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Finless Porpoise

 

Finless Porpoise

Finless porpoises are widely distributed in the coastal waters of Asia, from the Persian Gulf, east and north to Central Japan and as far south as the northern coast of Java and the Strait of Sunda (see map). Finless porpoises are described as a coastal, estuarine or riverine species and they are usually sighted near the coast.

Finless porpoise (Neophocaena phocaenoides)

Natural History
Finless porpoises are slender and have no dorsal fin. In its place along the mid-dorsum is a low dorsal ridge which is covered by thick denticulated skin. Newborn finless porpoises are mainly black with some grey on the dorsal ridge area. These young porpoises quickly become lighter and after 4 to 6 months attain the uniform light grey colour of adults. Both male and female finless porpoises grow to lengths greater then 1.55 m. Although there is a great deal of variability between populations of finless porpoises, males become sexually mature at 4.5 – 9 years and females at 3-7 years. Finless porpoises are opportunistic feeders, consuming a wide variety of fishes, shrimps and cephalopods throughout their range.


Status and Protection
Finless porpoises are found yearly throughout their entire range, but in some areas exhibit seasonal movements and changes in local abundance. These changes in local abundance and distribution are not well documented for most regions. Finless porpoises are currently listed in the IUCN Red List of Threatened Species as a Data Deficient species throughout their range, except in China where they are currently listed as Endangered.

Threats to the Species
The greatest threat to finless porpoise populations is incidental mortality in fishing gear. These animals are taken in a variety of driftnet, gillnet, trap net and trawl net fisheries throughout their range. The extent of bycatch in many areas is not well documented. They are also caught in “rolling hook” gear (lines of iron hooks set across the flow of the river) in the Yangtze River, China.

Sources
Kasuya, T. 1999. Finless Porpoise Neophocaena phocaenoides. In S.H. Ridgeway & R. Harrison [eds.], Handbook of Marine Mammals, Volume 6: The Second Book of Dolphins and Porpoises. Academic Press. San Diego.

Jefferson, T.A. et al. 1993. Marine Mammals of the World. FAO Species Identification Guide. United Nations Environment Programme. Rome.

Perrin, W.F., Donovan, G.P. and Barlow, J. 1994. Gillnets and Cetaceans. Report of the International Whaling Commission, Special Issue 15. Cambridge.