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Dolphins and porpoises of Hong Kong

Indo-Pacific humpback dolphin (locally known as the Chinese white dolphins)
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This group of dolphin is commonly called the “Chinese white dolphins” in Hong Kong and Mainland China. Scientists called them Indo-Pacific humpback dolphins (Sousa Chinensis).
In the Pearl River Estuary, the dolphin population consists of over 1400 members. They swim to and fro in the Hong Kong and Mainland waters. There are 88-145 dolphins in Hong Kong waters.
(The original map was downloaded from Agriculture, Fisheries and Conservation Department, Hong Kong)

Apart from the Pearl River Estuary, Indo-Pacific humpback dolphins live along the coastal waters of the India Ocean and western Pacific Ocean, including southern China, Thailand, Australia, South Africa, etc. However, their colour may be different from the dolphins in Hong Kong.
Chinese white dolphins eat fishes that can be found at river mouth, including croakers, lion-head fishes, mullets and anchovies. They sometimes follow fishing boats in large group to feed, while they sometimes feed on their own. Younger dolphins follow mothers to find fishes.

New born Chinese white dolphins are about 1.5m long. They are in dark grey.

When the baby grows older, it will become light grey with a touch of pink.

The grayish body of the little dolphin will bear spots. These spots will disappear when it grows older.

Adults are around 2.5m long. They are pinkish and yet, some may still bear spots.

Finless porpoise
Finless Porpoise (Neophocaena phocaenoides) belongs to the porpoise family. It is another kind of dolphins of Hong Kong. Finless Porpoises can be found in southern and eastern waters of Hong Kong.
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Though finless porpoises and Chinese white dolphins are neighbours in Hong Kong waters, they seldom appear in the same area at the same time. In winter and spring, finless porpoises mainly occur in the southern waters of Hong Kong. During summer and autumn, they can be found near the waters of Po Toi, NinePins, outer Sai Kung sea and Mirs Bay.

It is easier to find finless porpoises in spring because about 152 of them would be in Hong Kong waters. In summer, only about 55 of them would be in Hong Kong waters.
The two oldest finless porpoise stranded in Hong Kong are of 28 and 33 years old.
Fineless porpoises love coastal fishes like anchovies and cardinal fishes as well as squids.

How do Finless Porpoises differ from Chinese white dolphins?
As suggested by their name, finless porpoises have no dorsal fin. Instead, they have lines of denticles on their back.
They do not have a long beak as the dolphins. Their teeth are spade-like. Chinese white dolphins have a long beak and their teeth are sharp.
Skull of Finless porpoise; Skull of Chinese white dolphins
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While Chinese white dolphins love fishes at the river mouth, finless porpoises love fishes and squids of the ocean. This may explain why the porpoises live in southern and eastern waters of Hong Kong, which is further away from the Pearl River mouth.
Finless porpoises are smaller than Chinese white dolphins. New born porpoises are about 70-80 cm long, while adults are only up to 1.6m long. They grow rapidly in their first year, and after that, their growth rate slows down.
They become sexually mature at an early age, with males becoming mature at around 4-5 years old and females becoming mature at around 5-6 years old. Female porpoises can mate and become pregnant soon after giving birth. Most porpoises are born in late autumn to early winter.

For details on dolphins of Hong Kong, please refer to the website of the Hong Kong Dolphin Conservation Society: www.hkdcs.org