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Lifespan, longevity, and ageing

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Maximum longevity: 20.4 years (captivity) Observations: These animals rarely live more than 13 years in the wild (Ronald Nowak 1999). One captive specimen was still alive at 20.4 years of age (Richard Weigl 2005).
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Life Expectancy

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Average lifespan
Status: wild:
13.0 years.

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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George Hammond, Animal Diversity Web
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Morphology

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Phocoena phocoena, also known as the "Common" or "Harbor" Porpoise, is a small cetacean that is 1.5 to 2 meters long and weighs from 45 - 65 kilograms. The female of the species is usually slightly larger than the male. The color of the animal varies from individual to individual, but the most common coloration pattern is a dark dorsal surface that shifts to a lighter colored hue ventrally. Although the dark color is usually black or deep gray, albinos have been reported in which the dark segments are completely or partially white. The flippers, dorsal fin, and tail are all dark in color, and there is a black stripe that runs from the edge of the mouth or eye to the flipper on either side. There is no noticeable forehead or beak on this species, and the snout is short, giving the head a somewhat cone-like shape. P. phocoena has two pectoral flippers, a single dorsal fin, and a tail with two partially separated flukes. All of these appendages are short and not very sharp, with the dorsal fin being triangular shaped and usually around 15 - 20 cm tall. There is a noticeable keel located near the all dark tail flukes, with the tail itself spanning anywhere from 30-65 cm. Inside the slightly upturned mouth there are rows of 16-28 spade-shaped teeth. There is no variance in the shape or type of teeth in P. phocoena.

Range mass: 45 to 60 kg.

Range length: 1.5 to 2 m.

Sexual Dimorphism: female larger

Other Physical Features: endothermic ; bilateral symmetry

Average basal metabolic rate: 107.675 W.

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Habitat

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Found in both salt and fresh water areas, Phocoena phocoena require a shallow coastal body of water. In the Western Atlantic, they also move far out to sea near the end of summer and reappear in spring. Other regional populations move south or farther away from shore to avoid ice buildups.

Habitat Regions: temperate ; polar ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; rivers and streams; coastal ; brackish water

Other Habitat Features: estuarine

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Distribution

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Found in coastal regions of the North Atlantic, Arctic, and North Pacific Oceans; also the Mediterranean and Black Sea regions. They are found in bays, estuaries, river mouths, and sometimes ascend further up rivers.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); arctic ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Other Geographic Terms: holarctic

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Trophic Strategy

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Diet consists mainly of smooth, non-spiny fish, and cephalopods. Herring, pollack, hake, sardines, and cod are commonly eaten. Other sea creatures such as squid and shrimp are also consumed. P. phocoena produces click-like sounds similar to those used by other cetaceans as a means of echolocation in order to locate food.(Johnston(1999), Nowak(1999))

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Benefits

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Taken heavily in various areas, the meat is used for human and animal consumption, and its oil is used in lamps and as a lubricant.

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Conservation Status

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Although fishing of P. phocoena is now illegal in most areas, the species is still in danger. Deliberate and accidental deaths still occur because modern fishing nets are almost undetectable to porpoises. Since these nets are commonly used in nearshore areas, in the natural range of P. phocoena, they probably kill large numbers of porpoises. Various measures are being taken in the United States and other nations in an attempt to limit deaths of this kind. In addition to deaths related to fishing, porpoises also suffer from chemical and noise pollution. (Dollinger(1988), Johnston(1999), McWilliam(1999), Nowak(1999))

CITES: appendix ii

IUCN Red List of Threatened Species: critically endangered

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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George Hammond, Animal Diversity Web
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Behavior

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Perception Channels: tactile ; chemical

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Untitled

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One interesting danger that the Harbor Porpoise may be facing is completely natural. As one group of researchers noticed, a number of porpoise carcasses taken in Scotland all had similar puncture and bruise wounds, with most of them dying as a result of internal injury. In addition to these injuries some of the specimens also had teeth gouges in their flesh. After analyzing these bite patterns, the researchers determined that the animal responsible for inflicting these wounds was Tursiops truncatus, the Bottlenosed Dolphin. At least in this area of Scotland it seems that where the two species' ranges overlap, dolphins are attacking and in some cases killing porpoises. It is not known for sure exactly what is prompting this kind of behavior.

