|Population||Unknown (2017 est.)|
|Conservation status||Least concern|
Dall's porpoise (Phocoenoides dalli) is a species of porpoise of the family Phocoenidae, and found primarily in coastal and deep waters of the North Pacific Ocean. It is named in honor of William Healey Dall (1845 – 1927), an American naturalist who conducted some of the earliest scientific surveys of the Alaskan coast and interior.
Although the largest living species of porpoise, Dall's porpoise is comparatively small as compared to dolphins. They are up to 7.5 feet in length, and weigh 370 to 490 lbs. Females are slightly smaller than males. They are primarily black in color, with a white belly from the genital region to in-line with the dorsal fin; the white area extends upward along the sides halfway to the top of the back. White also occurs on the upper half of the dorsal, and along the trailing edge of the tail flukes. Together, the bold coloration of black and white is rivaled only by the orca (Orcinus orca). There is very little difference between male and female, with the most obvious being males having a pronounced hump in front of the tail.
Dall's porpoise is very active, swimming in zigzags at great speed on the surface of the water or just below it, creating a spray known as a "rooster tail". They appear and disappear almost suddenly. Among the fastest of cetaceans, they can swim at 35 mph. They sometimes ride the bow wave of ships and boats, but lose interest if the boat moves rather slowly.
They are usually found in small groups of about 2-10 animals, with non-united pods of up to a thousand animals when an abundance of food is available. They feed on a large variety of fish such as herring, anchovies and mackerel, and cephalopods such as squid, diving up to 1,650 feet. They are opportunistic feeders, and will consume prey items not normally part of their diet.
- Phocoenoides dalli dalli; North Pacific Ocean, from Asia to the Bering Sea and northwestern North America.
- Phocoenoides dalli truei; Japan, Kuril and Sakhalin islands, Sea of Okhotsk.
Currently there is debate as to whether or not Dall's porpoise is a single species with two subspecies, or two distinct species (Phocoenoides dalli and Phocoenoides truei), or mere color morphs.. Genetic differences have been noted between what is called the dalli-type and the truei-type, with the truei-type noted to be exclusively in the waters near Japan, with some notable exceptions. The differences in color are minor, with truei-types having the large white side patch extending further forward on the body.
They are found near the coast and in the open sea, from Japan to the Sea of Okhotsk, northward to the Bering and Chukchi seas, east to the North American coasts of Alaska, Canada, and as far south as southern California.
The ICUN classifies Dall's porpoise as "least concern", citing the large range of the animal, along with a population guess at 1.2 million. Their only natural enemy is the orca, the only animal fast enough to catch them.
Man poses the greatest threat to the species, despite the current ICUN classification. Drift and fishing nets cause many accidental deaths; however, a moratorium on whaling enacted during the mid-1980s caused an increase in the hunting and harvesting of porpoises in Japan, with 40,000 killed in 1988 alone. Currently, an annual quota of 18,000 animals per year is in operation.