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Atlantic white-sided dolphin

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See also: Pacific white-sided dolphin

Atlantic white-sided dolphin
Size compared to an average human
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus
Gray, 1846
Species:
L. acutus
Binomial name
Lagenorhynchus acutus
(Gray, 1828)
  Atlantic white-sided dolphin range

The Atlantic white-sided dolphin (Lagenorhynchus acutus) is a distinctively coloured dolphin found in the cool to temperate waters of the North Atlantic Ocean.

Description

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An Atlantic white-sided dolphin off the coast of Cape Ann, Massachusetts

The Atlantic white-sided dolphin is built slightly 'thicker' compared to other oceanic dolphins; they are nearly indistinguishable from the Pacific white-sided dolphin, despite the fact that they are only very distantly related phylogenetically.[3] At birth, calves measure just over a meter long; adult males grow to about 2.8 m (9.2 ft), and females to about 2.5 m (8.2 ft),[4] weighing between 180–230 kg (400- 510 lb) once fully grown.[4] Females reach sexual maturity between the ages of 6 and 12 years, and males between 7 and 11 years old.[5][6] The gestation period is 11 months and lactation lasts for about 18 months — both typical figures for dolphins.[4] Atlantic white-sided dolphins are known to live for at least 17 years.[4]

The key distinguishing feature is the dolphin's coloration—a white to pale-yellow patch is found behind the dorsal fin on both sides of the body.[4] The white-sided dolphin's color variations are unique amongst the standard hues of white, grey, black and blue seen on other pelagic cetaceans.[4] Their body's coloration is well-demarcated, with the chin, throat and belly being white; the flippers, dorsal fin and back are dark-grey to black (with the exception of the yellow patch), and there is a further white patch below the dorsal fin (lying above a lighter, grayish stripe running from the beak, above the eye, down to the tail stock).[4]

Dolphin pod sizes vary by location, with groups averaging 60 in number having been seen close to the Newfoundland coastline, but somewhat smaller east of Iceland.[4] From the analysis of the stomach contents of stranded animals, fishes, such as herring and mackerel, and squid appear to be the species' main prey.[4] The Atlantic white-sided dolphin is fairly acrobatic, and keen to interact with boats; however, it is not as wildly gregarious as the white-beaked, bottlenose or common dolphins.[4]

Geographic range and distribution

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The species is endemic to the northern Atlantic Ocean.[4] The distribution limits are the Norwegian Sea in the northeast, the Davis Strait in the northwest, coastal North Carolina in the southwest and the Celtic Sea in the southeast (with possible range extension south to the Azores).[4] Areas of particularly high population density include the shores of Newfoundland and Cape Cod, the triangular area of sea between the United Kingdom, Iceland and Greenland and the northern North Sea.[7][8][9] In 2008, sightings of Atlantic white-sided dolphins, as well as the melon-headed whale, were documented off South Carolina after a few strandings had taken place in the area at the time.[10] Along the North American east coast the species tends to occur in continental shelf waters, around 100m in depth,[11] and seem to show a preference toward areas of steep slopes and canyons.[12][13] They are associated with the colder, slightly less saline waters in the northern Atlantic, compared to for example common dolphins that are found in warmer, slightly more saline waters of the North Atlantic, though it is unclear whether this is due to preferences or if these factors influence prey supply.[14][15]

Behaviour

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Foraging

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The diet of Atlantic white-sided dolphins mainly consists of herring, hake and squid.[4] However, as opportunistic carnivores, they consume a large variety of prey, including smaller mackerel and various bottom-dwelling fish.[4] They have been observed cooperatively hunting at the surface.[4] It has been suggested that larger groups split while feeding.[12]

