Editing Blue whale (section)

==Conservation==
The global blue whale population is estimated to be 5,000–15,000 mature individuals and 10,000–25,000 total as of 2018. By comparison, there were at least 140,000 mature whales in 1926. There are an estimated total of 1,000–3,000 whales in the North Atlantic, 3,000–5,000 in the North Pacific, and 5,000–8,000 in the Antarctic. There are possibly 1,000–3,000 whales in the eastern South Pacific while the pygmy blue whale may number 2,000–5,000 individuals.<ref name="iucn"/> Blue whales have been protected in areas of the Southern Hemisphere since 1939. In 1955, they were given complete protection in the North Atlantic under the [[International Convention for the Regulation of Whaling]]; this protection was extended to the Antarctic in 1965 and the North Pacific in 1966.<ref name=Gambell_1979>{{cite journal | author1=Gambell, R. | title=The blue whale | journal=Biologist | volume=26 | pages=209–215 | date=1979}}</ref><ref name=Best_1993>{{cite journal | author1=Best, P. B. | title=Increase rates in severely depleted stocks of baleen whales | journal=ICES J. Mar. Sci. | volume=50 | issue=2 | pages=169–186 | date=1993| doi=10.1006/jmsc.1993.1018 | bibcode=1993ICJMS..50..169B }}</ref> The protected status of North Atlantic blue whales was not recognized by Iceland until 1960.<ref name="Sigurjónsson_1988">{{cite journal | author1=Sigurjónsson, J. | title=Operational factors of the Icelandic large whale fishery | journal=Reports of the International Whaling Commission| volume=38 | pages=327–333 | date=1988}}</ref> In the United States, the species is protected under the [[Endangered Species Act]].<ref name=NOAAblue/>

Blue whales are formally classified as [[Endangered species|endangered]] under both the U.S. [[Endangered Species Act]]<ref>{{cite web |url=https://ecos.fws.gov/docs/federal_register/fr21.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ecos.fws.gov/docs/federal_register/fr21.pdf |archive-date=9 October 2022 |url-status=live |title=Part 17 – Conservation of Endangered Species and Other Fish or Wildlife (First List of Endangered Foreign Fish and Wildlife as Appendix A) | date=2 June 1970 |publisher=[[U.S. Fish & Wildlife Service]] |access-date=24 December 2019}}</ref> and the [[IUCN Red List]].<ref name="iucn"/> They are also listed on Appendix&nbsp;I under the [[Convention on International Trade in Endangered Species of Wild Fauna and Flora]] (CITES)<ref>{{cite web | url=https://www.cites.org/eng/app/appendices.php | title=Appendices | date=26 November 2019 | publisher=Convention on International Trade in Endangered Species of Wild Fauna and Flora | access-date=24 December 2019}}</ref> and the [[Convention on the Conservation of Migratory Species of Wild Animals]].<ref>{{cite web | url=https://www.cms.int/sites/default/files/instrument/CMS-text.en_.PDF | title=Convention on the Conservation of Migratory Species of Wild Animals | date=23 June 1979 | publisher=[[United Nations Environment Programme]] | access-date=24 December 2019 | archive-url=https://web.archive.org/web/20200502225536/https://www.cms.int/sites/default/files/instrument/CMS-text.en_.PDF | archive-date=2 May 2020 | url-status=dead }}</ref> Although, for some populations, there is not enough information on current abundance trends (e.g., pygmy blue whales), others are [[critically endangered]] (e.g., Antarctic blue whales).<ref name=Samaran_etal_2013>{{cite journal | author1=Samaran, F. | author2=Stafford, K. M. | author3=Branch, T. A. | author4=Gedamke, J. | author5=Royer, Y.-J. | author6=Dziak, R. P. | author7=Guinet, C. | title=Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean | journal=PLOS ONE | volume=8 | issue=8 | page=e71561 | date=2013| bibcode=2013PLoSO...871561S | doi=10.1371/journal.pone.0071561 | pmid=23967221 | pmc=3742792 | doi-access=free }}</ref><ref>{{cite web | url=https://iucn-csg.org/35-updated-cetacean-red-list-assessments-published-in-nov-2018/ | title=Blue Whale | date=6 December 2018 | publisher=International Union for Conservation | access-date= 24 December 2019}}</ref>