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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George Hammond, Animal Diversity Web
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Reproduction

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It is not clearly known how extensive the mating season is in P. phocoena, but it seems that mating mainly occurs from June to September with births occurring from May to August. It is commonly noted that gestation lasts 11 months with nursing following for another 7 or 8 months. A female will give birth to one calf per year, with the birth size of the calf being 6-8kg and 70-100cm long. Sexual maturity is reached by the fifth year, if not before, and the life span of P. phocoena is believed to be anywhere from 6 to 20 years. (Johnston(1999), Nowak(1999))

Breeding interval: A female will give birth to one calf per year

Breeding season: Mating mainly occurs from June to September

Average number of offspring: 1.

Average gestation period: 11 months.

Range weaning age: 7 to 8 months.

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

Range age at sexual or reproductive maturity (male): 5 (high) years.

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

Average birth mass: 7000 g.

Average gestation period: 320 days.

Average number of offspring: 1.

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Masi, A. 2000. "Phocoena phocoena" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoena_phocoena.html
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Andrew Masi, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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George Hammond, Animal Diversity Web
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Biology

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A social species, the harbour porpoise travels in groups numbering between two to five individuals (2), but larger groups may form during migration (4). It feeds on a variety of fish, including herring, mackerel and anchovy (2), a variety of invertebrates are also taken (4). It is known that echolocation is used in the detection and capture of prey, but this is not yet fully understood. Sight and passive listening (for the sounds made by prey) are also important during hunting (7). Mating occurs in summer, and gestation (pregnancy) takes 11 months (4). The calf is suckled for up to eight months and sexual maturity is reached at about four years of age (4). The harbour porpoise has possibly the shortest life-span of any cetacean; they rarely live for more than 12 years (2).
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Conservation

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A UK Biodiversity Action Plan priority species, the harbour porpoise is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders, 1985; it is illegal to intentionally kill, injure, or harass any cetacean (whale or dolphin) species in UK waters (3). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by seven European countries, including the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (7). Increased awareness of this species may help to secure its future (2).
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Description

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The harbour porpoise is the most commonly seen porpoise (2), and is the most widely distributed of all cetaceans (whales and dolphins) in northern Europe (4). It is easily recognised as it has a low triangular dorsal fin and lacks a beak (2). It is small in comparison to other porpoises, has a plump body with a dark grey to bluish coloured back, a pale belly and a rounded head (5). At birth, young harbour porpoises are dull in colour and typically have 'birth lines', which look like folds in the skin, and persist for the first few hours after birth (5).
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Habitat

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Favours shallow, cold coastal waters (4). Most sightings have been made within ten kilometres of the land. It frequents relatively shallow bays, estuaries, and tidal channels under about 200 kilometres in depth, and will swim a considerable distance up river (6).
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Range

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Found in sub-Arctic and cool temperate waters of the North Atlantic and North Pacific (5), the harbour porpoise is typically a species of coastal areas, although it also occurs over most of the European continental shelf (4). In the UK, seasonal concentrations occur between July and October off western and south-western Ireland, west Wales, the west of Scotland, around Shetland and Orkney as well as around north-east Scotland (4). This species used to occur in the south coast of England and southern parts of the North Sea, but it is now rare in these waters (4).
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Status

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Classified as Least Concern (LC) under the IUCN Red List (1). Listed on Annexes II and IV of the EC Habitats Directive, Appendix II of the Bern Convention, and North, Baltic and Black Sea and western North Atlantic populations are listed under Appendix II of the Bonn Convention (the Convention on Migratory Species). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited, the species is also listed on Appendix II of CITES. Covered by the terms of the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS). In the UK all cetaceans are fully protected under Schedule 5 the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985 (3).
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Threats

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Since the 1940s, there is evidence of a decline in the numbers of this species in UK waters (3). The main threats are thought to include entanglement in fishing nets, chemical and noise pollution, hunting, boat traffic, and lack of food (5).
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Brief Summary