Social behaviour

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Like all species of the dolphin family, Atlantic white-sided dolphins are very social animals, often traveling in large pods and displaying aerial behaviors as they travel.[16] The pod's size can vary, from several dozen to several hundred individuals, though the average size is around 50.[17] However, studies have shown there to be little familial relation between members of a group, appearing more as a social pod traveling for "safety in numbers". Researchers in different parts of their range have found that individuals were, mostly, unrelated to one another.[18][19] Juveniles spend at least some time in separate social groups, away from their parents, prior to weaning.[4] Atlantic white-sided dolphins jump and breach more frequently when in larger groups, as this behaviour might have a social context.[16] They have a wide vocal repertoire which includes squeals, whistles, clicks and buzzes.[17][20] It is suggested that vocalisation is used for communication as noise production increases during socialising.[20]

Despite being docile creatures, even known to interact with various species of cetacean in a nonviolent manner, most notably with the long-finned pilot whale (Globicephala melas),[21] they have also been known to display violent behavior towards harbor porpoises, attacking them until they eventually succumb to their wounds (a similar behavior as observed in bottlenose dolphins).[22][23]

Migration

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Atlantic white-sided dolphins do not undertake specific seasonal migration.[12] However, they do move within their home range following prey distribution.[12] For example, in the waters off eastern North America this species moves southwards in winter and spring.[4][8]

Reproduction

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Most of the calves are born around June and July.[4] The gestation period is 11 months and lactation around 18 months.[4] The birth interval varies between 1–3 years.[11]

Females reach sexual maturity around the age of 6–12 years.[5] Males reach sexual maturity around 7–11 years.[6] The reproduction is most likely seasonal, beginning in February, as some studies have identified dormant testes in some males.[6]

Taxonomy

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3d model of skeleton

The Atlantic white-sided dolphin was named by John Edward Gray in 1828. The specific name acutus comes from the Latin for 'pointed' and refers to the sharply pointed dorsal fin.[4] It is traditionally placed in the genus Lagenorhynchus, but there is consistent molecular evidence that supports the Atlantic white-sided dolphin and the white-beaked dolphin as basal members of the family Delphinidae and not closely related.[3] It has therefore been proposed to move the Atlantic white-sided dolphin to its own genus, Leucopleurus.[24]

Population status

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The estimations for the U.S. shelf and shelf-edge water suggest that the population size is about 300,000.[4] Additional 120,000 individuals have been estimated to spend summer in the Gulf of St.Lawrence.[4] In the eastern North America waters the numbers increase southwards in winter and spring in association with cold waters from the Gulf of Maine.[4] Two projects attempted to estimate the population trends - multinational Small Cetacean Abundance in the North Sea and Adjacent Waters (SCANS) survey project and the North Atlantic Sightings Survey (NASS). SCANS surveys, however, failed to produce species specific estimation as it combined both white-sided and white-beaked dolphins. NASS surveys did not indicate any population trends.

Threats

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Hvalba, Faroe Islands in August 2006

Whaling

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Historically, Atlantic white-sided dolphins were killed in drives conducted from Norway and Newfoundland.[25] These have ceased in recent years, although they still occur to a lesser extent from the Faroe Islands, where the meat and blubber are in high regard as food.[26] Reported catches in the years vary, though individual years suddenly stand out, such as in 2002, where the number reported killed was 773,[27] and in 2017, when 488 were killed.[26] In September 2021, a large pod of 1,428 animals was herded in Skálafjördur and killed.[28]

Annual number taken of white-sided dolphin in the Faroe Islands in the period 1980-2009 [27]
Year No/yr drive/yr Year No/yr drive/yr Year No/yr drive/yr
1980 8 1 1993 377 6 2001 546 7
1983 10 1 1994 263 7 2002 773 10
1985 32 1 1995 157 4 2003 186 5
1986 185 4 1996 357 7 2004 333 5
1987 76 2 1997 350 10 2005 312 4
1988 603 4 1998 438 4 2006 622 8
1990 55 2 1998 438 4 2008 1 1
1992 47 3 2000 265 3 2009 171 5

Entanglement and by catch

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Atlantic white-sided dolphins have also been killed in incidental catch situations in the fishing industry. Such occurrences have been reported in Canada, United States, United Kingdom and Ireland.[1] Between 1977 and 1988, 13 Atlantic white-sided dolphins were reported as being incidentally caught in the Northeastern United States by U.S fisheries observers, 11 of these in Mackerel fisheries.[29] They have also been reported to get caught in pelagic or near surface trawl or drift nets.[12][17]

