Balaenoptera borealis - Lesson, 1828
Sei Whale
Taxonomic Status: Accepted
Related ITIS Name(s): Balaenoptera borealis Lesson, 1828 (TSN 180526)
French Common Names: rorqual boréal
Spanish Common Names: Rorcual del Norte, Ballena Boba
Unique Identifier: ELEMENT_GLOBAL.2.102708
Element Code: AMAGH01020
Informal Taxonomy: Animals, Vertebrates - Mammals - Whales and Dolphins
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Mammalia Cetacea Balaenopteridae Balaenoptera
Genus Size: B - Very small genus (2-5 species)
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Concept Reference
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Concept Reference: Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at: http://www.nmnh.si.edu/msw/.
Concept Reference Code: B93WIL01NAUS
Name Used in Concept Reference: Balaenoptera borealis
Taxonomic Comments: Rice (1998) recognized northern and southern subspecies (B. borealis borealis and B. borealis schlegelii, respectively).
Conservation Status
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NatureServe Status

Global Status: G3
Global Status Last Reviewed: 15Nov1996
Global Status Last Changed: 15Nov1996
Rounded Global Status: G3 - Vulnerable
Reasons: Widespread but relatively rare throughout the world's oceans; difficult to protect due to migratory existence.
Nation: United States
National Status: N2 (19Feb1997)
Nation: Canada
National Status: NUN,NUM (11Apr2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alaska (S3), California (SNR), Florida (SNR), Georgia (SNR), Hawaii (SNR), Maine (SNR), Maryland (SNA), Massachusetts (S1), New York (SNA), North Carolina (SNA), Oregon (SNA), Rhode Island (SNRN), South Carolina (S1), Virginia (SNR), Washington (SNA)
Canada British Columbia (SHN), New Brunswick (S1S2), Nova Scotia (S1S2), Prince Edward Island (SNR)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (02Jun1970)
Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):E,DD
Comments on COSEWIC: The Pacific Ocean population designated Endangered in May 2003 and re-examined and confirmed in May 2013.
The Atlantic Ocean population designated Data Deficient in May 2003, based on a new status report.

IUCN Red List Category: EN - Endangered
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix I

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: Worldwide, but distribution and movements during much of year are poorly known. Coast of Mexico to Gulf of Alaska in the eastern North Pacific. Bering Sea to Japan and Korea in the western North Pacific. Gulf of Mexico to Davis Strait (especially off eastern Canada) in the western North Atlantic. Norway to Spain and northwestern Africa in the eastern North Atlantic. In Southern Hemisphere, Antarctic Ocean to coasts of Brazil, Chile, South Africa, and Australia. See IUCN (1991) for further details.

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Total population is estimated at less than 51,000: about 14,000 in the Northern Hemisphere (mainly in the North Pacific), 37,000 or less in the Southern Hemisphere; a survey of Antarctic waters in the summer of 1989 found only 1500 in an area where perhaps 10,000 were expected (Matthews and Moseley 1990). North Atlantic population numbers a few thousand. See IUCN (1991) for further information on population sizes.

Overall Threat Impact Comments: Populations in all oceans have been depleted by overexploitation.

Short-term Trend: Unknown
Short-term Trend Comments: Numbers have rebounded slightly if at all since most whaling was stopped by international treaty (Matthews and Moseley 1990).

Other NatureServe Conservation Status Information

Inventory Needs: Locate high use areas.

Protection Needs: Enforce ban on harvest set by the IWC and of the MMPA and ESA.

Distribution
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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Worldwide, but distribution and movements during much of year are poorly known. Coast of Mexico to Gulf of Alaska in the eastern North Pacific. Bering Sea to Japan and Korea in the western North Pacific. Gulf of Mexico to Davis Strait (especially off eastern Canada) in the western North Atlantic. Norway to Spain and northwestern Africa in the eastern North Atlantic. In Southern Hemisphere, Antarctic Ocean to coasts of Brazil, Chile, South Africa, and Australia. See IUCN (1991) for further details.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, CA, FL, GA, HI, MA, MD, ME, NC, NY, OR, RI, SC, VA, WA
Canada BC, NB, NS, PE

Range Map
No map available.