===Threats===
[[File:FMIB 34640 Large Hump-Back -sic- Whale, 83 Feet Long.jpeg|thumb|Dead blue whale on [[flensing]] platform]]
In 2017, [[DNA]] evidence was used to identify whale bones at [[Iceland]]ic archaeological sites. Of the 124 bones analyzed more than 50% were from blue whales and some dated as far back as 900 CE. This, and other evidence, suggests that Icelanders were hunting whales as early as the 9th century, just as the [[settlement of Iceland]] began. Thus Icelanders would have been among the earliest known humans to hunt the blue whale.<ref>{{cite news |last1=Andrew |first1=Chapman |title=How Viking-Age Hunters Took Down the Biggest Animal on Earth |url=https://hakaimagazine.com/features/how-viking-age-hunters-took-down-the-biggest-animal-on-earth/ |access-date=7 May 2024 |work=Newsweek |date=28 February 2025}}</ref>

Blue whales were initially difficult to hunt because of their size and speed.<ref name=NOAA/> This began to change in the mid-19th century with the development of harpoons that can be shot as projectiles.<ref>{{cite book |author=Darby, Andrew |url=https://archive.org/details/harpoonintoheart00darb/page/38/mode/2up |title=Harpoon Into the Heart of Whaling |publisher=Hachette Books |year=2009 |isbn=9780786732005 |pages=38–39 |url-access=registration}}</ref> Blue whale whaling peaked between 1930 and 1931 with 30,000 animals taken. Harvesting of the species was particularly high in the Antarctic, with 350,000–360,000 whales taken in the first half of the 20th century. In addition, 11,000 North Atlantic whales (mostly around Iceland) and 9,500 North Pacific whales were killed during the same period.<ref name=Sears_Perrin_2018/> The International Whaling Commission banned all hunting of blue whales in 1966 and gave them worldwide protection.<ref>{{cite web|title=Blue whale – ''Balaenoptera musculus''|publisher=International Whaling Commission|access-date=25 February 2022|url=https://iwc.int/blue-whale}}</ref> However, the [[Soviet Union]] continued to illegally hunt blue whales and other species up until the 1970s.<ref>{{cite journal|author1=Ivashchenko, Y.|author2=Clapham, P. J.|author3=Brownell, R.|year=2011|title=Soviet Illegal Whaling: The Devil and the Details|journal=Marine Fisheries Review|volume=73|issue=1|pages=1–19|url=https://aquadocs.org/bitstream/handle/1834/26267/mfr7331.pdf?sequence=1&isAllowed=y|access-date=26 January 2023|archive-date=22 March 2022|archive-url=https://web.archive.org/web/20220322075344/https://aquadocs.org/bitstream/handle/1834/26267/mfr7331.pdf?sequence=1&isAllowed=y}}</ref>
[[File:Blue whale ship strike death.jpg|thumb|right|Researchers examine a dead blue whale killed by collision with a ship]]
[[Environmental impact of shipping#Wildlife collisions|Ship strikes]] are a significant mortality factor for blue whales, especially off the [[U.S. West Coast]].<ref name="Berman-Kowalewski_etal_2010">{{cite journal | author1=Berman-Kowalewski, M. | author2=Gulland, F. | author3=Wilkin, S. | author4=Calambokidis, J. | author5=Mate, B. | author6=Cordaro, J. | author7=Rotstein, D. | author8=St. Leger, J. | author9=Collins, P. | author10=Fahy, K. | author11=Dover, S. | s2cid=86304413 | title=Association between blue whale mortality and ship strikes along the California coast | journal=Aquatic Mammals | volume=36 | issue=1 | pages=59–66 | date=2010| doi=10.1578/AM.36.1.2010.59 }}</ref> A total of 17 blue whales were killed or suspected to have been killed by ships between 1998 and 2019 off the U.S. West Coast.<ref name="NOAA" /> Five deaths in 2007 off California were considered an unusual mortality event, as defined under the [[Marine Mammal Protection Act]].