Noise

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Anthropogenic underwater noise is a potential disturbance to Atlantic white-sided dolphins as they use sounds to communicate and catch prey.[20] A survey done in the UK showed that the sighting rate of Atlantic white-sided dolphins declines when airguns were firing compared to when they were not.[20]

Pollution

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Persistent organic pollutants (POPs) such as PCBs and organochlorine pesticides (e.g. DDT, DDE) and polybrominated diphenyl ether (PBDE) flame retardants have been identified in body tissues of Atlantic white-sided dolphins throughout their range.[7][30][31][32] Males had higher levels of PCBs suggesting that females pass some of the contamination to offspring during lactation[30]. Similarly to other species, studies have identified heavy metals in Atlantic white-sided dolphins including cadmium levels higher than in other dolphin species in southern latitudes.[33] The full effect of this contamination is currently unknown.

Conservation status

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The International Union of the Conservation of Nature (IUCN) currently classifies Atlantic white-sided dolphins as Least Concern.[1]

The North and Baltic Sea populations of the Atlantic white-sided dolphin are listed on Appendix II [34] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). They are listed on Appendix II[34] as they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[35] These species of dolphin are known to fall victims to in a polluted environment, a study from 1997 confirmed that the British and Irish populations of Atlantic white-sided dolphins to succumb to these effects.[7][36] [clarification needed]

In addition, the Atlantic white-sided dolphin is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS).[37]

