Editing Blue whale (section)

===Subspecies and stocks===
At least four subspecies of blue whale are traditionally recognized, some of which are divided into population stocks or "management units".<ref name=NOAA>{{cite report|first1=Chris W. |last1= Oliver|date=November 2020|title= Recovery Plan for the Blue Whale (''Balaenoptera musculus'') |publisher=National Oceanic and Atmospheric Administration |url=https://www.fisheries.noaa.gov/resource/document/recovery-plan-blue-whale-balaenoptera-musculus-0|access-date=12 April 2022}}</ref><ref name=SMM_2016>{{cite web|url=https://www.marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/ |title=List of Marine Mammal Species and Subspecies |date=13 November 2016 | publisher=[[The Society for Marine Mammalogy]] |access-date=30 December 2019}}</ref> They have a worldwide distribution, but are mostly absent from the [[Arctic Ocean]] and the [[Mediterranean]], [[Sea of Okhotsk|Okhotsk]], and [[Bering Sea]].<ref name=NOAA/>
[[File:Blue Whale 001 body bw.jpg|thumb|right|alt=Aerial photograph of an adult blue whale showing its length |Aerial view of adult blue whale]]
*Northern subspecies (''B. m. musculus'')
**North Atlantic population – This population is mainly documented from [[New England]] along eastern Canada to Greenland, particularly in the [[Gulf of St. Lawrence]], during summer though some individuals may remain there all year. They also aggregate near Iceland and have increased their presence in the [[Norwegian Sea]]. They are reported to migrate south to the [[West Indies]], the [[Azores]] and northwest Africa.<ref name=NOAA/> 
**Eastern North Pacific population – Whales in this region mostly feed off California's coast from summer to fall and then Oregon, Washington State, the [[Alaska Current|Alaska Gyre]] and [[Aleutian Islands]] later in the fall. During winter and spring, blue whales migrate south to the waters of Mexico, mostly the [[Gulf of California]], and the [[Costa Rica Thermal Dome|Costa Rica Dome]], where they both feed and breed.<ref name=NOAA/>
**Central/Western Pacific population – This stock is documented around the [[Kamchatka Peninsula]] during the summer; some individuals may remain there year-round. They have been recorded wintering in Hawaiian waters, though some can be found in the [[Gulf of Alaska]] during fall and early winter.<ref name=NOAA/>
*Northern Indian Ocean subspecies (''B. m. indica'') – This subspecies can be found year-round in the northwestern Indian Ocean, though some individuals have recorded travelling to the [[Crozet Islands]] during between summer and fall.<ref name=NOAA/>
*Pygmy blue whale (''B. m. brevicauda'')
**Madagascar population – This population migrates between the [[Seychelles]] and [[Amirante Islands]] in the north and the [[Crozet Island]]s and [[Prince Edward Islands]] in the south were they feed, passing through the [[Mozambique Channel]].<ref name=NOAA/> 
**Australia/Indonesia population – Whales in this region appear to winter off Indonesia and migrate to their summer feeding grounds off the coast of Western Australia, with major concentrations at [[Perth Canyon]] and an area stretching from the [[Great Australian Bight]] and [[Bass Strait]].<ref name=NOAA/>
**Eastern Australia/New Zealand population – This stock may reside in the [[Tasman Sea]] and the [[Lau Basin]] in winter and feed mostly in the [[South Taranaki Bight]] and off the coast of eastern [[North Island]]. Blue whales have been detected around New Zealand throughout the year.<ref name=NOAA/>
*Antarctic subspecies (''B. m. intermedia'') – This subspecies includes all populations found around the Antarctic. They have been recorded to travel as far north as eastern tropical Pacific, the central Indian Ocean, and the waters of southwestern Australia and northern New Zealand.<ref name=NOAA/>

