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Atlantic White-Sided Dolphin (Lagenorhynchus acutus)

Status | Species Description | Habitat | Distribution | Population Trends | Threats | Conservation Efforts | Regulatory Overview | Taxonomy | Key Documents | More Info


MMPA - Atlantic white-sided dolphins, like all marine mammals, are protected under the MMPA
CITES Appendix II - throughout its range

Species Description

400-500 pounds (180-225 kg)
up to 9 feet (3 m)
black, with white belly and lower beak
about 25 years
fish (like mackerel, herring and hake), squid, and shrimp
highly social and playful animals, commonly seen lobtailing and breaching

Atlantic white-sided dolphins have a robust body, short beak, and a distinct color pattern, including a bi-colored beak. Their back, fluke, flippers, dorsal fin, and top beak are black, while their belly and lower beak are white. Their sides are gray, with a white patch that begins below the dorsal fin and is flanked by a yellowish-tan streak that extends to the fluke, or tail. Atlantic white-sided dolphins can sometimes be confused with the white-beaked dolphin, which shares a similar distribution pattern.

Males reach lengths of about 9 feet (3 m) and females grow to about 8 feet (2.5 m). The average adult Atlantic white-sided dolphin weighs about 400-500 pounds (180-225 kg). They have a lifespan of approximately 25 years.

Atlantic white-sided dolphins are highly social and playful animals. They have been seen traveling in small groups of a few individuals and in large aggregations of up to 500 animals. They are commonly observed engaging in acrobatic activities, such as lobtailing and breaching.

Atlantic white-sided dolphins are capable of holding their breath for nearly 5 minutes. They dive to feed on prey, such as fish (e.g., mackerel, herring and hake), as well as squid and shrimp. They are often seen in association with long-finned pilot whales, humpback whales, and fin whales while feeding.

Females reach sexual maturity and begin breeding between 6 to 12 years of age, when they reach lengths of about 7 feet (2.1 m). The gestation period is 11 months and lactation occurs for 12-18 months. Females typically give birth to a single calf about every other year. Breeding season is from May to August, though most calves are born in June and July.


Atlantic white-sided dolphins are found only in temperate waters of the North Atlantic Ocean. They inhabit the oceanic waters of the continental shelf and slope.


Atlantic white-sided dolphins are found in the western North Atlantic from 35°-80° N, from North Carolina to Greenland. This species exhibits seasonal movements, moving closer inshore and north in the summers and offshore and south in the winters.

Population Trends

The most recent stock assessment reports with population estimates are available on our website.


Conservation Efforts

The Atlantic Trawl Gear Take Reduction Team and Plan addresses the incidental bycatch of white-sided dolphins--as well as long-finned pilot whales (Globicephala melas), short-finned pilot whales (Globicephala macrorhynchus), and common dolphins (Delphinus delphis)--in bottom and mid-water trawl fisheries in the Northeast and Mid-Atlantic.

Regulatory Overview

This species is protected under the Marine Mammal Protection Act of 1972, as amended.


Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus
Species: acutus

Key Documents

(All documents are in PDF format.)
Title Federal Register Date
Atlantic Trawl Gear Take Reduction Plan 71 FR 54273 09/11/2006
Stock Assessment Reports n/a various

More Information

Updated: January 15, 2015