Sei whale: Difference between revisions

{{Short description|LargeThird-largest species of baleen whale}}

The '''sei whale''' ({{IPAc-en|s|eɪ}} {{respell|SAY}},<ref>{{OED|sei whale}}</ref> {{IPA-no|sæɪ|lang}}; '''''Balaenoptera borealis''''') is a [[baleen whale]]. It is one of ten [[rorqual]] species, and the third-largest member after the [[blue whale|blue]] and [[fin whale]]s. TheyIt can grow up to {{cvt|19.5|m}} in length and weigh as much as {{cvt|28|t}}. Two subspecies are recognized: ''B. b. borealis'' and ''B. b. schlegelii''. The whale's [[Anatomical terms of location#Dorsal and ventral|ventral]] surface has sporadic markings ranging from light grey to white, and its body is usually dark steel grey in colorcolour. It is among the fastest of all [[cetaceans]], and can reach speeds of up to {{cvt|50|km/h}} over short distances. 

It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids  [[polar water|polar]] and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool, subpolar waters in summer to [[temperate]], subtropical waters in winter with a lifespan of 70 years. It is a [[filter feeder]], with its diet consisting primarily of [[copepods]], [[krill]], and other [[zooplankton]]. It is typically solitary or can be found in groups numbering half a dozen. During the breeding period, a mating pair will remain together. Sei whale vocalizations usually lasts half a second, and occurs at 240–625 hertz.

=== EtymologyDescription ===

The sei whale is the third-largest balaenopterid, after the [[blue whale]] and the [[fin whale]].<ref name="av">{{cite journal | author = S.L. Perry | author2 = D.P. DeMaster | author3 = G.K. Silber | year = 1999 | title = Special Issue: The Great Whales: History and Status of Six Species Listed as Endangered Under the U.S. Endangered Species Act of 1973 | journal = Marine Fisheries Review | volume = 61 | issue = 1 | url = http://spo.nwr.noaa.gov/mfr611/mfr611.htm | pages = 52–58 | access-date = 26 April 2011 | archive-url = https://web.archive.org/web/20110721055959/http://spo.nwr.noaa.gov/mfr611/mfr611.htm | archive-date = 21 July 2011 | url-status = dead | df = dmy-all }}</ref> Adults usually weigh between {{cvt|15|-|20|MT}}.<ref name="Lockyer1976" /> FemalesThey areexhibit considerably[[sexual largerdimorphism]], with females outweighing and being longer than malestheir male counterparts.<ref name="nmfs">{{cite book | author = Reeves, R. | author2 = G. Silber | author3 = M. Payne | title = Draft Recovery Plan for the Fin Whale ''Balaenoptera physalus'' and Sei Whale ''Balaenoptera borealis'' | publisher = National Marine Fisheries Service | date = July 1998 | location = Silver Spring, Maryland | url = http://www.cresli.org/cresli/pdf%20documents/finwhale.pdf | access-date = 5 November 2006 | archive-url = https://web.archive.org/web/20160303204014/http://www.cresli.org/cresli/pdf%20documents/finwhale.pdf | archive-date = 3 March 2016 | url-status = dead }}</ref> At birth, a calf typically measures {{cvt|4.4|-|4.5|m}} in length.<ref>{{Cite book |last= |first= |url=https://books.google.com/books?id=gfopb_WsW4YC&dq=info:f3100ZalxFIJ:scholar.google.com/&pg=RA3-PA25 |title=Marine Fisheries Review |date=1984 |publisher=NMFS, Scientific Publications Office |pages=27 |language=en}}</ref>

The sei whale is among the fastest [[cetacea]]ns. The American [[naturalist]] [[Roy Chapman Andrews]] compared the sei whale to the [[cheetah]], because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".<ref>Andrews, Roy Chapman. 1916. ''Whale hunting with gun and camera; a naturalist's account of the modern shore-whaling industry, of whales and their habits, and of hunting experiences in various parts of the world''. New York: D. Appleton and Co., p. 128.</ref> It can reach speeds of up to {{cvt|50|km/h}} over short distances.<ref name="adw" /> However, it is not a remarkable diver, reaching relatively shallow depths for 5 to 15 minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 60 seconds (range: 45–90 sec.). UnlikeWhen theabout finto whaledive, the sei whale tendsusually notjust tosinks risebelow highthe outsurface; ofonly the waterdorsal asfin it dives, usually just sinking below the surface. Theand [[Blowhole (biology)|blowholes]] and dorsal fin are often exposed above the water surface almost simultaneouslyprotrude. The whale almost never lifts its flukes above the surface, and is generally less [[WhaleCetacean surfacing behaviour|active on water surfaces]] than theother closelywhale related Bryde's whalespecies; itthey rarely exhibit [[Whale#Behavior|breacheslobtail]] behaviour.<ref name="nmfs" />