<ref name=Berman-Kowalewski_etal_2010/><ref name=Abramson_etal_2009>{{cite report | author1=Abramson, L. | author2=Polefka, S. | author3=Hastings, S. | author4=Bor, K. | title=Reducing the Threat of Ship Strikes on Large Cetaceans in the Santa Barbara Channel Region and Channel Islands National Marine Sanctuary: Recommendations and Case Studies | publisher=Channel Islands National Marine Sanctuary Advisory Council | pages=1–73 | date=2009}}</ref> Lethal ship strikes are also a problem in Sri Lankan waters, where their habitat intersects with one of the world's most active shipping routes.<ref name=deVos_etal_2016>{{cite journal | author1=de Vos, A. | author2=Brownell, R. L. Jr. | author3=Tershy, B. R. | author4=Croll, D. A. | title=Anthropogenic threats and conservation needs of blue whales, "Balaenoptera musculus indica", around Sri Lanka | journal=J. Mar. Biol. | volume=2016 | issue=8420846 | pages=1–12 | date=2016| doi=10.1155/2016/8420846 | doi-access=free }}</ref> Here, strikes caused the deaths of eleven blue whales in 2010 and 2012,<ref name=Priyadarshana_etal_2015>{{cite report | author1=Priyadarshana, T. | author2=Randage, R. | author3=Alling, A. | author4=Calderan, S. | author5=Gordon, J. | author6=Leaper, R. | author7=Porter, L. | title=An update on work related to ship strike risk to Blue whales off southern Sri Lanka | publisher=The International Whaling Commission | volume=SC66A | date=2015}}</ref> and at least two in 2014.<ref name=Randage_etal_2014>{{cite journal | author1=Randage, S. M. | author2=Alling, A. | author3=Currier, K. | author4=Heywood, E. | title=Review of the Sri Lanka blue whale (''Balaenoptera musculus'') with observations on its distribution in the shipping lane | journal=Journal of Cetacean Research and Management | year=2023 | volume=14 | pages=43–49 | doi=10.47536/jcrm.v14i1.522 | s2cid=46399716 | doi-access=free }}</ref> Ship-strike mortality claimed the lives of two blue whales off southern Chile in the 2010s.<ref name=Brownell_etal_2014>{{cite report | author1=Brownell, R. L. Jr. | author2=Cabrera, E. | author3=Galletti-Vernazzani, B. | title=Dead blue whale in Puerto Montt, Chile: Another case of ship collision mortality | publisher=International Whaling Commission | volume=SC/65b/HIM08 | date=2014}}</ref><ref name=IWC_2017>{{cite report | author1=International whaling Commission | title=Report of the Scientific Committee | publisher=International Whaling Commission | page=136 | date=2017}}</ref> Possible measures for reducing future ship strikes include better predictive models of whale distribution, changes in shipping lanes, vessel speed reductions, and seasonal and dynamic management of shipping lanes.<ref name=Redfern_etal_2013>{{cite journal | author1=Redfern, J. V. | author2=McKenna, M. F. | author3=Moore, T. J. | author4=Calambokidis, J. | author5=Deangelis, M. L. | author6=Becker, E. A. | author7=Barlow, J. | author8=Forney, K. A. | author9=Fiedler, P. C. | author10=Chivers, S. J. | title=Assessing the risk of ships striking large whales in marine spatial planning | journal=[[Conservation Biology (journal)|Conservation Biology]] | volume=22 | issue=2 | pages=292–302 | date=2013| doi=10.1111/cobi.12029 | pmid=23521668 | bibcode=2013ConBi..27..292R | s2cid=17833403 }}</ref><ref name=Dransfield_etal_2014>{{cite journal | author1=Dransfield, A. | author2=Hines, E. | author3=McGowan, J. | author4=Holzman, B. | author5=Nur, N. | author6=Elliott, M. | author7=Howar, J. | author8=Jacncke, J. | title=Where the whales are: using habitat modeling to support changes in shipping regulations within National Marine Sanctuaries in Central California | journal=Endanger Species Res | volume=26 | issue=1 | pages=39–57 | date=2014| doi=10.3354/esr00627 | doi-access=free }}</ref> Few cases of blue whale entanglement in commercial fishing gear have been documented. The first report in the U.S. occurred off California in 2015, reportedly some type of deep-water trap/pot fishery.