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During the Middle Ages, porpoises were called mereswines, or 'sea pigs'. In those days, they were consumed a lot. There was a huge population living along the Dutch coast. Those were the days when anchovies and other small fatty fish were plentiful. The porpoises followed the fish into harbors, which is why they are officially called harbor porpoises. Porpoises grew scarcer halfway through the 20th century, however the number of sightings since 1995 have increased tremendously. The porpoise is presently the most common cetacean in the North Sea.
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Diagnostic Description

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The harbour porpoise is a chunky animal, with a blunt shortbeaked head. Placed about midway along the back is a short, wide-based, triangular dorsal fin, with small bumps on the leading edge. The flippers are small and somewhat rounded at the tips. The flukes have a concave trailing edge, divided by a prominent median notch; the tips are rounded. The straight mouthline slopes upward towards the eye. Countershading is apparent in the harbour porpoise's colour pattern; the animals are generally dark grey on the back and white on the belly. The sides are intermediate, with the border area often splotched with shades of grey. The flippers and lips are dark; there is a thin, dark grey gape-to-flipper stripe. Nineteen to 28 small, spatulate, blunt teeth line each tooth row. Can be confused with: Harbour porpoises, if seen clearly, should not be confused with any of the various species of dolphins that share their range. The other porpoise that overlaps in the North Pacific, Dall's porpoise, can be confused with this species when backlit fins are seen at a distance. However, the black and white colour pattern and slight difference in dorsal-fin shape of Dall's porpoise will be distinguishable, when seen well.
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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Benefits

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A major human threat to harbour porpoises throughout their range is incidental capture in fisheries. Many thousands are taken each year in gillnets and in certain areas, incidental catches in herring weirs, cod and salmon traps, purse seines, trawl nets, and longlines also occur. Directed fisheries have occurred in Puget Sound, the Bay of Fundy, Gulf of St. Lawrence, Labrador, Newfoundland, Greenland, Iceland, Black Sea, and the Baltic Sea. Many of these fisheries are now closed, but hunting of harbour porpoises still occurs in a few areas. Greenland and the Black Sea are the only areas where large direct catches have been reported recently. Levels of pollutants in harbour porpoise tissues have been found to be high wherever studied, probably due to the species' coastal nature. Environmental contamination has been implicated, in part, for declines in harbour porpoise populations in Europe and some parts of North America. IUCN: Insufficiently known.
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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Food and Agriculture Organization of the UN
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Brief Summary

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Most harbour porpoise groups are small, consisting of less than 8 individuals. They do, at times, aggregate into large, loose groups of 50 to several hundred animals, mostly for feeding or migration. Behaviour tends to be inconspicuous, compared to most dolphins, and harbour porpoises rarely approach boats to ride bow waves. When moving fast, they surface in a behaviour often called pop-splashing. Breaches and other leaps are rarely seen. Harbour porpoises sometimes lie at the surface for brief periods between submergences, although we do not know why they do this. Reproductive biology has been well-studied in some parts of the world. Most calves are born from spring through mid-summer. Harbour porpoises eat a wide variety of fish and cephalopods, and the main prey items appear to vary regionally. Small, non-spiny schooling fish (such as herring and mackerel) are the most common prey in many areas, and many prey species are benthic or demersal.
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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Food and Agriculture Organization of the UN
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Size

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Most adult harbour porpoises are less than 1.8 m long; maximum length is about 2 m. Females are slightly larger than males. Weights range from 45 to 70 kg for adults. Newborns are 70 to 90 cm long.
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Marine mammals of the world. Jefferson, T.A., S. Leatherwood & M.A. Webber - 1993. FAO species identification guide. Rome, FAO. 320 p. 587 figs. . 
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Harbour porpoise

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The harbour porpoise (Phocoena phocoena) is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen hundreds of kilometres from the sea. The harbour porpoise may be polytypic, with geographically distinct populations representing distinct races: P. p. phocoena in the North Atlantic and West Africa, P. p. relicta in the Black Sea and Sea of Azov, an unnamed population in the northwestern Pacific and P. p. vomerina in the northeastern Pacific.[6]

Taxonomy

The English word porpoise comes from the French pourpois (Old French porpais, 12th century), which is from Medieval Latin porcopiscus, which is a compound of porcus (pig) and piscus (fish). The old word is probably a loan-translation of a Germanic word, compare Danish marsvin and Middle Dutch mereswijn (sea swine). Classical Latin had a similar name, porculus marinus. The species' taxonomic name, Phocoena phocoena, is the Latinized form of the Greek φώκαινα, phōkaina, "big seal", as described by Aristotle; this from φώκη, phōkē, "seal".

