Dall'S Porpoise

Dall's porpoises can be easily distinguished from other porpoises and cetacean species within their range. They have a wide, robust body, a comparatively tiny head, and no distinguished beak. Their flippers are positioned at the front of the body and a triangular dorsal fin sits mid-body. Patterns of coloration are highly variable, but Dall's porpoises are mostly black, have white to grey patches on the flank and belly, and frosting on the dorsal fin and trailing edge of the fluke.

Dall's porpoises are limited to the North Pacific: in the east from California to the Bering Sea and Okhotsk Sea, and in the west down to the Sea of Japan. They have been sighted as far south as Scammon's Lagoon in Baja California when water temperature was unseasonably cold.

Dall's porpoises generally prefer cold waters less than 18 °C (64 °F). Although mostly an offshore species, they do occur in deeper coastal waters, near submarine canyons or in fjords.

Dall's porpoises are opportunistic, hunting a variety of surface and mid-water species. Common prey are mesopelagic fish, such as myctophids, and gonatid squid. Stomach content analyses have also found cases of crustacean consumption, including krill and shrimp, but this is abnormal and likely not an important part of their diet. A previous study revealed that tagged Dall's porpoises spent most of their time within 10 m of the surface, but have been recorded diving to depths of up to 94 m.

Abundance throughout their range and is estimated to be over one million, but current population trends are unknown.

Surveys along the coasts of California, Oregon, and Washington between 2008 and 2014 estimated a population abundance of 25,800. Alaska's population is estimated to be 83,400. Abundance in coastal British Columbia is nearly 5,000 individuals.

Populations in the western North Pacific are divided by both subspecies and migratory patterns. Abundance of the offshore dalli type is about 162,000. It is estimated that there are about 173,000 dalli type that travel between Japan and the southern Okhotsk Sea. The dalli type that migrates to the Okhotsk Sea in the summer is estimated at 111,000. The population of truei-type porpoises migrating between Japan and the central Okhotsk Sea number about 178,000.