The sei whale makes long, loud, low-frequency sounds. Relatively little is known about specific calls, but in 2003, observers noted sei whale calls in addition to sounds that could be described as "growls" or "whooshes" off the coast of the [[Antarctic Peninsula]].<ref name="mcdonald05">{{cite journal | author = McDonald, M. |author2=Hildebrand, J. |author3=Wiggins, S. |author4=Thiele, D. |author5=Glasgow, D. |author6=Moore, S. | title = Sei whale sounds recorded in the Antarctic | journal = The Journal of the Acoustical Society of America |date=December 2005 | volume = 118 | issue = 6 | pmid = 16419837 | pages = 3941–3945 | url = https://escholarship.org/content/qt6z22w129/qt6z22w129.pdf?t=lnrzou | doi = 10.1121/1.2130944|bibcode=2005ASAJ..118.3941M |s2cid=2094987 }}</ref> Many calls consisted of multiple parts at different frequencies. This combination distinguishes their calls from those of other whales. Most calls lastedlast about a half second, and occurredoccur in the 240–62537–98 [[hertz]] range, well within the range of human hearing. The maximum volume of the vocal sequences is reported as 156 [[decibel]]s relative to 1 [[Pascal (unit)|micropascal (μPa)]] at a reference distance of one metre.<ref name="mcdonald05" /> An observer situated one metre from a vocalizing whale would perceive a volume roughly equivalent to the volume of a jackhammer operating two meters away.<ref>Direct comparisons of sounds in water to sounds in air can be complicated, see [http://www.surtass-lfa-eis.com/Terms/index.htm this description] {{webarchiveusurped|url1=[https://web.archive.org/web/20090725234254/http://www.surtass-lfa-eis.com/Terms/index.htm |date=25 July 2009this description]}} for more information.</ref>

In the North Atlantic, its range extends from [[southern Europe]] or [[Northwest Africa|northwestern Africa]] to Norway, and from the [[southern United States]] to [[Greenland]].<ref name="Gambell85a">{{cite book | author = Gambell, R. | year = 1985 | chapter = Sei Whale ''Balaenoptera borealis'' Lesson, 1828 | title = Handbook of Marine Mammals, Vol. 3 | editor = S.H. Ridgway | editor2 = R. Harrison | publisher = Academic Press | location = London | pages = 155–170 }}</ref> The southernmost confirmed records are strandings along the northern [[Gulf of Mexico]] and in the [[Greater Antilles]].<ref name="mead" /> ThroughoutIt itsrarely range, the whale tends not to frequent semienclosed bodies of water, such as the Gulf of Mexico,enters the [[Gulf of Saint Lawrence]], [[Hudson Bay]], the [[NorthMediterranean Sea]], and the [[Mediterranean Sea]].<ref name="nmfs" /> It occurs predominantly in deep water, occurring most commonly over the [[continental shelf|continental slope]],<ref name="CETAP">{{cite report | author = CETAP | year = 1982 | title = Final ReportGulf of the Cetacean and Turtle Assessment ProgramMexico, Universitywhich ofare Rhodeboth Island,considered to Bureaube ofsmall Landwaterbodies. ManagementSei |whales publisherare =pelagic U.S.and Departmentare oftypically the Interior. Ref. No. AA551-CT8–48}}</ref>found in basins situated between banks,<ref name="sutcliffe">{{cite book | author1= Sutcliffe, W.H. Jr. |author2=P.F. Brodie | year = 1977 | chapter = Whale distributions in Nova Scotia waters | title = Fisheries & Marine Service Technical Report No. 722 }}</ref>oceans or [[submarine canyon]]open areasseas.<ref name="kenney87nmfs">{{cite journal | author1= Kenney, R.D. |author2=H.E. Winn | year = 1987 | title = Cetacean biomass densities near submarine canyons compared to adjacent shelf/slope> areas | journal = Cont. Shelf Res. | volume = 7 | pages = 107–114 | doi = 10.1016/0278-4343(87)90073-2 | issue=2|bibcode=1987CSR.....7..107K }}</ref>