The species is sometimes known as the common porpoise in texts originating in the United Kingdom. In parts of Atlantic Canada it is known colloquially as the puffing pig, and in Norway ‘nise’, derived from an Old Norse word for sneeze; both of which refer to the sound made when porpoises surface to breathe.

Description

Harbour porpoise skeleton on display

The harbour porpoise is a little smaller than the other porpoises, at about 67–85 cm (26+1233+12 in) long at birth, weighing 6.4–10 kg. Adults of both sexes grow to 1.4 to 1.9 m (4 ft 7 in to 6 ft 3 in). The females are heavier, with a maximum weight of around 76 kg (168 lb) compared with the males' 61 kg (134 lb). The body is robust, and the animal is at its maximum girth just in front of its triangular dorsal fin. The beak is poorly demarcated. The flippers, dorsal fin, tail fin and back are a dark grey. The sides are a slightly speckled, lighter grey. The underside is much whiter, though there are usually grey stripes running along the throat from the underside of the body.

Many anomalously white coloured individuals have been confirmed, mostly in the North Atlantic, but also notably around Turkish and British coasts, and in the Wadden Sea, Bay of Fundy and around the coast of Cornwall.[7][8][9]

Although conjoined twins are rarely seen in wild mammals, the first known case of a two-headed harbour porpoise was documented in May 2017 when Dutch fishermen in the North Sea caught them by chance.[10] A study published by the online journal of the Natural History Museum Rotterdam points out that conjoined twins in whales and dolphins are extremely rare.[11]

Distribution

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The harbour porpoise species is widespread in cooler coastal waters of the North Atlantic, North Pacific and the Black Sea.[12] In the Atlantic, harbour porpoises may be present in a curved band of water running from the coast of West Africa to the coasts of Portugal, Spain, France, the United Kingdom, Ireland, Scandinavia, Iceland, Greenland, Nova Scotia and Newfoundland and the eastern seaboard of the United States.[13][12] The population in the Baltic Sea is limited in winter due to sea freezing, and is most common in the southwest parts of the sea. There is another band in the Pacific Ocean running from the Sea of Japan, Vladivostok, the Bering Strait, Alaska, British Columbia, and California.[13][12]

The populations in these regions are not continuous[13] and are classified as separate subspecies with P. p. phocoena in the North Atlantic and West Africa, P. p. relicta in the Black Sea and Sea of Azov, an unnamed population in the northwest Pacific and P. p. vomerina in the northeast Pacific.[6][12]

Concerning the North Atlantic, an international workshop co-organised by the North Atlantic Marine Mammal Commission and the Norwegian Institute of Marine Research reviewed the status of the species in 2018. It concluded that the harbour porpoise population structure is more complex than previously thought, with at least three genetically distinct subspecies in the North Atlantic. Given the structure of the harbour porpoise population, the workshop delineated 18 assessment areas for the North Atlantic.[14]

Population status

The harbour porpoise has a global population of at least 700,000.[12] In 2016, a comprehensive survey of the Atlantic region in Europe, from Gibraltar to Vestfjorden in Norway, found that the population was about 467,000 harbour porpoises, making it the most abundant cetacean in the region, together with the common dolphin.[15] Based on surveys in 1994, 2005 and 2016, the harbour porpoise population in this region is stable.[15] The highest densities are in the southwestern North Sea and oceans of mainland Denmark;[15] the latter region alone is home to about 107,000-300,000 harbour porpoises.[16][17] The entire North Sea population is about 335,000.[18] In the Western Atlantic it is estimated that there are about 33,000 harbour porpoises along the mid-southwestern coast of Greenland (where increasing temperatures have aided them),[12] 75,000 between the Gulf of Maine and Gulf of St. Lawrence, and 27,000 in the Gulf of St. Lawrence.[3] The Pacific population off mainland United States is about 73,000 and off Alaska 89,000.[3] After sharp declines in the 20th century, populations have rebounded in the inland waters of Washington state.[19] In contrast, some subpopulations are seriously threatened. For example, there are less than 12,000 in the Black Sea,[3] and only about 500 remaining in the Baltic Sea proper, representing a sharp decrease since the mid-1900s.[20]

