Pacific White-sided Dolphin

The Pacific White-sided Dolphin (Lagenorynchus obliquidens) is a very active dolphin found in the cool to temperate waters of the North Pacific Ocean.


Theodore Gill named the Pacific White-sided Dolphin in 1865 who examined three skulls found washed up in California. It is the only species of the genus Lagenorhynchus to be found in the North Pacific.

The Pacific White-sided Dolphin is extremely similar in structure to the Dusky Dolphin, which is found in the southern part of the Pacific. Some researchers have suggested that they might form a single species. Recent genetic work by Cipriano rejects this hypothesis and suggests the two species diverged about two million years ago.

Physical description

The Pacific White-sided Dolphin has three tones of color. The chin, throat and belly are creamy white. The beak, flippers back and dorsal fin are a dark gray. There is light gray patch on the sides and a further light gray stripe running from above the eye to below the dorsal fin where it thickens along the tail stock. A dark gray ring surrounds the eyes.

This Dolphin species is of average size for an oceanic dolphin and can weigh up to 330 pounds (150kg) in females and 440 pounds (200kg) in males and growing up to 8 ft (2.5 meters)in males and 9ft (2.3 meters) in females in length. Pacific White-sided Dolphins tend to be rather larger than Dusk. Females reach maturity at 7 years. The gestation period is one year. Individuals can live for up to forty years or more.

The Pacific White-sided Dolphin is extremely active and mixes with many of the other cetacean species to be found in the north Pacific. It also readily approaches boats and bow-rides. Large groups are common – on average 90 individuals per group but super groups of more than 3,000 have been recorded. Prey is mainly lantern fish, hake, anchovies, squid, herring, salmon and cod.

Population and distribution

The range of the Pacific White-sided Dolphin runs right in a great arc across the cool to temperate waters of the north Pacific. Sightings go no further south than the South China Sea on the western side and the Baja California peninsula on the eastern. Populations may also be found in the Sea of Japan and the Sea of Okhotsk. In the northern part of the range, some individuals may be found in the Bering Sea. The dolphins appear to follow some sort of migratory pattern ““ on the eastern side they are most abundant off the California shore in winter, but further north (Oregon, Washington) in summer. Their preference for offshore deep waters appears to be year-round.

The total population may be as many as 1 million. However such is the tendency of Pacific White-sided Dolphins to approach boats from some distance away, it is harder than usual to obtain precise estimates via sampling.