Dalls porpoise

Phocoenoides dalli

Dall's porpoise is a species of porpoise endemic to the North Pacific. It is the largest of porpoises and the only member of the genus ''Phocoenoides''. The species is named after American naturalist W. H. Dall.
Dall's porpoise From a ferry boat in Alaska.  Very very difficult to photograph, very fast and not on the surface for any period other than the porpoising swim.  They are the fastest small cetacean up to 55kph. Alaska,Dalls porpoise,Phocoenoides dalli

Appearance

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.

They are the largest porpoise species, growing up to 7.5 ft in length and weighing between 370 and 490 lbs. Sexual dimorphism is apparent in body size and shape, with mature males being larger, developing a deeper caudal peduncle, and having a dorsal fin that’s significantly angled forward in comparison to a female’s. Dall’s porpoise calves have a greyish coloration with no frosting on flippers and flukes. Calves measure about 100 cm at birth. Growth rates are similar at first, but at about 2 years old males begin to grow faster than females. Externally, maturity is measured by length which is usually attained at 3 – 5 years old. Sizes vary between populations, but on average females reach a maximum size of 210 cm and males grow to about 220 cm, except in the southern Okhotsk Sea where males can grow as long as 239 cm.

Two colormorphs have been identified: the ''dalli''-type and ''truei''-type. The ''truei''-type, found only in the western Pacific, has a white belly patch that extends farther forward across the body than that of the ''dalli''-type.
Dall's Porpoise, porpoising Found another Dall's porpoise, amazing speed, we were en route to Seward - Magical place! Alaska,Dalls porpoise,Phocoenoides dalli,Resurrection Bay,Seward

Distribution

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 64 °F . Although mostly an offshore species, they do occur in deeper coastal waters, near submarine canyons or in fjords.Abundance throughout their range and is estimated to be over 1 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.

Status

Abundance throughout their range and is estimated to be over 1 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.Dall’s porpoise is listed as Least Concern on the IUCN Red List. Levels of both bycatch and commercial hunting are likely underestimates because they account only for reported data; however, there is no evidence for a range-wide decline of the species.

The species is also listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals , and, like all other marine mammal species, is protected in the United States under the Marine Mammal Protection Act .

Behavior

Dall's porpoises live in small, fluid groups of 2 – 10 individuals, but aggregations of hundreds have been reported. They have a polygynous mating system in which males compete for females. During the mating season, a male will select a fertile female and guard her to ensure paternity. While guarding, males may sacrifice opportunities to forage on deep dives. Births usually take place in the summer after a gestation period of 11 – 12 months. Females generally give birth every 3 years, depending on their condition. Life expectancy is about 15 – 20 years, but a lot about their mortality is unknown.

Dall’s porpoises are prey to transient killer whales. They have, however, been observed in association with resident killer whales, engaging in apparent play behaviors with their calves, and swimming with them. One recognizable Dall’s porpoise was observed travelling with the AB pod of resident orca from May through October 1984.

Habitat

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 64 °F . Although mostly an offshore species, they do occur in deeper coastal waters, near submarine canyons or in fjords.

Food

The Dall's porpoise is still harvested for meat in Japan. The number of individuals taken each year increased following the 1980s moratorium on whaling of larger cetacean species. In 1988, more than 45,000 Dall’s porpoises were harpooned. In 1990, after international attention was drawn to the issue, the Japanese government introduced a reduction on take. A quota of over 17,000 a year is in effect today making it the largest direct hunt of any cetacean species in the world. The hunt of Dall’s porpoises has been criticized by scientific committees which question the sustainability of large quotas on regional populations. Assessments are outdated for these targeted populations, and given the level of annual reported take, there may be regional declines in abundance.

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Status: Least concern
EX EW CR EN VU NT LC
Taxonomy
KingdomAnimalia
DivisionChordata
ClassMammalia
OrderArtiodactyla
FamilyPhocoenidae
GenusPhocoenoides
SpeciesP. dalli