Ecology & Life History
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Basic Description: A large baleen whale.
General Description: A large dark gray baleen whale often with ovoid grayish-white scars; front edge of prominent dorsal fin is angled upward more than 40 degrees from the back; tip of snout is turned slightly downward; single ridge on rostrum; many longitudinal grooves on throat; flippers are pointed and relatively small; tail fluke is relatively small; slim and streamlined in dorsal view; with few exceptions, baleen is uniformly ash-black with fine white fringes; grows to 18.6 m in the northern hemisphere, 21 m in the southern hemisphere, with females reaching the largest sizes (largest males average a couple meters shorter than largest females) (Leatherwood and Reeves 1983).
Diagnostic Characteristics: Maximum size is less than that of fin and blue whales. Dorsal fin is decidedly taller, more falcate, and located farther forward (a little more than one-third the body length forward from the fluke notch) than in other large baleen whales. Differs from the Bryde's whale in having a taller, less sharply pointed dorsal fin and a single dorsal rostral ridge rather than three ridges. Differs from the fin whale in the more upward-angled dorsal fin (located farther forward on the body), the lack of asymmetrical lower lip coloration, lack of whitish dorsal chevrons, lack of mixed color baleen, and fewer throat grooves (32-60 vs. 56-100); dorsal fin of sei whale tends to surface simultaneously with the head, rather than later as in the fin whale. Differs from the blue whale in the less U-shaped snout and much larger and more anterior dorsal fin. (Leatherwood and Reeves 1983).
Reproduction Comments: Single calf is born usually in winter after a gestation period of about 11-12 months. Young nurse for about 5-9 months. Calving interval for individual adult females is 2-3 years. Sexually mature at an average age of 6-10 years.
Ecology Comments: Usually travels in groups of 2-5, may concentrate in larger numbers on feeding grounds.
Habitat Type: Marine
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: Y
Mobility and Migration Comments: Migrates between lower-latitude wintering grounds and higher-latitude feeding grounds. Movements in specific areas may be unpredictable (Leatherwood and Reeves 1983).
Marine Habitat(s): Pelagic
Habitat Comments: Generally in deep water; along edge of continental shelf and in open ocean.
Adult Food Habits: Invertivore, Piscivore
Immature Food Habits: Invertivore, Piscivore
Food Comments: Eats copepods, euphausiids, squid, and various small schooling fishes. May skim feed on copepods at surface or gulp feed on krill and small fishes (Leatherwood and Reeves 1983, Katona et al. 1983).
Length: 1860 centimeters
Weight: 20000000 grams
Economic Attributes
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Economic Comments: Long exploited by shore-based and pelagic whalers, with large numbers taken beginning in the late 1800s; several thousand (probably low 10,000s) were harvested annually in the 1960s and early 1970s; see IUCN (1991) for review of exploitation history. Initially hunted for oil; now desired mainly for meat for human consumption.
Management Summary
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Management Requirements: A draft recovery plan for the North Pacific and North Atlantic stocks was available in August 1998 (www.nmfs.gov/tmcintyr/prot_res.html/).
Population/Occurrence Delineation
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Group Name: Rorquals

Use Class: Not applicable
Subtype(s): Foraging Concentration Area
Minimum Criteria for an Occurrence: An area that is, or was, occupied by a recurring concentration of foraging whales. Minimally, at least two and preferably several years of observation should be used to reliably identify significant concentrations (i.e., those occupied by feeding whales more than 10 days per year). In most cases, occurrences should not be extensive areas, but rather portions of such areas that stand out as strongly meeting the occurrence criteria. Year-to-year changes in prey distribution may mean that some key sites are not occupied every year; however, occurrences should still be delineated where data indicate that the sites are important over the longer term.
Mapping Guidance: All known sightings over a period of time in an area should be collectively mapped as a single polygon feature, or multiple polygons if there are individual areas separated by more than 5 km. Individual sightings could also be mapped as source feature points within this principal EO, although this may be impractical over time. If useful, year-to-year variation in areas could be mapped as separate source feature polygons within a larger multi-year principal EO.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 30 km
Separation Distance for Suitable Habitat: 30 km
Separation Justification: Whales can travel significant distances daily. However, occurrences are defined primarily on the basis of areas predictably supporting concentrations of prey (e.g., small fish or krill) and feeding whales, rather than on the basis of distinct whale populations or specific feeding groups. Separation distance similarly refers to areas of concentrated foraging; arbitrarily set such that occurrences are manageable for conservation of prey resource.
Date: 07Feb2002
Author: Cannings, S.
Notes: Contains all members of Balenopteridae, with the exception of MEGAPTERA NOVAEANGLIAE.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 05Apr2011
NatureServe Conservation Status Factors Author: Hammerson, G., T. W. French, and T. Mabee
Element Ecology & Life History Edition Date: 11May1994
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC.

  • Banfield, A. W. F. 1974. The mammals of Canada. University of Toronto Press, Toronto, Canada. 438 pp.

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  • COSEWIC. 2003l. COSEWIC assessment and status report on the sei whale Balaenoptera borealis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 27 pp.

  • Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 1999. Canadian Species at Risk: April 1999. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario, Canada. 17 pp.

  • Connor, P.F. 1971. The mammals of Long Island, New York. NYS Museum and Science Service Bull. 416. 78 pp.

  • Falklands Conservation. 2000. Falkland Islands wildlife. Falklands Conservation. http://www.falklands-nature.demon.co.uk/wildlife/chklst.html

  • Fisheries and Oceans Canada. 2017. Action Plan for Blue, Fin, Sei and North Pacific Right Whales (Balaenoptera musculus, B. physalus, B. borealis, and Eubalaena japonica) in Canadian Pacific Waters. Species at Risk Act Action Plan Series. Fisheries and Oceans Canada, Ottawa. iv + 28 pp.

  • Follkens, P., R.R. Reeves, B.S. Stewart, P.J. Clapham and J.A. Powell. 2002. Guide to the marine mammals of the world. National Audubon Society. Knopf. 527pp.

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  • Gusey, W.F. 1976. The fish and wildlife resources of the Middle Atlantic Bight. Shell Oil Co., Houston, TX. 2nd printing. 582 pp.

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  • Horwood, J. 1987. The sei whale: population biology, ecology & management. Croom Helm, N.Y. 375 pp.

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  • Jones, J. K., Jr., R. S. Hoffman, D. W. Rice, C. Jones, R. J. Baker, and M. D. Engstrom. 1992a. Revised checklist of North American mammals north of Mexico, 1991. Occasional Papers, The Museum, Texas Tech University, 146:1-23.

  • Katona, S. K., V. Rough, and D. T. Richardson. 1983. A Field guide to the whales, porpoises, and seals of the gulf of Maine and eastern Canada. Cape Cod to Newfoundland. Charles Scribner's Sons, N.Y. 255 pp.

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  • National Marine Fisheries Service (NMFS). 2016a. U.S. Pacific Marine Mammal Stock Assessments, 2015. NOAA-TM-NMFS-SWFSC-532. 426pp.

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