Natural history

A harbour porpoise off Denmark

Ecology

Harbour porpoises prefer temperate and subarctic waters.[13] They inhabit fjords, bays, estuaries and harbours, hence their name.[13] They feed mostly on small pelagic schooling fish, particularly herring, pollack, hake, sardine, cod,[21] capelin, and sprat.[12] They will, however, eat squid and crustaceans in certain places.[12] This species tends to feed close to the sea bottom, at least for waters less than 200 metres (110 fathoms) deep.[12] However, when hunting sprat, porpoise may stay closer to the surface.[12] When in deeper waters, porpoises may forage for mid-water fish, such as pearlsides.[12] A study published in 2016 showed that porpoises off the coast of Denmark were hunting 200 fish per hour during the day and up to 550 per hour at night, catching 90% of the fish they targeted.[22][23] Almost all the fish they ate were very small, between 3 and 10 cm (1–4 in) long.[22][23]

Harbour porpoises tend to be solitary foragers, but they do sometimes hunt in packs and herd fish together.[12] Young porpoises need to consume about 7% to 8% of their body weight each day to survive, which is approximately 15 pounds or 7 kilograms of fish. Significant predators of harbour porpoises include white sharks and killer whales (orcas). Researchers at the University of Aberdeen in Scotland have also discovered that the local bottlenose dolphins attack and kill harbour porpoises without eating them due to competition for a decreasing food supply.[24] An alternative explanation is that the adult dolphins exhibit infanticidal behaviour and mistake the porpoises for juvenile dolphins which they are believed to kill.[25] Grey seals are also known to attack harbour porpoises by biting off chunks of fat as a high energy source.[26]

Behaviour, reproduction and life-span

Some studies suggest porpoises are relatively sedentary and usually do not leave a certain area for long.[12] Nevertheless, they have been recorded to move from onshore to offshore waters along coast.[12] Dives of 220 metres (120 fathoms) by harbour porpoises have been recorded.[12] Dives can last five minutes but typically last one minute.[27]

The social life of harbour porpoises is not well understood. They are generally seen as a solitary species.[13] Most of the time, porpoises are either alone or in groups of no more than five animals.[13] Porpoises mate promiscuously.[12] Males produce large amounts of sperm, perhaps for sperm competition.[12] Females become sexually mature by their third or fourth year and can calve each year for several consecutive years, being pregnant and lactating at the same time. The gestation of the porpoise is typically 10–11 months.[13] Most births occur in late spring and summer.[12] Calves are weaned after 8–12 months.[13] Their average life-span is 8–13 years, although individuals have reached 20.[12][28] In a study of 239 dead harbour porpoises in the Gulf of Maine–Bay of Fundy, the vast majority were less than 12 years old and the oldest was 17.[29]

Threats

Dead porpoise ashore

Hunting

Harbour porpoises were traditionally hunted for food, as well as for their blubber, which was used for lighting fuel. Among others, hunting occurred in the Black Sea, off Normandy, in the Bay of Biscay, off Flanders, in the Little Belt strait, off Iceland, western Norway, in Puget Sound, Bay of Fundy and Gulf of Saint Lawrence.[3][30][31] The drive hunt in the Little Belt strait is the best documented example. Thousands of porpoises were caught there until the end of the 19th century, and again in smaller scale during the world wars.[32] Currently, however, this species is not subject to commercial hunting, but it is hunted for food and sold locally in Greenland.[3] In prehistoric times, this animal was hunted by the Alby People of the east coast of Öland, Sweden.

