As its name suggests, the Indo-Pacific finless porpoise (Neophocaena phocaenoides) lacks a dorsal fin(4), and instead has a ridge that runs down the middle of its back (2). The Indo-Pacific finless porpoise can also be distinguished by its rounded head, which lacks an apparent beak (2). This small marine mammal has a relatively slender body (4), which is dark to pale grey on the upper side and lighter on the underside. Colouration is paler in juveniles, developing into an almost black colouration in mature adults (2). A scattering of horny tubercles is found on the dorsal ridge, which may create an anti-slip surface when the female carries its calf on its back. However, it is more likely that the tubercles act as sensory organs, with each tubercle containing numerous nerve endings (2).
The Indo-Pacific finless porpoise is a rather shy and elusive animal (4), which does not form large schools and is most often seen in pairs consisting of a female and its calf or an adult pair (2). It generally swims quietly, rarely leaping, splashing, or riding the bow waves of boats like other small cetaceans(2). This species is an opportunistic feeder, consuming a variety of schooling fishes, squids, octopuses, shrimps and prawns. The finless porpoise itself is known to be preyed on by the great white shark (Carcharodon carcharias) (2).
Very little is known about the breeding biology of the Indo-Pacific finless porpoise. Female finless porpoises are thought to calve every two years, with the peak calving season varying with location. For example, on the Pacific coast of Japan calving takes place in May and June (2). It is estimated that the gestation period of species in the genusNeophocaena around 11 months and that the female feeds the calf for approximately 7 months. The finless porpoises is known to reach sexual maturity at 4 to 9 years of age and lives for up to 25 years (2).
The finless porpoise inhabits tropical and warm temperate coastal waters (4), preferring areas over sandy or soft bottoms, including shallow bays, mangroves and estuaries. It can also be found in some large rivers (2).
The Indo-Pacific finless porpoise’s preference for coastal and riverine habitats makes it highly vulnerable to the impacts of human activities (2). Deforestation of mangrove areas, rampant harbour expansion and the development of shrimp farms all degrade the porpoises’ habitat, increasingly threatening this species’ survival (2)(5). Although the Indo-Pacific finless porpoise is not directly targeted by fishermen, large numbers die when they become entangled in fishing nets, particularly gillnets (2)(5).
Furthermore, high levels of toxic pollutants have been reported in areas inhabited by Japanese populations of finless porpoises, and while species in this genus tend to avoid boats (2), mortalities caused by collisions with vessels may be a problem in busy shipping areas, such as Hong Kong (1)(5).
The Indo-Pacific finless porpoise is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3) and Appendix II of the Convention on Migratory Species (CMS) (6). Suitable management methods are needed to conserve this species successfully (1).
A group comprising all whales, dolphins and porpoises.
Relating to the back or top side of an animal.
The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
The use of an electrical current to temporarily stun fish before they are caught. Also known as electrofishing.
Measures to conserve a species that occur outside of the natural range of the species. For example, in zoos or botanical gardens.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
The state of being pregnant; the period from conception to birth.
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
A small, rounded, wart-like bump on the skin or on a bone.
Reeves, R.R., Smith, B.D., Crespo, E.A. and di Sciara, G.N. (2003) Dolphins, Whales and Porpoises: 2002-2010 Conservation Action Plan for the World's Cetaceans. IUCN, Gland, Switzerland and Cambridge, UK.
Convention on the Conservation of Migratory Species of Wild Animals (December, 2011) http://www.cms.int/
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