<ref name=Carretta_etal_2017>{{cite report | author1=Carretta, J. V. | author2=Muto, M. M. | author3=Greenman, J. | author4=Wilkinson, K. | author5=Viezbicke, J. | author6=Jannot, J. | title=Sources of human-related injury and mortality for U.S. Pacific west coast marine mammal stock assessments, 2011– 2015 | publisher=NOAA | volume=PSRG-2017-07 | date=2017}}</ref> Three more entanglement cases were reported in 2016.<ref name=NMFS_2017>{{cite report | author1=NMFS | title=National Report on Large Whale Entanglements | publisher=NOAA | url=https://www.fisheries.noaa.gov/resource/document/national-report-large-whale-entanglements-2017 | date=2017}}</ref> In Sri Lanka, a blue whale was documented with a net wrapped through its mouth, along the sides of its body, and wound around its tail.<ref name=deVos_2015>{{cite book | author1=de Vos, A. | title=Deepwater Horizon oil spill: Final Programmatic Damage Assessment and Restoration Plan and Final Programmatic Environmental Impact Statement | chapter=Marine life on the line | editor1-last=Braun | editor1-first=D. | publisher=National Geographic | page=685 | chapter-url=http://www.gulfspillrestoration.noaa.gov/restoration-planning/gulf-plan | date=2015}}</ref>

Increasing [[Anthropogenic hazard|man-made]] underwater noise impacts blue whales.<ref name=Southall_etal_2018>{{cite journal | author1=Southall, B. L. | author2=Hatch, L. | author3=Scholik-Schlomer, A. | author4=Bergmann, T. | author5=Jasny, M. | author6=Metcalf, K. | author7=Weilgart, L. | author8=Wright, A. J. | author9=Perera, M. E. | title=Reducing noise from large commercial ships: progress and partnerships | journal=Proc. Mar. Saf. Sec. Council | volume=1 | pages=58–65 | date=2018}}</ref><ref name=Wiggins_etal_2001>{{cite journal | author1=Wiggins, S. M. | author2=Oleson, E. M. | author3=Hildebrand, J. A. | title=Blue whale call intensity varies with ambient noise level | journal=[[Journal of the Acoustical Society of America]] | volume=110 | issue=5 | page=2771 | date=2001| bibcode=2001ASAJ..110.2771W | doi=10.1121/1.4777708 }}</ref> They may be exposed to noise from commercial shipping<ref name=McKenna_etal_2012>{{cite journal | author1=McKenna, M. F. | author2=Ross, D. | author3=Wiggins, S. M. | author4=Hildebrand, J. A. | s2cid=9474116 | title=Underwater radiated noise from modern commercial ships | journal=The Journal of the Acoustical Society of America | volume=131 | issue=1 | pages=92–103 | date=2012| doi=10.1121/1.3664100 | pmid=22280574 | bibcode=2012ASAJ..131...92M }}</ref><ref name=Szesciorka_etal_2019>{{cite journal | author1=Szesciorka, A. R. | author2=Allen, A. N. | author3=Calambokidis, J. | author4=Fahlbusch, J. | author5=McKenna, M. F. | author6=Southall, B. L. | title=A case study of a near vessel strike of a blue whale: perceptual cues and fine-scale aspects of behavioral avoidance | journal=Front. Mar. Sci. | volume=6 | issue=761 | pages=1–10 | date=2019| doi=10.3389/fmars.2019.00761 | doi-access=free }}</ref> and seismic surveys as a part of oil and gas exploration.<ref name=DiIorio_Ckark_2009>{{cite journal | author1=Di Iorio, L. | author2=Clark, C. W. | title=Exposure to seismic survey alters blue whale acoustic communication | journal=Biology Letters | volume=6 | issue=1 | pages=1–4 | date=2009}}</ref><ref name=McDonald_etal_1995>{{cite journal | author1=McDonald, M. A. | author2=Hildebrand, J. A. | author3=Webb, S. C. | s2cid=3829165 | title=Blue and fin whales observed on a seafloor array in the Northeast Pacific | journal=Journal of the Acoustical Society of America | volume=98 | issue=2 | pages=712–721 | date=1995| doi=10.1121/1.413565 | pmid=7642810 | bibcode=1995ASAJ...98..712M | url=https://escholarship.org/uc/item/2sx2b1cj }}</ref> Blue whales in the [[Southern California Bight]] decreased calling in the presence of mid-frequency active (MFA) [[sonar]].