Interactions with fisheries

A harbour porpoise in captivity in Denmark. The individuals at the center were rescued[33] after being injured following entanglement in fishing gear, showing the danger nets can represent to the species[34]

The main threat to porpoises is static fishing techniques such as gill and tangle nets. Bycatch in bottom-set gill nets is considered the main anthropogenic mortality factor for harbour porpoises worldwide. Several thousand die each year in incidental bycatch, which has been reported from the Black Sea, the Baltic Sea, the North Sea, off California, and along the east coast of the United States and Canada.[3] Bottom-set gill nets are anchored to the sea floor and are up to 23 kilometres (12+12 nautical miles) in length. It is unknown why porpoises become entangled in gill nets, since several studies indicate they are able to detect these nets using their echolocation.[35][36] Porpoise-scaring devices, so-called pingers, have been developed to keep porpoises out of nets and numerous studies have demonstrated they are very effective at reducing entanglement.[37][38] However, concern has been raised over the noise pollution created by the pingers and whether their efficiency will diminish over time due to porpoises habituating to the sounds.[34][39]

Mortality resulting from trawling bycatch seems to be less of an issue, probably because porpoises are not inclined to feed inside trawls, as dolphins are known to do.

Overfishing

Overfishing may reduce preferred prey availability for porpoises. Overfishing resulting in the collapse of herring in the North Sea caused porpoises to hunt for other prey species.[40] Reduction of prey may result from climate change, or overfishing, or both.

Noise pollution

Noise from ship traffic and oil platforms is thought to affect the distribution of toothed whales, like the harbour porpoise, that use echolocation for communication and prey detection. The construction of thousands of offshore wind turbines, planned in different areas of North Sea, is known to cause displacement of porpoises from the construction site,[41] particularly if steel monopile foundations are installed by percussive piling, where reactions can occur at distances of more than 20 km (11 nmi).[42] Noise levels from operating wind turbines are low and unlikely to affect porpoises, even at close range.[43][44]

Pollution

Marine top predators like porpoises and seals accumulate pollutants such as heavy metals, PCBs and pesticides in their fat tissue. Porpoises have a coastal distribution that potentially brings them close to sources of pollution. Porpoises may not experience any toxic effects until they draw on their fat reserves, such as in periods of food shortage, migration or reproduction.

Climate change

An increase in the temperature of the sea water is likely to affect the distribution of porpoises and their prey, but has not been shown to occur. Reduced stocks of sand eel along the east coast of Scotland, a pattern linked to climate change, appears to be the main reason for the increase in malnutrition in porpoises in the area.[45]

Conservation status

Overall, the harbour porpoise is not considered threatened and the total population is in the hundreds of thousands.[3]

The harbour porpoise populations of the North Sea, Baltic Sea, western North Atlantic, Black Sea and North West Africa are protected under Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS).[46] In 2013, the two Baltic Sea subpopulations were listed as vulnerable and critically endangered respectively by HELCOM.[47] Although the species overall is considered to be of Least Concern by the IUCN,[3] they consider the Baltic Sea and Western African populations critically endangered, and the subspecies P. p. relicta of the Black Sea endangered.[48][49][50]

In addition, the harbour porpoise is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).

