still alive, and that they're in danger.
Population
Population estimates have been made using two methods, line transect surveys and photo-ID. Unfortunately most research efforts have been limited by political and financial reasons to Hong Kong waters, comprising approximately one-tenth of the total range for the Pearl River Delta population.
Dr. Thomas Jefferson's 1998 Final Report gives the following estimates. Abundance (estimated number of dolphins in Hong Kong waters at any given time), varies from 85 dolphins in the spring to 163 in the autumn. Population (number of dolphins using Hong Kong waters as part of their habitat) was estimated at 448-743. The preliminary estimate of population for Hong Kong and Pearl River Estuary waters (not including the areas west of Macau) is 1,054.
Dr. Lindsay Porter, in her 1998 thesis, gives a population figure of 128 for Hong Kong waters in the winter of 1995-6. No estimate is given for abundance, and no research was done outside Hong Kong waters.
Trends
Jefferson's study covered the winter of 1995-6 to the spring of 1998. Abundance in the North Lantau area during this time appeared to drop dramatically in the winter of 1996-7, then partially recover the following summer and autumn. He explains, "This time period corresponded to the period immediately following the intensive percussive piling work on the Aviation Fuel Receiving Facility (AFRF) for the new airport. It is probable that dolphins may have avoided this area after the loud noise associated with the piling work, thereby resulting in an overall decline in the number of dolphins in the North Lantau area." (p. 31). However, they didn't all come back. Overall, the data show an annual decline in abundance of 27.4%. He could not say, however, with available data, whether this decline was due to mortality or temporary displacement. In a discussion of mortality rates (p. 59-61), he concludes that "At this point there is really little that can be said with any confidence. Taking a conservative approach, it should be noted that there is some evidence to suggest that the current level of mortality that this population is experiencing may be unsustainable." (p. 61).
Porter infers a minimum annual population decline of 3.1%, based on birth rate and death rate. No explanation is given of how the birth rate was determined, however, and it is assumed that all strandings in Hong Kong are from the population using Hong Kong waters, and have not floated in from elsewhere. Her stranding data also differ from Jefferson's (15 strandings for 1996 versus 11).
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The table above shows the number of dead dolphins found and reliably documented within Hong Kong waters (sources: Jefferson 1998, AFCD). This should be treated as a minimum number, as a dead dolphin could easily escape notice. We know of several instances of dolphins being counted only because of coincidences, and several other instances of dead dolphins seen but not counted because they were not photographed and scientists couldn't reach them in time. On the other hand, we may be counting dolphins that have died elsewhere in the Pearl River Delta and have drifted into Hong Kong waters. Low numbers prior to 1993 may be due to the fact that no one felt any particular need to count them, and there were fewer observers then. Many of the deaths in '93-'97 were called in by workers on the Chek Lap Kok airport site.
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More to come . . . .
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Threats facing the pink dolphins
Pollution
Every day, Hong Kong produces 2 million tonnes of liquid waste, and 22,500 tonnes of solid or semi-solid waste. 70% of this is untreated.
About 450,000 cubic metres of raw, semi-processed sewage is dumped into the harbour every day, enough to fill 200 Olympic size swimming pools.
Tributyltin (TBT), an anti-fouling agent that affects the immune system of dolphins, enters the water from floating drydocks off the north shore of Lantau.
The Pearl River brings down industrial effluent, municipal waste, and agricultural runoff from a large area of China.
Dredging and dumping projects stir up contaminated sediments from the sea floor.
Organochlorines such as PCBs and DDT are present in the food chain.
Habitat Loss
Construction of the new airport at Chek Lap Kok involved reclamation of 9.5 square kilometres of prime dolphin habitat.
The North Lantau Expressway, linking the airport to the rest of Hong Kong, required further reclamation of many square kilometres, most of it shallow water and untouched coastline
The river trade terminal between Tuen Mun and Castle Peak Power Station, sits on land reclaimed in 1999 and 2000.
Hong Kong Disneyland was built on a large piece of relaimed land in Penny's Bay. It also involved substential reclamation along the coastline for the road network and the Disney train station and carpark in Yam O. Expansion has been planned for this world's smallest Disneyland, which means more marine habitat will be turned into land.
More land will be reclaimed along the North Lantau coast to make room for housing, roads, and commercial development
Lung Kwu Tan, the bay north of Castle Peak Power Station, will be reclaimed for more container terminals.
Overfishing
There are very few controls on the fishing industry in Hong Kong. Hong Kong's fishing catch has been declining since 1989. Most of the fish caught in the western harbour are not big enough, or the right species, to be sold. They are what is called "trash fish", and are ground up and fed to other fish, in mariculture areas or fish ponds.
Boat Traffic
The Urmston Road shipping channel, between Lung Kwu Chau and Castle Peak Power Station, carries over 70 boats an hour during the day (Mak 1996). Aside from the danger of direct collision, boat engine noise probably interferes with the dolphins' ability to echolocate and communicate with each other.
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Jefferson, Thomas A., Population Biology of the Indo-Pacific Hump-backed Dolphin (Sousa chinensis Osbeck, 1765) in Hong Kong Waters: Final Report, Ocean Park Conservation Foundation, Hong Kong, 1998.
Mak, S. W. "Marine Traffic in Hong Kong" in Proceedings of a Colloquium for Development of a Management Strategy for Chinese White Dolphins, Agriculture and Fisheries Dept., Hong Kong, 1996.
Porter, Lindsay J., The Taxonomy, Ecology and Conservation of Sousa chinensis (Osbeck, 1765) (Cetacea: Delphinidae) in Hong Kong Waters, Ph.D. thesis submitted to The University of Hong Kong, 1998.
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