Dall's porpoise
| Dall's porpoise | |
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| Size compared to an average human | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Phocoenidae |
| Genus: |
Phocoenoides Andrews, 1911 |
| Species: | P. dalli |
| Binomial name | |
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Phocoenoides dalli (True, 1885) |
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| Dall's porpoise range | |
Dall's porpoise (Phocoenoides dalli) is a species of porpoise found only in the North Pacific. It came to worldwide attention in the 1970s when it was disclosed for the first time to the public that salmon fishing trawls were killing thousands of Dall's porpoises and other cetaceans each year by accidentally capturing them in their nets. Dall's porpoise is the only member of the genus Phocoenoides. It was named after American naturalist W. H. Dall.
The unique body shape of Dall's porpoise makes it easily distinguishable from other cetacean species. The animal has a very thick body and a small head. The colouration is rather like that of a killer whale; the main body of the porpoise is very dark grey to black, with very demarcated white patches on the flank and belly. The dorsal fin is set just back from the middle of the back and sits up erect. The upper part of the dorsal fin has a white to light grey "frosting".
The has a similar frosting. The adult fluke curves back towards the body of the animal, which is another distinguishing feature. It is larger than other porpoises, growing up to 2.3 m (7.5 ft) in length and weighing between 130 and 220 kg (290 and 490 lb). There is also sexual dimorphism in the species, with males being larger, having a deeper caudal peduncle and a pronounced hump behind the anus. Young Dall's have a greyish tint and dark-colored flukes.
Dall’s porpoise ranges through much of the North Pacific and nearby seas, such as the Bering and Okhotsk Seas and the Sea of Japan. The southernmost part of its range is southern Japan in the west and southern California in the east, while it is northernmost range is the central Bering Sea. They do enter Scammon's Lagoon in Baja California, though, when the waters are unseasonably cold. They also travel up to the Chukchi Sea, though very rarely.
Dall’s porpoise prefers cold waters more than 180 metres (590 ft) deep. It is found over the continental shelf adjacent to the slopes and oceanic waters. While it mostly lives in offshore waters, it does occur in deep coastal waters on off North America. There, it typically stays close to deep-water canyons.
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Wikipedia