See also

References

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  2. ^ "Fossilworks Phocoena phocoena". John Alory.
  3. ^ a b c d e f g h i Braulik, G.; Minton , G.; Amano, M.; Bjørge, A. (2020). "Phocoena phocoena". IUCN Red List of Threatened Species. 2020: e.T17027A50369903. doi:10.2305/IUCN.UK.2020-2.RLTS.T17027A50369903.en. Retrieved 12 November 2021.
  4. ^ Group, Species account by IUCN SSC Cetacean Specialist; Team, regional assessment by European Mammal Assessment (26 January 2007). "IUCN Red List of Threatened Species: Phocoena phocoena". IUCN Red List of Threatened Species.
  5. ^ IUCN (International Union for Conservation of Nature) 2008. Phocoena phocoena. In: IUCN 2015. The IUCN Red List of Threatened Species. Version 2015.2. http://www.iucnredlist.org. Downloaded on 25 July 2015.
  6. ^ a b Shirihai, Hadoram; Jarrett, Brett (2006). Whales, Dolphins and Seals - A Field Guide to the Marine Mammals of the World. A&C Black Publishers. ISBN 978-0-7136-7037-0.
  7. ^ Tonaya, M.A.; Bilginc, S.; Dedea, A. Akkayab A.; Yeşilçiçekc, T.; Kösec, Ö.; Ceylanc, Y. (2012). "First records of anomalously white harbour porpoises (Phocoena phocoena) in the Turkish seas with a global review". Hystrix: The Italian Journal of Mammalogy. 23 (2). doi:10.4404/hystrix-23.2-4792. Archived from the original on 4 March 2016. Retrieved 8 July 2014.
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  35. ^ Kastelein, R.; Au, W. W. L. (2000). "Detection distances of bottom-set gill nets by harbour porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops truncatus)". Mar.Environm.Res. 49 (4): 359–375. doi:10.1016/s0141-1136(99)00081-1. PMID 11285736.
  36. ^ Villadsgaard, A.; Wahlberg, M.; Tougaard, J. (2007). "Echolocation signals of free-ranging harbour porpoises, Phocoena phocoena". J. Exp. Biol. 210 (1): 56–64. doi:10.1242/jeb.02618. PMID 17170148. S2CID 6184532.
  37. ^ Kraus, S. D.; Read, A. J.; Solow, A.; Baldwin, K.; Spradlin, T.; Anderson, E.; Williamson, J. (1997). "Acoustic alarms reduce porpoise mortality". Nature. 388 (6642): 525. Bibcode:1997Natur.388..525K. doi:10.1038/41451. S2CID 4412647.
  38. ^ Larsen, F (1999). The effect of acoustic alarms on the by-catch of harbour porpoises in the Danish North Sea gill net fishery. Paper SC/51/SM41 presented to the IWC Scientific Committee
  39. ^ Cox, T. M.; Read, A. J.; Solow, A.; Tregenza, N. (2001). "Will harbour porpoises (Phocoena phocoena) habituate to pingers?". J.Cetacean.Res.Manage. 3 (1): 81–86.
  40. ^ Santos, M.; Pierce, G. (1 January 2003). "The diet of harbour porpoise (Phocoena phocoena) in the Northeast Atlantic". Oceanogr Mar Biol Annu Rev. 41: 355–390.
  41. ^ Carstensen, J.; Henriksen, O. D.; Teilmann, J. (2006). "Impacts on harbour porpoises from offshore wind farm construction: Acoustic monitoring of echolocation activity using porpoise detectors (T-PODs)". Mar. Ecol. Prog. Ser. 321: 295–308. doi:10.3354/meps321295.
  42. ^ Tougaard, J.; Carstensen, J.; Teilmann, J.; Skov, H.; Rasmussen, P. (2009). "Pile driving zone of responsiveness extends beyond 20 km for harbour porpoises (Phocoena phocoena, (L.))". J. Acoust. Soc. Am. 126 (1): 11–14. Bibcode:2009ASAJ..126...11T. doi:10.1121/1.3132523. PMID 19603857.
  43. ^ Madsen, P. T.; Wahlberg, M.; Tougaard, J.; Lucke, K.; Tyack, P. L. (2006). "Wind turbine underwater noise and marine mammals: Implications of current knowledge and data needs". Mar. Ecol. Prog. Ser. 309: 279–295. Bibcode:2006MEPS..309..279M. doi:10.3354/meps309279.
  44. ^ Tougaard, J.; Henriksen, O. D.; Miller, L. A. (2009). "Underwater noise from three offshore wind turbines: estimation of impact zones for harbor porpoises and harbor seals". J. Acoust. Soc. Am. 125 (6): 3766–3773. doi:10.1121/1.3117444. PMID 19507958.
  45. ^ MacLeod, Colin D; Santos, M. Begoña; Reid, Robert J; Scott, Beth E; Pierce, Graham J (9 January 2007). "Linking sandeel consumption and the likelihood of starvation in harbour porpoises in the Scottish North Sea: could climate change mean more starving porpoises?". Biology Letters. 3 (2): 185–8. doi:10.1098/rsbl.2006.0588. PMC 2375924. PMID 17251125.
  46. ^ "Appendix II Archived 21 February 2012 at the Wayback Machine" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
  47. ^ HELCOM (2013). "HELCOM Red List of Baltic Sea species in danger of becoming extinct" (PDF). Baltic Sea Environmental Proceedings (140): 92. Archived from the original (PDF) on 7 October 2014. Retrieved 3 August 2014.
  48. ^ Hammond, P.S.; Bearzi, G.; Bjørge, A.; Forney, K.; Karczmarski, L.; Kasuya, T.; Perrin, W.F.; Scott, M.D.; Wang, J.Y.; Wells, R.S.; et al. (2008). "Phocoena phocoena (Baltic Sea subpopulation)". IUCN Red List of Threatened Species. 2008. Retrieved 1 June 2017.old-form url
  49. ^ Birkun Jr.; A.A.; Frantzis, A. (2008). "Phocoena phocoena ssp. relicta". IUCN Red List of Threatened Species. 2008: e.T17030A6737111. doi:10.2305/IUCN.UK.2008.RLTS.T17030A6737111.en. Retrieved 12 November 2021.
  50. ^ "Phocoena phocoena". Convention on the Conservation of Migratory Species of Wild Animals. Retrieved 1 June 2017.
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Harbour porpoise: Brief Summary