Blue whales off the [[Chile]]an coast might be a separate subspecies based on their geographic separation, genetics, and unique song types.<ref name=LeDuc_etal_2007>{{cite journal | author1=LeDuc, R. G. | author2=Dizon, A. E. | author3=Goto, M. | author4=Pastene, L. A. | author5=Kato, H. | author6=Nishiwaki, S. | author7=LeDuc, C. A. | author8=Brownell, R. L. | title=Patterns of genetic variation in Southern Hemisphere blue whales, and the use of assignment test to detect mixing on the feeding grounds | journal=Journal of Cetacean Research and Management | volume=9 | pages=73–80 | date=2023| doi=10.47536/jcrm.v9i1.694 | s2cid=257136658 | doi-access=free }}</ref><ref name=Torres-Florez_etal_2015>{{cite journal | author1=Torres-Florez, J. P. | author2=Olson, P. A. | author3=Bedrinana-Romano, L. | author4=Rosenbaum, H. | author5=Ruiz, J. | author6=Leduc, R. | author7=Huck-Gaete, R. | title=First documented migratory destination for eastern South Pacific blue whales | journal=Marine Mammal Science | volume=31 | issue=4 | pages=1580–1586 | date=2015| doi=10.1111/mms.12239 | doi-access=free | bibcode=2015MMamS..31.1580T }}</ref><ref name=Buchan_etal_2010>{{cite journal | author1=Buchan, S. J. | author2=Rendell, L. E. | author3=Hucke-Gaete, R. | title=Preliminary recordings of blue whale (''Balaenoptera musculus'') vocalizations in the Gulf of Corcovado, northern Patagonia Chile | journal=Marine Mammal Science | volume=26 | issue=2 | pages=451–459 | date=2010| doi=10.1111/j.1748-7692.2009.00338.x | bibcode=2010MMamS..26..451B }}</ref> Chilean blue whales might overlap in the [[Eastern Tropical Pacific]] with [[Antarctica]] blue whales and Eastern North Pacific blue whales. Chilean blue whales are genetically differentiated from Antarctica blue whales such that [[interbreeding]] is unlikely. However, the genetic distinction is less between them and the Eastern North Pacific blue whale, hence there might be gene flow between the Southern and Northern Hemispheres.<ref name=LeDuc_etal_2016>{{cite journal | author1=LeDuc, R. G. | author2=Archer, E. I. | author3=Lang, A. R. | author4=Martien, K. K. | author5=Hancock-Hanser, B. | author6=Torres-Florez, J. P. | author7=Hucke-Gaete, R. | author8=Rosenbaum, H. R. | author9=Van Waerebeek, K. | author10=Brownell, R. L. Jr. | author11=Taylor, B. L. | title=Genetic variation in blue whales in the eastern Pacific: implication for taxonomy and use of common wintering grounds | journal=[[Molecular Ecology]] | volume=26 | issue=3 | pages=740–751 | date=2016| doi=10.1111/mec.13940 | pmid=27891694 | s2cid=206184206 }}</ref> A 2019 study by Luis Pastene, Jorge Acevedo and Trevor Branch provided new morphometric data from a survey of 60 Chilean blue whales, hoping to address the debate about the possible distinction of this population from others in the Southern Hemisphere. Data from this study, based on whales collected in the [[Whaling in Chile|1965/1966 whaling season]], shows that both the maximum and mean body length of Chilean blue whales lies between these values in pygmy and Antarctic blue whales. Data also indicates a potential difference in snout-eye measurements between the three, and a significant difference in fluke-anus length between the Chilean population and pygmy blue whales. This further confirms Chilean blue whales as a separate population, and implies that they do not fall under the same subspecies as the pygmy blue whale (''B. m. brevicauda'').<ref name=Pastene_etal_2019>{{Cite journal |last1=Pastene |first1=Luis A. |last2=Acevedo |first2=Jorge |last3=Branch |first3=Trevor A. |date=2019 |title=Morphometric analysis of Chilean blue whales and implications for their taxonomy |url=https://onlinelibrary.wiley.com/doi/10.1111/mms.12625 |journal=Marine Mammal Science |language=en |volume=36 |issue=1 |pages=116–135 |doi=10.1111/mms.12625 |issn=0824-0469}}</ref>

A 2024 genomic study of the global blue whale population found support for the subspecific status of Antarctic and Indo-western Pacific blue whales but not eastern Pacific blue whales. The study found "...divergence between the eastern North and eastern South Pacific, and among the eastern Indian Ocean, the western South Pacific and the northern Indian Ocean." and "no divergence within the Antarctic".<ref>{{cite journal|author1=Attard, C. R. M.|author2=Sandoval-Castillo, J|author3=Lang, A. R.|author4=Vernazzani, B. G.|author5=Torres, L. G.|author6=Baldwin, R|author7=Jenner, K. C. S.|author8=Gill, P. C.|author9=Burton, C. L. K.|author10=Barceló, A|author11=Sironi, M|author12=Jenner, M.-N. M.|author13=Morrice, M. G.|author14=Beheregaray, L. B.|author15=Möller, L. M.|year=2024|title=Global conservation genomics of blue whales calls into question subspecies taxonomy and refines knowledge of population structure|journal=Animal Conservation|volume=27|issue=5|pages=626–638|doi=10.1111/acv.12935|bibcode=2024AnCon..27..626A |doi-access=free}}</ref>