<ref name="Melcón_etal_2012">{{cite journal | author1=Melcón, M. L. | author2=Cummins, A. J. | author3=Kerosky, S. M. | author4=Roche, L. K. | author5=Wiggins, S. M. | author6=Hildebrand, J. A. | title=Blue Whales Respond to Anthropogenic Noise | journal=PLOS ONE | volume=7 | issue=2 | page=e32681 | date=2012| doi=10.1371/journal.pone.0032681 | pmid=22393434 | pmc=3290562 | bibcode=2012PLoSO...732681M | doi-access=free }}</ref> Exposure to simulated MFA sonar was found to interrupt blue whale deep-dive feeding, but no changes in behavior were observed in individuals feeding at shallower depths. The responses also depended on the animal's behavioral state, its (horizontal) distance from the sound source and the availability of prey.<ref name=Southall_etal_2019>{{cite journal | author1=Southall, B. L. | author2=DeRuiter, S. L. | author3=Friedlaender, A. | author4=Stimpert, A. K. | author5=Goldbogen, J. A. | author6=Hazen, E. | author7=Casey, C. | author8=Fregosi, S. | author9=Cade, D. E. | author10=Allen, A. N. | author11=Harris, C. M. | author12=Schorr, G. | author13=Moretti, D. | title=Behavioral responses of individual blue whales (''Balaenoptera musculus'') to mid-frequency military sonar | journal=[[The Journal of Experimental Biology]]| volume=222 | issue=jeb190637 | pages=jeb190637 | date=2019| doi=10.1242/jeb.190637 | pmid=30833464 | doi-access=free | bibcode=2019JExpB.222B0637S | hdl=10023/19592 | hdl-access=free }}</ref>

The potential impacts of [[pollutants]] on blue whales is unknown. However, because blue whales feed low on the [[food chain]], there is a lesser chance for [[bioaccumulation]] of organic chemical contaminants.<ref name=OShea_Brownell_1994>{{cite journal | author1=O'Shea, T. J. | author2=Brownell, R. L. | title=Organochlorine and metal contaminants in baleen whales:a review and evaluation of conservation implications | journal=[[Science of the Total Environment]]| volume=154 | issue=2–3 | pages=179–200 | date=1994| doi=10.1016/0048-9697(94)90087-6 | pmid=7973606 | bibcode=1994ScTEn.154..179O }}</ref> Analysis of the earwax of a male blue whale killed by a collision with a ship off the coast of California showed contaminants like pesticides, flame retardants, and mercury. Reconstructed [[persistent organic pollutant]] (POP) profiles suggested that a substantial [[Maternal transfer in aquatic mammals|maternal transfer]] occurred during gestation and/or lactation.<ref name=Trumble_etal_2013>{{cite journal | author1=Trumble, S. J. | author2=Robinson, E. M. | author3=Berman-Kowalewski, M. | author4=Potter, C. W. | author5=Usenko, S. | title=Blue whale earplug reveals lifetime contaminant exposure and hormone profiles | journal=Proceedings of the National Academy of Sciences | volume=110 | issue=42 | pages=16922–16926 | date=2013| doi=10.1073/pnas.1311418110 | bibcode=2013PNAS..11016922T | doi-access=free | pmid=24043814 | pmc=3801066 }}</ref> Male blue whales in the [[Gulf of St. Lawrence]], Canada, were found to have higher concentrations of PCBs, [[dichlorodiphenyltrichloroethane]] (DDT), [[metabolites]], and several other organochlorine compounds relative to females, reflecting maternal transfer of these persistent contaminants from females into young.<ref name=Metcalfe_etal_2004>{{cite journal | author1=Metcalfe, C. D. | author2=Koenig, B. G. | author3=Metcalfe, T. L. | author4=Paterson, G. | author5=Sears, R. | title=Intra- and inter-species differences in persistent organic contaminants in the blubber of blue whales and humpback whales from the Gulf of St. Lawrence, Canada | journal=Marine Environmental Research| volume=57 | issue=4 | pages=245–260 | date=2004| doi=10.1016/j.marenvres.2003.08.003 | pmid=14749058 | bibcode=2004MarER..57..245M }}</ref>