Lagenorhynchus obliquidens

Before the United Nations established a moratorium on the use of high seas drift nets in 1993, Pacific white-sided dolphins were frequently caught in the nets of Japanese and Korean squid fisheries. Today the species is better protected, and the total North Pacific population is estimated to approach one million. They are often seen swimming with seals and sea lions, and sometimes with other cetaceans, especially the northern right whale dolphin, perhaps because they are all pursuing the same prey. Females are mature and ready to reproduce when they are about 10 or 11 years old, and gestation lasts about 10 months. A newborn calf is about a meter long.

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Mammal Species of the World

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Pacific white-sided dolphins inhabit temperate waters of the North Pacific and some adjacent seas (Sea of Japan, southern Okhotsk Sea, the southern Bering Sea and southern Gulf of California) (Brownell et al. 1999; Van Waerebeek and Würsig 2002). Their range includes continental slope waters of the Western North Pacific as far south as southern China, shelf and slope waters of the eastern North Pacific from the Gulf of Alaska southward to Baja California, Mexico, and deep offshore waters of the North Pacific between about 35˚N and 47˚N latitude (Hobbs and Jones 1993).

Pacific white-sided dolphins have a primarily temperate distribution, remaining north of the tropics and south of the colder waters caused by arctic currents. Their range is from the Aleutian Islands through the Gulf of Alaska to the tip of Baja California in the eastern Pacific; and from Japan to the Kuril Islnads in the western Pacific.

Biogeographic Regions: pacific ocean (Native )

North Pacific

occurs (regularly, as a native taxon) in multiple nations

Global Range: Kamchatka Peninsula, Amchitka Island, and Kodiak Island south into Sea of Japan and along entire Pacific coast of Japan, and south to tip of Baja California in the eastern Pacific.

Pacific white-sided dolphins have torpedo-shaped bodies which help them move quickly through water. Body length of Pacific white-sided dolphins ranges from 150 to 310 cm. Their coloration is one of their most distinguishing features, they are black or dark gray on the dorsal surface with a white underside, and have bicolored fins and flippers. This coloration is believed to act as a form of camouflage in their aquatic environment.

Range mass: 82 to 124 kg.

Sexual Dimorphism: Males are slightly larger than females.

Length:
Range: "1.7-2.5 m "

Weight:
Range: 75-200 kg

Length: 2700 cm

Weight: 150000 grams

Habitat and Ecology

Systems

• Marine

They are usually seen in deep waters up to 160 km (100 miles ) offshore. There seem to be local migrations inshore in the winter months.

Aquatic Biomes: coastal

offshore waters, sometimes near shore

Depth range based on 1350 specimens in 1 taxon.
Water temperature and chemistry ranges based on 785 samples.

Environmental ranges
  Depth range (m): 0 - 500.83
  Temperature range (°C): 4.730 - 21.311
  Nitrate (umol/L): 0.082 - 40.485
  Salinity (PPS): 30.381 - 34.257
  Oxygen (ml/l): 0.435 - 7.358
  Phosphate (umol/l): 0.330 - 3.118
  Silicate (umol/l): 1.436 - 78.143

Graphical representation

Depth range (m): 0 - 500.83

Temperature range (°C): 4.730 - 21.311

Nitrate (umol/L): 0.082 - 40.485

Salinity (PPS): 30.381 - 34.257

Oxygen (ml/l): 0.435 - 7.358

Phosphate (umol/l): 0.330 - 3.118

Silicate (umol/l): 1.436 - 78.143
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Mostly between seaward edge of continental slope and 100-fathom contour; sometimes closer to shore if there is deep water nearby (Leatherwood and Reeves 1983). In Canada, depth of water at sighting locations ranged from 10 to 2000 fathoms, with mean, median, and modal depths of 617, 400, and 100 fathoms, respectively (Stacey and Baird 1991).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Seasonal movements not well understood in most areas. Off southern and central California and northwestern Baja California, apparently resident pods are augmented during fall through spring by influxes of animals possibly from north and offshore (Leatherwood and Reeves 1983).

Pacific white-sided dolphins eat fish that live in large schools, such as anchovies, herring, smelt, capelin, and mackerel. They feed in groups of 10-20 dolphins, each adult eating about 9 kilograms (20 lbs ) of food each day.

Animal Foods: fish

Primary Diet: carnivore (Piscivore )

Comments: Eats various fishes (anchovies, hake, sauries) and squid. Apparently feeds primarily at night. Has been seen at dawn and dusk feeding with gulls on small surfacing balls of unidentified bait fishes. (Leatherwood and Reeves 1983).

10,000 to >1,000,000 individuals

Comments: Two 1970s estimates: 30,000-50,000 in Japanese waters; about 24,000 in 1.5 million sq km off California and Baja California (see IUCN 1991).

Gregarious. Forms herds of a thousand or more, though usually groups are of several hundred or less; herds generally are of all age classes and both sexes.

Comments: Feeding may occur mainly at night.

Average lifespan
Status: captivity: 20.0 years.

Maximum longevity: 46 years (captivity) Observations: It has been estimated that these animals live up to 46 years (Don Wilson and Sue Ruff 1999). One wild born specimen was about 36-37 years old when it died in captivity (Richard Weigl 2005).

Pods are made up of one dominant male and a number of other males and females. The dominant male mates with reproductively available females.

Mating System: polygynous

Female Pacific white-sided dolphins reach sexual maturity around 5-6 years of age, males are sexually mature at 8-10 years. Generally breeding occurs in the summer or fall, and gestation lasts approximately 11-12 months. Females give brith to a single calf, which is almost 3 feet long and can weigh up to 14 pounds.

Breeding season: Generally breeding occurs in the summer or fall.

Average number of offspring: 1.

Range gestation period: 11 to 12 months.

Range age at sexual or reproductive maturity (female): 5 to 6 years.

Range age at sexual or reproductive maturity (male): 8 to 10 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 14000 g.

Average number of offspring: 1.

Calving season has been reported to be summer, but in recent studies calves have been found primarily in early fall (Leatherwood and Reeves 1983).

High seas drift net samples in Central North Pacific (Ferrero and Walker 1996): a calving period preceded sampling during late winter and spring; estimated gestation period 11-12 months; males sexually mature in 10-11 years, females in 8-11 years.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 3 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: NU - Unrankable

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 1996
  Lower Risk/least concern
• 1994
  Insufficiently Known
  (Groombridge 1994)

Pacific white-sided dolphins are not considered to be endangered. A recent estimate of the population of these mammals in the central North Pacific ranged between a minimum of about 500,000, to a maximum of 930,000. Therefore there is not any immediate danger for the extiction of these animals. They are hunted by Japanese coastal fishermen in the East China and Japan seas and taken accidentally in the North Pacific purse-seine fishery.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Comments: Taken directly and incidently in small numbers in various fisheries through the range, but apparently not seriously threatened (Stacey and Baird 1991).

Conservation Actions

Comments: Taken in small numbers for human consumption in Japan (IUCN 1991). Sometimes displayed in marine aquaria.

Least Concern (LC)