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The harbour porpoise (Phocoena phocoena) is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen hundreds of kilometres from the sea. The harbour porpoise may be polytypic, with geographically distinct populations representing distinct races: P. p. phocoena in the North Atlantic and West Africa, P. p. relicta in the Black Sea and Sea of Azov, an unnamed population in the northwestern Pacific and P. p. vomerina in the northeastern Pacific.

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Biology

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Harbour porpoises live either solitarily or in groups, normally of three to five individuals, although sometimes more. Normally individual porpoises or couples (mother and calf) are observed and high numbers can be seen during migrations. Like dolphins, the harbour porpoise orientates itself by means of echo-sounding or ‘sonar’. It has a particular way of swimming with a ‘rolling’ movement (imagine a turning wheel); part of the back, including the dorsal fin surfaces briefly before re-entering the water giving the appearance of a rotating motion. This movement will normally be repeated three to four times, prior to a long dive. The diet of an adult harbour porpoise is made up of various pelagic and demersal fish, as well as invertebrates. In the Southern North Sea, it consists mainly of small benthic fish, herring, cephalopod, whiting and cod. A daily meal would normally consist of about 5 kilos fish (around 10% of the body

Reference

Stienen, E.W.M.; Van Waeyenberge, J.; Kuijken, E. (2003). Zeezoogdieren in Belgisch mariene wateren [Marine mammals in Belgian marine waters]. Rapport Instituut voor Natuurbehoud, A.2003.152. Instituut voor Natuurbehoud: Brussel, Belgium. 15 pp.

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Diet

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Variety of inshore and offshore fish, herring, mackerel, and anchovy. Krill when young.

Reference

North-West Atlantic Ocean species (NWARMS)

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Distribution

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East Pacific; Eastern Atlantic Ocean; Indo-West Pacific; Western Atlantic Ocean

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North-West Atlantic Ocean species (NWARMS)

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Habitat

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cool temperate and subpolar, mostly in shallow water

Reference

van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).

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Habitat

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inshore and offshore

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North-West Atlantic Ocean species (NWARMS)

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IUCN Red List Category

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Least Concern (LC)

Reference

IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.

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Perrin, William [email]

IUCN Red List Category

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Subpopulation Baltic Sea harbour porpoise : Critically Endangered (CR)

Reference

IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.

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Morphology

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Distinguishing characteristics: Dives without lifting tail. Blow not readily visible. Triangular dorsal fin. Spoon-shaped teeth. Blunt snout. Colour is grey above with white belly.

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North-West Atlantic Ocean species (NWARMS)

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Morphology

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The head is blunt. Depending on the light, the back may appear black, grey or brown). The flanks are grey and the underside is white. The pectoral fins are black. A dark line runs from the corner of the mouth to the flipper. The more or less triangular small dorsal fin is positioned in the centre of the back. The upper back and dorsal fin are the only features one normally gets to see of a swimming harbour porpoise. The chief characteristics are its small size, the blunt head and the small triangular dorsal fin.

Reference

Stienen, E.W.M.; Van Waeyenberge, J.; Kuijken, E. (2003). Zeezoogdieren in Belgisch mariene wateren [Marine mammals in Belgian marine waters]. Rapport Instituut voor Natuurbehoud, A.2003.152. Instituut voor Natuurbehoud: Brussel, Belgium. 15 pp.

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