WWF Pakistan Special Bulletin # 01: Impact on Marine Mammals
Friday, August 15th, 2003: 17:32:54
Whales and dolphins are all members of the same group of marine and aquatic mammals that is known as the Cetacea. There are about 80 living species of Cetaceans on earth and about 15 of these are known to either live in Pakistan’s coastal waters or visit Pakistan’s coastline from time to time.
Four great whale species, the Fin Whale, Blue Whale, Bryde’s Whale, and Humpback Whale have been sighted in the vicinity of Karachi and the Indus Delta. They are not, however, likely to visit the area during the late summer season.
The situation with dolphins and porpoises, the smaller species, is quite different and the key information is summarised in the following table:
List of endangered dolphins and porpoises that occur near Karachi# / Names / Status / Level of threat from the Karachi oil spill
Common / Scientific
1 / Finless Black Porpoise / Neophocaena phocaenoides / Endangered / Quite serious – the species frequents the edge of mangrove swamps from late August to April.
2 / Long-beaked Dolphin / Delphinus tropicalis / Endangered / Slight – the species tends to stay offshore and only occasionally comes to the shore-line
3 / Rough-toothed Dolphin / Steno bredanensis / Endangered / Slight – the species tends to stay offshore, frequenting the continental shelf.
4 / Indo-Pacific Humpback Dolphin / Sousa plumbea / Endangered / Very serious – the species frequents the inshore waters bays of the coastline where it feeds in shallow water
5 / Bottle-nosed Dolphin / Tursiops truncatus / Endangered / As for species #4
There are records of at least three other dolphins or dolphin-like species that have been recorded on the Pakistan coast but all are regarded to be infrequent visitors.
Indus River Dolphin: Pakistan’s endangered Indus River Dolphin is not threatened by the oil spill as this species of dolphin is confined entirely to the freshwater portion of the Indus River up stream of Kotri Barrage near Hyderabad.
Whale and dolphin strandings: In March, 2003, a dead adult male Humpback Whale washed ashore on Clifton Beach, Karachi. Although samples were taken for analysis, the cause of the whale’s death has not, so far, been determined. Over the years, individual whales and dolphins and in some cases small groups of dolphins have washed up dead on Pakistan’s beaches. Most recently a group of about a dozen Humpback dolphins died of some undetermined cause in the waters off Karachi in 2001.
How can such an oil spill affect Dolphins? Leakage of petroleum (oil) onto the surface of a large body of water like the sea usually initially results in the formation of a slick or film of oil on the surface. This slick may vary in thickness but, if it is continuous over a relatively large area, it is likely to have devastating effects on vulnerable forms of sea life.
The slick may prevent sufficient sunlight entering the water which will retard the growth and even kill photosynthetic plants such as algae that form the base of the marine food chain. The slick may also cut off contact between the water and the atmosphere resulting in a low level of dissolved oxygen in the surface waters. This will kill sensitive fish species and other forms of marine life. Fish that come into direct contact with oil are unable to breathe as their gills become coated.
Dolphins, like other marine mammals and reptiles, breathe air. To do so, they must periodically rise to the surface. In doing so, they become coated with oil that clings to their bodies, covers their eyes, mouths and blowholes (nostrils). This coating of oil may be extremely irritating and is likely to severely disrupt the animal’s behaviour causing it to become disorientated and incapable of communicating with its companions. Oil that is inadvertently inhaled severely damages lung tissues and interferes with respiration. If the dolphins feed on fish killed or incapacitated by direct contact with the oil, they may be poisoned.
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For further information, please contact:
Richard Garstang, Conservation Advisor, WWF – Pakistan. Tel: +92 042 5862360 Email:
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WWF-Pakistan special bulletin on the Karachi oil spill crisis – August, 2003 Page 1 of 1