See also

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References

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  1. ^ a b c Braulik, G. (2019). "Lagenorhynchus acutus". IUCN Red List of Threatened Species. 2019: e.T11141A50361160. doi:10.2305/IUCN.UK.2019-3.RLTS.T11141A50361160.en. Retrieved 17 June 2024.
  2. ^ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. ^ a b McGowen, Michael R; Tsagkogeorga, Georgia; Álvarez-Carretero, Sandra; dos Reis, Mario; Struebig, Monika; Deaville, Robert; Jepson, Paul D; Jarman, Simon; Polanowski, Andrea; Morin, Phillip A; Rossiter, Stephen J (21 October 2019). "Phylogenomic Resolution of the Cetacean Tree of Life Using Target Sequence Capture". Systematic Biology. 69 (3): 479–501. doi:10.1093/sysbio/syz068. ISSN 1063-5157. PMC 7164366. PMID 31633766.
  4. ^ a b c d e f g h i j k l m n o p q r s t u v w Reeves, Randall (2008). Guide to Marine Mammals of the World. New York: National Audubon Society. pp. 398–401. ISBN 978-0375411410.
  5. ^ a b Sergeant (1980). "Life history and northwest Atlantic status of the Atlantic white-sided dolphin, Lagenorhynchus acutus". Cetology. 37: 1–12.
  6. ^ a b c Neuenhagen (2007). "Histology and morphometrics of testes of the white-sided dolphin (Lagenorhynchus acutus) in bycatch samples from the Northeastern Atlantic". Mammalian Biology. 72 (5): 283–298. doi:10.1016/j.mambio.2006.10.008.
  7. ^ a b c Mckenzie, C.; Rogan, E.; Reid, R.; Wells, D. (1997). "Concentrations and patterns of organic contaminants in Atlantic white-sided dolphins (Lagenorhynchus acutus) from Irish and Scottish coastal waters". Environmental Pollution. 98 (1): 15–27. doi:10.1016/s0269-7491(97)00109-7. PMID 15093341.
  8. ^ a b Weinrich, Mason T.; Belt, Cynthia R.; Morin, David (April 2001). "Behavior and Ecology of the Atlantic White-Sided Dolphin (Lagenorhynchus acutus) in Coastal New England Waters". Marine Mammal Science. 17 (2): 231–248. doi:10.1111/j.1748-7692.2001.tb01268.x. ISSN 0824-0469.
  9. ^ Schevill, William E. (February 1956). "Lagenorhynchus acutus off Cape Cod". Journal of Mammalogy. 37 (1): 128–129. doi:10.2307/1375559. ISSN 0022-2372. JSTOR 1375559.
  10. ^ Powell, J.W.; Rotstein, D.S.; Mcfee, W.E. (2012). "First Records of the Melon-Headed Whale (Peponocephala electra) and the Atlantic White-Sided Dolphin (Lagenorhynchus acutus) in South Carolina". Southeastern Naturalist. 11 (1): 23–34. doi:10.1656/058.011.0102. S2CID 83544895.
  11. ^ a b Waring (2006). "U.S. Atlantic and Gulf of Mexico marine mammal stock assessments – 2005". NOAA Technical Memorandum NMFS-NE. 194: 346.
  12. ^ a b c d e Gaskin (1992). "Status of the Atlantic white-sided dolphin, Lagenorhynchus acutus, in Canada". Canadian Field-Naturalist. 106: 64–72.
  13. ^ Palka (1997). "Summary of knowledge of white-sided dolphins (Lagenorhynchus acutus) from US and Canadian Atlantic waters". Report of the International Whaling Commission. 47: 729–734.
  14. ^ Selzer (1988). "The distribution of white-sided (Lagenorhynchus acutus) and common dolphins (Delphinus delphis) vs. environmental features of the continental shelf of the northeastern United States". Marine Mammal Science. 4 (2): 141–153. doi:10.1111/j.1748-7692.1988.tb00194.x.
  15. ^ Doksæter (2008). "Distribution and feeding ecology of dolphins along the Mid-Atlantic ridge between Iceland and the Azores". Deep-Sea Research Part II: Topical Studies in Oceanography. 55 (1–2): 243–253. Bibcode:2008DSRII..55..243D. doi:10.1016/j.dsr2.2007.09.009.
  16. ^ a b Weinrich, M.T.; Belt, C.R.; Dorin, D. (2001). "Behavior And Ecology Of The Atlantic White-Sided Dolphin (Lagenorhynchus acutus) In Coastal New England Waters". Marine Mammal Science. 17 (2): 231–248. doi:10.1111/j.1748-7692.2001.tb01268.x.
  17. ^ a b c Reeves (1999). "Atlantic white-sided dolphin Lagenorhynchus acutus (Gray, 1828). In S. H. Ridgway and R. Harrison (eds.)". Handbook of Marine Mammals. 6: 31–56.
  18. ^ Mirimin (2011). "Insights into genetic diversity, parentage, and group composition of Atlantic white-sided dolphins (Lagenorhynchus acutus) off the West of Ireland based on nuclear and mitochondrial genetic markers". Journal of Heredity. 102 (1): 79–87. doi:10.1093/jhered/esq106. hdl:10379/12915. PMID 21059883.
