Sousa chinensis The Indo-Pacific Humpback Dolphin

This is, according to Wikipedia, “actually from blood vessels used for thermoregulation to prevent overheating from exertion.” These dolphins generally live up to 40 years of age, the oldest currently found in Hong Kong, aged 33. The Indo-Pacific Humpback Dolphin, also called the Chinese White Dolphin, belongs to the Kingdom of Animalia, the Phylum of Chordata, the Class of Mammalia, the Order of Cetacea, the Family of Delphinidae, and the Genus of Sousa. It has a stocky body and a long, clearly defined beak. The name humpback is derived from the hump on which the dorsal fin rests upon; however, it is practically non-existent or not so well defined in some dolphins. Males reach up to 3.2m, females up to 2.5m and the dolphins can weigh up to 284kg. Generally, they are born black, but as the Chinese White Dolphins mature, their colour gradually changes until it is bright pink.

Distribution and Abundance The Indo-Pacific Humpback Dolphins are generally distributed, as shown on the map to the right, along the warm and temperate waters of the Indian and the Pacific Ocean. They are found in many places; from Southern Australia to Southern China and Taiwan. They are known to enter rivers, an example being the Yangtze River, estuaries or deltas (the Pearl River Delta) and even mangroves, seemingly to favour the latter. They also seem to prefer depths no deeper than 20m and warm temperatures from 15ºC to 36ºC. According to the Agriculture, Fisheries and Conservation Department, the amount of dolphins in Hong Kong waters and the Pearl River Estuary numbered 217 during Winter, 78 during Spring, 199 during Summer, 209 during Autumn. Apparently, most of the dolphins were found close to Lantau Island.

Behaviour and Eating Habits Indo-Pacific Humpback Dolphins generally travel in a pod of 3-5 other dolphins. Generally slow swimmers, travelling at the average speed of 4.8kph, they have been known to chase off or kill sharks. They have been known to associate with Bottlenose dolphins and, less commonly, with Finless Porpoises and Long-snouted Spinner Dolphins. They are supposed to be “quite difficult to approach and tend to avoid boats by diving and reappearing some distance away in a different direction.” (Quoted from These dolphins generally feed on reef fish, molluscs and crustaceans. According to the Hong Kong AFCD, at least 20 fish species from 13 different families have been identified, most commonly Engraulidae (anchovies), Sciaenidae (drums and croakers) and Clupeidae (herrings, shads,sardines, menhadens). The most commonly eaten fishes were lion-headed fish, various croakers, and anchovies.

Environmental Threats At the time of 2006, the Indo-Pacific Humpback Dolphin was considered extinct in the Yangtze river. In an article written in 1998, a passage says: The territorial waters of Hong Kong are highly contaminated with anthropogenic pollutants, including trace metals. Hong Kong's population of Indo-Pacific hump-backed dolphins (Sousa chinensis) inhabits an area where a high volume of sewage waste discharge and the close proximity of contaminated mud pits mean a considerable potential for trace metal contamination. Trace metal concentrations in the muscle tissue of fish caught from areas of high dolphin abundance are notable. However, in order to gauge the amount of trace metal consumed by dolphins, whole fish must be analysed. Whole fish from areas of high dolphin abundance have considerably higher trace metal loads than muscle tissue alone. Considering the consumption of prey items by dolphins, a daily intake of trace metals was estimated as As, 410–518; Cd, 34–44; Co, 4–5; Cr, 40–50; Cu, 44–56; Hg, 51–66; Mo, 22–27; Ni, 19–24; Pb, 320–403; Se, and Zn, 388–490 (μg kg −1 body wt. per day). Concentrations of arsenic, chromium, lead, molybdenum and nickel in dolphin tissues were an order of magnitude lower than in prey items, suggesting these elements may be excreted by this species.

Environmental Threats (2) Mercury concentrations in dolphin tissues were, however, an order of magnitude higher than in prey items and could be considered potentially health threatening (max: 906 μg kg −1 dry wt.). Hong Kong's Indo-Pacific hump backed dolphin population has a high dietary intake of trace metals which may, especially in the case of mercury, be a cause for concern. ( 3VCHGWX2D&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_v ersion=1&urlVersion=0&_userid=10&md5=42a3f30d422bd687462e8d9b07 a59f643VCHGWX2D&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_v ersion=1&urlVersion=0&_userid=10&md5=42a3f30d422bd687462e8d9b07 a59f64) 3VCHGWX2D&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_v ersion=1&urlVersion=0&_userid=10&md5=42a3f30d422bd687462e8d9b07 a59f64 Other more obvious dangers include dolphins being tangled up in netting, water pollution, dolphin bycatch, sound disturbances, boat strikes and also reclamation of land, leaving less living space for the dolphins.

Dolphin Conservation There are several dolphin conservation organisations in Hong Kong, perhaps the most dedicated being the Hong Kong Dolphin Conservation Society. They aim to increase public knowledge about the “biology and conservation of Chinese white dolphins and finless porpoises in Hong Kong, and cetaceans in other parts of the world; preservation of dolphins and their habitats in Hong Kong; impacts posed by dolphin-watching activities to dolphin and the importance of raising standard of dolphin-watching industry in Hong Kong; and global issues of whales and dolphins such as captivity, whaling, fishery bycatch and marine pollution”, and also conduct scientific research on the wild dolphins in Hong Kong, Taiwan and China, the education of the importance of dolphin conservation to children, and suchlike. Another organisation, the Hong Kong Dolphinwatch Ltd., more interested in dolphin watching, maintains that dolphin watching is not just good for tourism but also giving public knowledge about dolphins. Others, such as the AFCD of Hong Kong, focus on again dolphin conservation and various exhibitions. Ocean Park aims to conserve wildlife through research and education. Whale and Dolphin Conservation Society is the world’s most active charity dedicated to conservation and welfare of cetaceans, of which whales, dolphins and porpoises belong to.

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