Common Name: Finless Porpoise
(G. Cuvier, 1829)
Finless Porpoise range.
General Description: The Finless Porpoise, like the Irrawaddy Dolphin Orcaella brevirostris, is said to present the appearance of a small Beluga Delphinapterus leucas. It has a small head, with the blowhole on top. The melon is rounded, and there is no beak. The mouthline is curved upwards towards the eye. Behind the blowhole is a slight depression, like a neck crease. The animal enjoys flexibility of this neck, and the head can be rotated freely. Interestingly, this is a facility also enjoyed by the Beluga, which is classified in a different family.
The dorsal fin is completely absent, and an area of the skin behind where the fin should be, is dark and covered with small rounded projections. The Finless Porpoise’s flippers are relatively long with blunt tips. The colour is uniform grey, often with a bluish tinge. The lips and chin of this animal are lighter.
The name ‘Finless Black Porpoise’ was once widely used for this species. This is not very apt, as the porpoise turns black only after death.
Size: Finless Porpoises grow to a maximum length of about 1.9 m. They weigh 30 to 45 kg.
Appearance At Sea: Generally found in pairs, groups of up to 10 Finless Porpoises are sometimes seen. Young calves are said to travel clinging to their mothers' backs.The Finless Porpoise is said to make a chirping sound, this being one of the reasons for its Malayalam name Eleyan eedi.
While breathing they rise so that they just touch the surface with their blowholes. The lack of dorsal fin makes it look as though the back is submerged but it in fact reaches the surface enough to reveal the absence of the fin.
After 3-4 abrupt breaths the porpoises dive for 45-75 seconds, often surfacing around 100m away. They are quick and lively underwater, swimming just beneath the surface with sudden, darting or circling movements.
Finless Porpoises are often found in the company of Indo-Pacific Hump-backed Dolphins Sousa chinensis.
Found In: These porpoises inhabit inshore coastal waters and estuaries, and are said to frequent rivers. They feed mainly on crustaceans.
Records from India: There are many instances of this porpoise being washed ashore or being found in fishermen’s catches, or entangled in gill nets. These are generally single specimens, but up to 17 animals have been caught together. An account of a group of porpoises being driven into a lagoon and slaughtered in the Laccadive (now Lakshadweep) Islands in the 1930s is given by R. W. Burton in the Journal of the Bombay Natural History Society.
|1827||Skulls, an incomplete skeleton and a mounted specimen collected by Dussumier from Malabar coast, in the
Museum National d’Histoire Naturelle,Laboratoire d’Anatomie Comparee.
|De Silva, 1987|
|1866 [?]||“Delphinapterus molagen” described by Owen from “Madras”.||De Silva, 1987|
|1908||Several specimens purchased at Trivandrum.||Pillay, 1926|
|[?]||Skull and foetus from the mouth of Bombay Harbour in the British Museum (Natural History).||De Silva, 1987|
|[?]||Three skulls from the Malabar coast in the Bombay Natural History Society.||De Silva, 1987|
|December 1935 [?]||Ten porpoises slaughtered in a lagoon in the Laccadives.||Burton, 1940|
|12 November 1959||Seventeen porpoises landed in a large shore seine and two more together at Malpe on the South Kanara coast.
Four embryos recovered.
|12 February 1965||One female caught off Karwar.||Devaraj & Sam Bennett, 1974|
|10 February 1973||One young female specimen caught in gillnet off Calicut.||Balan, 1976|
|1976||Eight caught in gillnets off the Calicut coast.||Lal Mohan, 1985|
|20 February 1980||One caught near the mouth of the Zoari river off Vasco-da-Gama, one foetus recovered.||Hafeezullah, 1984|
|July 1983–December 1986||One male and two females landed at Cochin Fisheries Harbour.||Jayaprakash et al., 1995|
|January–March 1986||Two porpoises washed ashore at Gahirmatha, Orissa coast.||James et al., 1989|
|January–March 1987||Two porpoises washed ashore at Gahirmatha, Orissa coast.||James et al., 1989|
|8 July 1988||One 77 cm long female landed at Mandapam.||Nammalwar et al., 1994|
|11 August 1990||One 1.32 m long female landed at Pillaimadam, near Mandapam.||Nammalwar et al., 1994|
|16 November 1990||One 1.26 m female landed at Verkodu, Rameswaram.||Nammalwar et al., 1994|
|January 1992||Three specimens stranded or washed ashore near Thondi, Tamilnadu, in one week in a 5 km stretch of beach.||Ganapathy, 1992|
|29 January 1992||One immature male, 1.39 m long, collected from Porto Novo during an inshore gillnet operation.||Kumaran & Subramanian, 1993|
|25 October 1992||One 1.32 m long male landed at Agnitheertham, Rameswaram.||Nammalwar et al., 1994|
|1993 [?]||One male specimen entangled in gillnets off the Calicut coast.||Lal Mohan, 1995|
|14 September 1995||One young porpoise found washed ashore at Ullal, near Mangalore.||Muthiah, 1995|
There seem to be few records from Sri Lanka, though a number of strandings have been noted in Pakistan.
World Distribution: The Finless Porpoise is found in coastal waters of the Indo-Pacific, from Pakistan and India to China, Korea and Japan, including South-East Asia and Indonesia. In China, it shares the habitat of the highly endangered Beiji Lipotes vexillifer, a river dolphin, in the Yangtze River.
Could Be Confused With: There is a possibility of confusion with the Irrawaddy Dolphin Orcaella brevirostris, which also occurs in the same area.
|Finless Porpoise||Small||The shade is more blue than gray.||Dorsal fin absent|
|Irrawaddy Dolphin||Relatively large||The shade is more gray than blue.||Dorsal fin with rounded tip present|
Diagnostic Features: At sea, Absence of dorsal fin, rounded melon, absence of beak.
Stranded specimens: There are 13 to 22 pairs of spade-shaped teeth in each jaw. The shape of the teeth, and the tubercles on the back where the dorsal fin should be make it easy to identify a dead Finless Porpoise.