  19. ^ Fernández (2016). "A genomewide catalogue of single nucleotide polymorphisms in white-beaked and Atlantic white-sided dolphins". Molecular Ecology Resources. 16 (1): 266–276. doi:10.1111/1755-0998.12427. PMID 25950249. S2CID 8129929.
  20. ^ a b c d Hamran (2014). "Distribution and vocal behavior of Atlantic white-sided dolphins (Lagenorhynchus acutus) in northern Norway". University of Nordland.
  21. ^ Baraff, L. S.; Asmutis-Silvia, R. A. (1998). "Long-Term Association of an Individual Long-Finned Pilot Whale and Atlantic White-Sided Dolphins". Marine Mammal Science. 14 (1): 155–161. doi:10.1111/j.1748-7692.1998.tb00700.x.
  22. ^ Larrat, S.; Measures, L.; Stephane, L. (2012). "Short Note Rake Marks on a Harbor Porpoise (Phocoena phocoena) Calf Suggestive of a Fatal Interaction with an Atlantic White-Sided Dolphin (Lagenorhynchus acutus)". Aquatic Mammals. 38 (1): 86–91. doi:10.1578/am.38.1.2012.86.
  23. ^ Ross, H.M.; Wilson, B. (1996). "Violent interactions between Bottlenose dolphins and Harbour porpoises". Proceedings of the Royal Society B: Biological Sciences. 263 (1368): 283–286. Bibcode:1996RSPSB.263..283R. doi:10.1098/rspb.1996.0043. S2CID 85372260.
  24. ^ Vollmer, Nicole L.; Ashe, Erin; Brownell, Robert L.; Cipriano, Frank; Mead, James G.; Reeves, Randall R.; Soldevilla, Melissa S.; Williams, Rob (2019). "Taxonomic revision of the dolphin genus Lagenorhynchus". Marine Mammal Science. 35 (3): 957–1057. doi:10.1111/mms.12573. ISSN 1748-7692. S2CID 92421374.
  25. ^ NOAA. "Atlantic White-Sided Dolphin". National Oceanic and Atmospheric Administration. U.S. Department of Commerce. Retrieved 25 November 2021.
  26. ^ a b Corcoran, Kieran (13 May 2019). "Eco-campaigners took these grisly photos of whale and dolphin hunts in the Faroe Islands". Insider Inc. Business Insider. Retrieved 25 November 2021.
  27. ^ a b Bloch, Dorete; Mikkelsen, Bjarni (26 February 2017). "Catch history and distribution of white- sided dolphin (Lagenorhynchus acutus) of the Faroe Islands / Veiðisøga og útbreiðsla av skjórutum springara (Lagenorhynchus acutus) í Føroyum". Fróðskaparrit - Faroese Scientific Journal. 57: 190–198. doi:10.18602/fsj.v57i0.82.
  28. ^ "Grindamenn: Drápið gekk ikki so illa".
  29. ^ Waring, Gordon. "Incidental Take of Marine Mammals in Foreign Fishery Activities Off the Northeast United States, 1977-88" (PDF). NOAA. Fishery Bulletin. Retrieved 16 March 2020.
  30. ^ Weisbrod (2001). "Species, tissue and gender-related organochlorine bioaccumulation in white-sided dolphins, pilot whales and their common prey in the northwest Atlantic". Marine Environmental Research. 51 (1): 29–50. Bibcode:2001MarER..51...29W. doi:10.1016/S0141-1136(00)00032-5. PMID 11125702.
  31. ^ Tuerk (2005). "Factors influencing persistent organic pollutant concentrations in the Atlantic white-sided dolphin (Lagenorhynchus acutus)". Environmental Toxicology and Chemistry. 24 (5): 1079–1087. doi:10.1897/04-120R.1. PMID 16110985. S2CID 23781649.
  32. ^ Montie (2009). "Organohalogen contaminants and metabolites in cerebrospinal fluid and cerebellum gray matter in short-beaked common dolphins and Atlantic white-sided dolphins from the western North Atlantic". Environmental Pollution. 157 (8–9): 2345–2358. doi:10.1016/j.envpol.2009.03.024. hdl:1912/2815. PMID 19375836.
  33. ^ Gallien (2001). "Cadmium-containing granules in kidney tissue of the Atlantic white-sided dolphin (Lagenorhyncus acutus) off the Faroe Islands" (PDF). Comparative Biochemistry and Physiology. 130 (3): 389–395. doi:10.1016/s1532-0456(01)00265-4. PMID 11701395. S2CID 20729337.
  34. ^ a b "Appendix II Archived 11 June 2011 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.
  35. ^ "Convention on Migratory Species page on the Atlantic white-sided dolphin". Archived from the original on 9 October 2011. Retrieved 31 August 2011.
  36. ^ Tuerk, K. J. S.; Kucklick, J. R.; McFee, W. E.; Pugh, R. S.; Becker, P. R. (2005). "Factors influencing persistent organic pollutant concentrations in the Atlantic white-sided dolphin (Lagenorhynchus acutus)†". Environmental Toxicology and Chemistry. 24 (5): 1079–1087. doi:10.1897/04-120r.1. PMID 16110985. S2CID 23781649.
  37. ^ Official website of the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas
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