Delphinus delphis, Linnaeus, 1758
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publication ID |
https://doi.org/ 10.5281/zenodo.6610922 |
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DOI |
https://doi.org/10.5281/zenodo.6608640 |
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persistent identifier |
https://treatment.plazi.org/id/BD4CCC61-7622-FFE9-FFC6-FE48E55AFAF0 |
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treatment provided by |
Diego |
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scientific name |
Delphinus delphis |
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10. View On
Short-beaked Common Dolphin
French: Dauphin commun / German: Gewohnlicher Delfin / Spanish: Delfin de hocico corto
Other common names: Atlantic Dolphin, Common Dolphin, Criss-cross Dolphin, Pacific Dolphin, Saddle-backed Dolphin, Short-beaked Saddleback Dolphin, White-bellied Porpoise; Black Sea Common Dolphin (ponticus)
Taxonomy. Delphinus delphis Linnaeus, 1758 View in CoL ,
“Oceano Europzo.”
Only a single species, D. delphis , was recognized before 1994 when it was split into D. delphis and D. capensis . Nevertheless, taxonomy of D. delphis is currently uncertain. There is a distinct form in the Black Sea that is distinguished by skull morphology and microsatellite DNA that is classified as a subspecies, although its taxonomic status is still unclear. There is also a genetically divergent population in the Mediterranean Sea, but it is not classified as a separate subspecies. Two subspecies recognized.
Subspecies and Distribution.
D. d. ponticus Barabash-Nikiforov, 1935 — Black Sea and adjoining Marmara Sea, excluding Sea of Azov. View Figure
Descriptive notes. Total length 170-230 cm (males) and 160-220 cm (females); weight up to 200 kg. Neonates are 80-93 cm long. Individual Short-beaked Common Dolphins in the north-eastern Atlantic Ocean are slightly larger and be up to 270 cm total body length. The Short-beaked Common Dolphin has moderately tall, falcate dorsal fin with a pointed tip. It has slightly more robust build and shorter beak than the Long-beaked Common Dolphin ( D. capensis ) and has more rounded melon. Flippers are small and slender, with pointed tips. Some adults, likely males, possess post-anal protrusion. Dorsal surface of body is dark brown or gray, which contrasts white belly. Flanks have distinct hourglass pattern consisting of yellowish or ocher anterior patch and pale-gray patch on tailstock. Midpoint of hourglass shape occurs below dorsal fin. Flippers and dorsal fin may range in color from almost white to dark gray, although dorsal fin will often have paler central patch. Lips are black, and dark stripe extends from chin below mouth to flipperjoint. Another dark stripe runs along crease between beak and melon and extends posteriorly to encircle eyes. Pale stripe runs along forehead from anterior apex of melon to blowhole. Young Short-beaked Common Dolphins tend to have more muted color pattern. There is a rare color morph where the usually yellowish thoracic patch is dark gray. Each jaw contains 41-57 pairs of sharp, conical teeth. The “Black Sea Common Dolphin” (D. d. ponticus) is a dwarf form that has a maximum length of 219 cm; average length is ¢.162 cm for males and 158 cm for females. This form also has shorter beak than nominate form, containing fewer teeth, 41-52 pairs in each jaw.
Habitat. Tends to be more common in offshore than near-shore waters and generally not found in areas less than 180 m deep. The Short-beaked Common Dolphin is especially abundant in regions associated with strong upwelling, such as over continental shelves or regions where seafloor is steep and sloping. Preferred surface temperature seems to be 10-20°C, and groups may occasionally follow warm water currents outside of its usual latitudinal distribution. The Short-beaked Common Dolphin is rare or absent throughout most of the Indian Ocean and tropical and subtropical Atlantic Ocean, and it is not known to occur in the Caribbean Basin or Gulf of Mexico. The Black Sea Common Dolphin tends to prefer more offshore waters with lower salinity, but it will seasonally follow migrating prey species into more near-shore water.
