Pacific White-sided Dolphin
Encyclopedia
The Pacific White-sided Dolphin (Lagenorhynchus obliquidens) is a very active dolphin
found in the cool to temperate waters of the North Pacific Ocean
.
, which is found in the southern Pacific. Genetic analysis by Frank Cipriano suggests the two species diverged about two million years ago.
Though both are traditionally placed in the genus Lagenorhynchus, molecular
analyses indicate that they are closer to dolphins of the genus Cephalorhynchus
. The new genus Sagmatias
has been proposed for these species.
The Pacific White-sided Dolphin has three colors. The chin, throat and belly are creamy white. The beak
, flippers, back, and dorsal fin
are a dark gray. There are light gray patches 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.
The species is an average-sized oceanic dolphin. Females weigh up to 150 kilograms (330.7 lb) and males 200 kilograms (440.9 lb) with males reaching 2.5 metres (8.2 ft) and females 2.3 metres (7.5 ft) in length. Pacific White-sided Dolphins tend to be larger than Dusky Dolphins. Females reach maturity at 7 years. The gestation period is one year. Individuals live 40 years or more.
The Pacific White-sided Dolphin is extremely active and mixes with many of the other north Pacific cetacea
n species. It readily approaches boats and bow-rides. Large groups are common; averaging 90 individuals, with supergroups of more than 300. Prey is mainly hake
, anchovies
, squid
, herring
, salmon
and cod
.
They have an average of 60 teeth.
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 off-shore deep waters appears to be year-round.
The total population may be as many as 1 million. However, the tendency of Pacific White-sided Dolphins to approach boats complicates precise estimates via sampling.
banned certain types of fishing nets in 1993, many Pacific White-sided Dolphins were killed in drift net
s. One researcher estimated somewhere 50,000–89,000 individuals were killed in the twelve years to 1990. Some animals are still killed each year by Japanese hunting drives.
Pacific White-sided Dolphins adapt well to captivity. Almost 50 reside in dolphinariums in North America and Japan.
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
found in the cool to temperate waters of the North Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
Taxonomy
The Pacific White-sided Dolphin was named by Smithsonian mammalogist Theodore Nicholas Gill in 1865. The Pacific White-sided Dolphin is morphologically similar to the Dusky DolphinDusky Dolphin
The dusky dolphin is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus is that they are distinct species...
, which is found in the southern Pacific. Genetic analysis by Frank Cipriano suggests the two species diverged about two million years ago.
Though both are traditionally placed in the genus Lagenorhynchus, molecular
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
analyses indicate that they are closer to dolphins of the genus Cephalorhynchus
Cephalorhynchus
Cephalorhynchus is a genus in the dolphin family Delphinidae. It consists of four species:*Commerson's Dolphin, Cephalorhyncus commersonii*Chilean Dolphin, Cephalorhyncus eutropia*Heaviside's Dolphin, Cephalorhyncus heavisidii...
. The new genus Sagmatias
Sagmatias
Sagmatias is a genus that has been proposed for certain dolphin species that are currently placed in the genus Lagenorhynchus. Mitochondrial DNA studies have indicated that certain dolphin species within Lagenorhynchus are actually more closely related to dolphins within the genus Cephalorhynchus...
has been proposed for these species.
Physical description
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
, flippers, back, and dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
are a dark gray. There are light gray patches on the sides and a further light gray stripe running from above the eye to below the dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
where it thickens along the tail stock. A dark gray ring surrounds the eyes.
The species is an average-sized oceanic dolphin. Females weigh up to 150 kilograms (330.7 lb) and males 200 kilograms (440.9 lb) with males reaching 2.5 metres (8.2 ft) and females 2.3 metres (7.5 ft) in length. Pacific White-sided Dolphins tend to be larger than Dusky Dolphins. Females reach maturity at 7 years. The gestation period is one year. Individuals live 40 years or more.
The Pacific White-sided Dolphin is extremely active and mixes with many of the other north Pacific cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
n species. It readily approaches boats and bow-rides. Large groups are common; averaging 90 individuals, with supergroups of more than 300. Prey is mainly hake
Hake
The term hake refers to fish in either of:* family Phycidae of the northern oceans* family Merlucciidae of the southern oceans-Hake fish:...
, anchovies
Anchovy
Anchovies are a family of small, common salt-water forage fish. There are 144 species in 17 genera, found in the Atlantic, Indian, and Pacific Oceans. Anchovies are usually classified as an oily fish.-Description:...
, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
, salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
and cod
Cod
Cod is the common name for genus Gadus, belonging to the family Gadidae, and is also used in the common name for various other fishes. Cod is a popular food with a mild flavor, low fat content and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of...
.
They have an average of 60 teeth.
Range and habitat
The range of the Pacific White-sided Dolphin arcs across the cool to temperate waters of the north Pacific. Sightings go no further south than the South China SeaSouth China Sea
The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...
on the western side and the Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
on the eastern. Populations may also be found in the Sea of Japan
Sea of Japan
The Sea of Japan is a marginal sea of the western Pacific Ocean, between the Asian mainland, the Japanese archipelago and Sakhalin. It is bordered by Japan, North Korea, Russia and South Korea. Like the Mediterranean Sea, it has almost no tides due to its nearly complete enclosure from the Pacific...
and the Sea of Okhotsk
Sea of Okhotsk
The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...
. In the northern part of the range, some individuals may be found in the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
. The dolphins appear to follow some sort of migratory pattern—on the eastern side they are most abundant off the California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
shore in winter, but further north (Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, Washington) in summer. Their preference for off-shore deep waters appears to be year-round.
The total population may be as many as 1 million. However, the tendency of Pacific White-sided Dolphins to approach boats complicates precise estimates via sampling.
Protection
Until the United NationsUnited Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
banned certain types of fishing nets in 1993, many Pacific White-sided Dolphins were killed in drift net
Drift net
Drift netting is a fishing technique where nets, called drift nets, are allowed to float freely at the surface of a sea or lake. Usually a drift net is a gill net with floats attached to a rope along the top of the net, and weights attached to another rope along the foot of the net to keep the net...
s. One researcher estimated somewhere 50,000–89,000 individuals were killed in the twelve years to 1990. Some animals are still killed each year by Japanese hunting drives.
In popular culture
- Although overshadowed in popularity by Bottlenose DolphinBottlenose DolphinBottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s, Pacific White-sided Dolphins are also a part of some marine theme park shows. - Venus Among the Fishes is a book by Elizabeth HallElizabeth Hall-People:*Elizabeth Barnard, née Elizabeth Hall, William Shakespeare's granddaughter*Elizabeth Hall , British cross country runner and steeplechaser-Place:...
, that has a female Pacific White-sided dolphin as its protagonist.
Captivity