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The Hidden Pearl in Hong Kong Waters – Finless Porpoise

Originally published in Green Country, Issue 132 (Jun 2018)
Author: Green Power

We may all be familiar with the lovely-looking Chinese White Dolphin (Sousa chinensis) which was also the mascot of Hong Kong's handover to China. There is in fact another lesser-known cetacean species that inhabits Hong Kong waters — the Indo-Pacific Finless Porpoise ( Neophocaena phocaenoides ). The porpoise is shy and difficult to spot with its greyish black body lacking a dorsal fin. The much overlooked species may not be as charismatic as the pink dolphins, yet also deserves our attention!

The Finless Porpoise belongs to the family Phocoenidae, members of which are usually smaller than other cetacean species. An adult Finless Porpoise grows up to less than 2 metres. Another major difference lies in teeth shape — Finless Porpoise has spade-shaped teeth while dolphin has cone-shaped teeth. Finless Porpoise also lacks the elongated rostrum and dorsal fin of the Chinese White Dolphin.

The Indo-Pacific Finless Porpoise, as its name indicates, is mainly found in the tropical coastal waters of the Indian Ocean and the West Pacific Ocean. In Hong Kong, they can be found in the eastern and southern waters including by the Soko Islands, Shek Kwu Chau, Lamma Island and Po Toi. Local fishermen show respect for the rather cryptic and elusive species and give it the name "black taboo". Sometimes the species is also called "sea swine" for its resemblance to a pig as it rolls near the water surface for breathing.

Threat of extinction

The Finless Porpoise is listed as "vulnerable" in the International Union for Conservation of Nature (IUCN) Red List. Unfortunately there is still no marine reserve set up for the protection of the species and its habitat. The Southwest Lantau Marine Park is expected to be set up in 2019, when the marine park of Soko Islands—which had been proposed for nearly 20 years—and another one for the mitigation of Shek Kwu Chau reclamation work will be combined.

There are occasional stranding cases of the Finless Porpoise in Hong Kong. Most of the stranded bodies have wounds caused by being entangled in fishing nets or vessel strikes. Apart from the threats from fishery bycatch and vessel strikes, coastal reclamation works have also greatly reduced the habitats of the species. The soon-to-be-built Shek Kwu Chau Integrated Waste Management Facilities, and the proposed East Lantau Metropolis and artificial island at Cheung Chau South, are all located near or in the major habitats of the Finless Porpoise. In addition to direct loss of habitats, reclamation works will also intensify pollution and noise in the waters, impose a high concentration of pollutants on the porpoise population and affect their echolocation ability. They are facing serious threats to their survival in Hong Kong waters!

There are seven species in the family Phocoenidae, including the Vaquita (Phocoena sinus) and Yangtze Finless Porpoise (Neophocaena asiaeorientalis ssp. asiaeorientalis) which are now critically endangered. The former is endemic to Mexican waters, and is often miscaught due to its similar body size to Totoaba (Totoaba macdonaldi), which is poached for its swim bladders — a delicacy in Chinese cuisine. The Vaquita population numbers less than 30 today. The Yangtze Finless Porpoise, the only freshwater porpoise that lives in Yangtze River and a subspecies classified by genetic taxonomic study in 2011, is also on the brink of extinction due to coastal development and overfishing.

The situation of Indo-Pacific Finless Porpoise in Hong Kong may be less perilous today. However, if we fail to work on its conservation, the species may disappear from local waters one day!

Image
© Samuel Hung Ka Yiu
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When surfacing, the Indo-Pacific Finless Porpoise looks like a rolling tyre.
© Samuel Hung Ka Yiu
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Studying the porpoise from a distance in the sky or on land can reduce the impact on the species while observing its natural behaviour.
© Samuel Hung Ka Yiu
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The Indo-Pacific Finless Porpoise has a broad back with numerous tubercles.
© Mandy Cheung
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A locally found stranded porpoise. Wounds can be seen on its head, and were probably caused by entanglement in a fishing net.
© Samuel Hung Ka Yiu
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Shek Kwu Chau waters are important habitat of the Finless Porpoise in Hong Kong
© Taison Chang

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