Food and Feeding. The Short-beaked Common Dolphin feeds primarily on small, schooling, mesopelagic fish and squid such as scombroids (e.g. mackerel), clupeoids (e.g. herring), and California market squid ( Doryteuthis opalescens). In the Western Atlantic Ocean, oceanic populations tend to have diets more dominated with cephalopods than near-shore populations. North Atlantic populations of Short-beaked Common Dolphins prefer myctophid fish (lanternfish), and diets of South African populations tend to be dominated by South African pilchard ( Sardinops sagax ocellatus). Off eastern New Zealand, Short-beaked Common Dolphins prefer yellowtail horse mackerel (Trachurus novaezelandiae), kahawai (Arripis trutta), yellow-eyed mullet ( Aldrichetta forsteri), flying fish ( Cheilopogon pinnatibarbatus), parore (Girella tricuspidata), and garfish (Hyporamphus thi). In some areas, such as off southern California, Short-beaked Common Dolphins feed nocturnally in association with the rising deep scattering layer. Anchovies ( Engraulidae ) and squid are dominant prey in winter, and smelt ( Argentinidae ) and lanternfish are dominant in spring and summer. Short-beaked Common Dolphins sometimes forage cooperatively, and foraging dives up to 200 m have been recorded.
Breeding. In the North Pacific Ocean, breeding of the Short-beaked Common Dolphin peaks in spring and summer; it peaks in summer in the Black Sea. Minimal sexual dimorphism and large testes size relative to body size in males suggests a promiscuous mating system dependent on sperm competition. In the eastern Pacific and western Atlantic oceans, sexual maturity is reached at 6-8 years in females and 7-12 years in males. The Black Sea Common Dolphin appears to reach sexual maturity much earlier at 2-4 years in females and c.3 years in males. Reproductive females will have an offspring every 1-3 years but may occasionally become pregnant while still lactating. Gestation is 10-11-7 months. Longevity is thought to be ¢.30 years for both sexes.
Activity patterns. The Short-beaked Common Dolphin can be aerially active, especially in large groups; they frequently leap out of the water while traveling. They also will bow-ride vessels and sometimes even large mysticetes.
Movements, Home range and Social organization. Group sizes of Short-beaked Common Dolphins are ¢.10-10,000 individuals. Larger groups consist of smaller subgroups that are likely segregated by sex and age classes. The Short-beaked Common Dolphin has been observed in mixed-species groups with Risso’s Dolphin ( Grampus griseus ), pilot whales ( Globicephala spp. ), the Striped Dolphin ( Stenella coeruleoalba ), and various species of Lagenorhynchus . In the eastern tropical Pacific Ocean, they also occasionally associate with yellowfin tuna ( Thunnus albacares), making them susceptible to the tuna purse-seine industry. In some regions, abundance is known to vary seasonally. Off southern California, for example, the Short-beaked Common Dolphin is most abundant in summer through autumn and in mid-winter. These populations seem to prefer traveling over underwater escarpments in a north-south direction along the western Californian and Mexican coasts. Off New Zealand, sea-surface temperature may affect seasonal movements; Short-beaked Common Dolphins occur ¢.9-2 km offshore in spring and summer but 20-3 km off shore in autumn. This movement is likely correlated with migrating temperature-dependent prey species. Movements have also been associated with temperature in the western North Atlantic Ocean, where Short-beaked Common Dolphins are most abundant in nearshore Nova Scotia in July, coincident with seasonalrising sea-surface temperature.
Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. The subpopulation of Short-beaked Common Dolphins in the Mediterranean Sea is classified as Endangered because it has suffered a marked decline and has almost completely disappeared from large portions ofits former range (e.g. Provencal Basin, Balearic Sea, Ligurian Sea, and northern Adriatic Sea). The Black Sea Common Dolphin is classified as Vulnerable. No estimates of total abundance of the Short-beaked Common Dolphin are currently available, but there are ¢.2,963,000 individuals in the eastern tropical Pacific Ocean, ¢.352,000 individuals off western USA, ¢.63,400 individuals in European continental shelf waters, ¢.121,000 individuals in the western North Atlantic Ocean, and ¢.19,400 individuals in the western Mediterranean Sea. Several populations face local threats, but as a whole, the Short-beaked Common Dolphin is abundant and likely not declining. The population in the Mediterranean Sea, however, has been in sharp decline over the last few decades, especially in the northern Adriatic and eastern Ionian seas. Although now directly caught in only a few fisheries (mainly Japanese), the Short-beaked Common Dolphin was hunted historically until