Sei whales have been recorded from northern Indian Ocean as well such as around [[Sri Lanka]] and [[India]]n coasts.<ref>Sathasivam K.. 2015. [https://www.cbd.int/doc/meetings/mar/ebsaws-2015-01/other/ebsaws-2015-01-gobi-submission5-en.pdf A CATALOGUE OF INDIAN MARINE MAMMAL RECORDS] (pdf)</ref> In the Southern Hemisphere, summer distribution based upon historic catch data is between [[40th parallel south|40°S]] and [[50th parallel south|50°S]] latitude in the South Atlantic and southern Indian Oceans and [[45th parallel south|45°S]] and [[60th parallel south|60°S]] in the South Pacific, while winter distribution is poorly known, with former winter whaling grounds being located off northeastern Brazil ([[7th parallel south|7°S]]) and Peru ([[6th parallel south|6°S]]).<ref name="iucn" /> The majority of the "sei" whales caught off Angola and Congo, as well as other nearby areas in equatorial West Africa, are thought to have been predominantly misidentified [[Bryde's whale]]s. For example, Ruud (1952) found that 42 of the "sei whale" caught off [[Gabon]] in 1952 were actually Bryde's whales, based on examination of their baleen plates. The only confirmed historical record is the capture of a {{convert|14|m|ft|abbr=on}} female, which was brought to the Cap Lopez whaling station in Gabon in September 1950. During cetacean sighting surveys off Angola between 2003 and 2006, only a single confirmed sighting of two individuals was made in August 2004, compared to 19 sightings of Bryde's whales.<ref>{{cite journal| last1 = Weir | first1 = C.R. | year = 2010 | title = A review of cetacean occurrence in West African waters from the Gulf of Guinea to Angola | journal = Mammal Review | volume = 40 | pages = 2–39 | doi=10.1111/j.1365-2907.2009.00153.x}}</ref> Sei whales are commonly distributed along west to southern Latin America, including the entire Chilean coast down to the [[Beagle Channel]].<ref>Daniel.Bisson – [https://www.panoramio.com/photo/71888436 SEI Whale at Beagle canal, Ushuaia, Argentina] {{webarchive|url=https://web.archive.org/web/20160413175552/http://www.panoramio.com/photo/71888436 |date=13 April 2016 }}</ref><ref>OceanSounds e.V. - [http://ocean-sounds.org/en_US/whales-in-patagonia/marine-mammals-in-patagonia/sei-whale/ Sei whale] {{Webarchive|url=https://web.archive.org/web/20160413012011/http://ocean-sounds.org/en_US/whales-in-patagonia/marine-mammals-in-patagonia/sei-whale/ |date=13 April 2016 }}</ref> The Falkland Islands appear to be a regionally important area for the sei whale, as a small population exists in coastal waters off the eastern Falkland or Malvinas archipelago. For reasons unknown, the whales prefer to stay inland here, even venturing into large bays.<ref>{{Cite journal |last1=Baines |first1=Mick |last2=Weir |first2=Caroline R. |date=2020-12-23 |title=Predicting suitable coastal habitat for sei whales, southern right whales and dolphins around the Falkland or Malvinas Islands |journal=PLOS ONE |language=en |volume=15 |issue=12 |pages=e0244068 |doi=10.1371/journal.pone.0244068 |doi-access=free |issn=1932-6203 |pmc=7757899 |pmid=33362235|bibcode=2020PLoSO..1544068B }}</ref>

The development of explosive [[harpoon]]s and steam-powered whaling ships in the late nineteenth century brought previously unobtainable large whales within the reach of commercial [[Whaling|whalers]]. Initially, the sei whale's speed and elusiveness partially protected them,<ref name="sigurjónsson88">{{cite journal | author = Sigurjónsson, J.|year = 1988 |title= Operational factors of the Icelandic large whale fishery | journal = Rep. Int. Whal. Comm. |volume = 38 |pages = 327–333}}</ref> and later the comparatively small yield of [[Whale oil|oil]] and [[whale meat|meat]]. Once stocks of more profitable [[right whale]]s, blue whales, fin whales, and humpback whales became depleted, sei whales were hunted in earnest, particularly from 1950 to 1980.<ref name="av" />

In Iceland, a total of 2,574 whales were taken from the [[Hvalfjörður]] whaling station between 1948 and 1985. Since the late 1960s to early 1970s, the sei whale has beenwas second only to the fin whale as the preferred target of Icelandic whalers, with meat in greater demand than [[whale oil]], the prior target.<ref name="sigurjónsson88" />

[[Category:Baleen whalesBalaenoptera]]