Population and Distribution
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.
Two consistent and well-defined colour morphs, the dalli-type and the truei-type, have been identified. The dalli-type is present throughout the porpoise’s range, while the truei-type lives mostly on the western Pacific and is rare in the east. There is some question as to whether the morphs are merely colour patterns (the truei-type having a more extensive belly patch) or whether they are separate subspecies.. They are believed to number around 104,000 off Japan, 554,000 in the Okhotsk Sea, 83,000 off Alaska and 100,000 off the continental US.
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