the 1980s and 1990s in Turkey, the USSR, Peru, Spain, and France.Its greatest threat currently is incidental catch. In fact, the Short-beaked Common Dolphin is one of the most common species in bycatch in pelagic purse-seine and drift-net fisheries, due to its abundance and association with large pelagic fish such as tuna. Catch limits imposed by the Inter-American Tropical Tuna Commission and resulting emphasis on dolphin release and safety gear have probably reduced mortality of Short-beaked Common Dolphins in tuna purse-seine fisheries by 97% since 1986 (incidental take was 24,307 individuals that year). This fishery killed only 325 Short-beaked Common Dolphins in 2005. Between 1990 and 2002, 21,000 Shortbeaked Common Dolphins were killed in pelagic driftnetfisheries targeting broadbill swordfish (Xiphias gladius) and common thresher shark (Alopias vulpinus) off California. Acoustic “pingers” may be effective in deterring marine mammals, including the Short-beaked Common Dolphin, from these driftnets. Large-scale driftnet fishing that targets broadbill swordfish still occurs illegally on the Mediterranean side of the Strait of Gibraltar, where 12,000-15,000 Short-beaked Common Dolphins are killed per year; most of the fleet operates from Morocco. For Short-beaked Common Dolphins, this take likely exceeds 10% of the local population size, making it unsustainable. The Short-beaked Common Dolphin is also killed incidentally in small-scale gillnet, trawl, and purse-seine fisheries throughout its distribution, including Black Sea, Mediterranean Sea, off north-western Africa, South America, New Zealand, and north Atlantic Ocean. Off northern Portugal, 52% of common dolphin strandings are due to either confirmed bycatch or harmful interactions with fishing gear, contributing to an estimated 44% of the local population’s mortality. High rates of bycatch of Short-beaked Common Dolphins also occur in UK and French pelagic pair-trawl sea bass fisheries. Although small-scale, these fisheries are estimated to have killed at least 800 dolphins in 2000-2005. The southern Australia population of the Short-beaked Common Dolphin, which appears to be genetically distinct from the nearby Tasmanian population, may be especially vulnerable to incidental catch in local purse-seine fisheries. In 2004-2005, for example, 377 Short-beaked Common Dolphins were killed in only seven months. Considering the population’s genetic distinctness, this catch rate may not be sustainable. The Short-beaked Common Dolphin is currently rare in the Adriatic Sea and has likely been steadily declining since the 1800s due to culling campaigns, which continued into the 1960s, and to more recent habitat degradation. Heavy metal and organochlorine contamination may also be a problem in some areas. For example, there are high PCB concentrations in c.40% of female Short-beaked Common Dolphins in the Atlantic Ocean off Europe. High concentrations of cadmium have also been documented in kidneys of Shortbeaked Common Dolphins off South Australia, and they have been correlated with various pathological problems such as proteinuria (excess serum proteins in urine). Overfishing of prey species (primarily anchovy and sprat) is a major threat to Shortbeaked Common Dolphins in the Black and Mediterranean seas. There is no reliable estimate of abundance for the Black Sea Common Dolphin. At least 159,000-161,000 Black Sea Common Dolphins were killed in 1962-1983 before Turkey banned small cetacean hunting. Priorto this, from the 1930s to the 1960s, the USSR, Romania, and Bulgaria took c.1-5 million Black Sea Common Dolphins before commercial hunting of small cetaceans was banned by these countries in 1966. Black Sea Common Dolphins are also threatened by habitat degradation and overfishing of prey species, which likely increased their susceptibility to infection during a morbillivirus epizootic in 1994. Decline of the Black Sea Common Dolphin has been inferred based on the combined impact of these threats.
Bibliography. Bearzi, Holcer & Notarbartolo di Sciara (2004), Bearzi, Politi, Agazzi & Azzellino (2006), Bearzi, Politi, Agazzi, Bruno et al. (2005), Bearzi, Reeves et al. (2003), Bilgmann et al. (2008), Birkun (2008), Birkun et al. (1999), Canadas & Hammond (2008), Carretta et al. (2004), Crespo et al. (2000), Danil & Chivers (2007), De Boer et al. (2008), Evans (1994), Frantzis & Herzing (2002), Hammond et al. (2008g), Jefferson & Van Waerebeek (2002), Jefferson, Fertl et al. (2009), Jefferson, Webber & Pitman (2008), Kuiken et al. (1994), Long et al. (1997), Murphy et al. (2005), Natoli et al. (2006), Neumann (2001), Neumann & Orams (2003), Perrin (2009d), Pierce et al. (2008), Pusineri et al. (2007), Rogan & Mackey (2007), Silva (1999), Silva & Sequieira (2003), Tudela et al. (2005), Waring et al. (2008), Westgate & Read (2007).
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