Taxonomy
Balaenoptera borealis | Sei Whale
Distribution
Status
Conservation status
| HABITATS DIRECTIVE ARTICLE 17 REPORTING |
| Range | Favourable |
| Population | Unknown |
| Habitat | Favourable |
| Future Prospects | Unknown |
| Overall Assessment of Conservation Status | Unknown |
| Overall Trend in Conservation Status | N / A |
IUCN Conservation Status |
| Ireland | Not Evaluated* |
| Europe (1) | Endangered (D) |
| Global (2) | Endangered (A1ad) |
* There is currently no Irish Red List for Marine Mammals.
Legal status
Protected by the following legal instruments:
- Habitats Directive (92/43/EEC) Annex IV
- Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix II*
- Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention) Appendix I & II
- Convention on Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix I
- International Convention for the Regulation of Whaling 1946 (as amended)
- Council Regulation (EC) No. 812/2004
- Wildlife Act (1976)
- Wildlife (Amendment) Act (2000)
- Whale Fisheries Act 1937
Native status
Sei Whales, in the east North Atlantic, are believed to migrate between summer grounds at higher latitudes and winter grounds between the Bay of Biscay and north west Africa.
Source: Harris S., Yalden D.W. 2008.
The 2008 IUCN Global Red List for this species lists Ireland as one of
the countries where it is native, however it probably better described
as a migrant in an Irish context.
Sources: Reilly, S.B. et al 2008.; de Klem, 1994
Species Biology
Identification
- Average length adult female: c.14.5m
- Average length adult male: c. 14m
- Maximum length adult: 19.5m
- Calf birth length: c. 4.4m
- Calf birth-weight: 680kg
- Average adult weight: c. 20-30 tonnnes.
- Blow: Narrow cloud, 3m high, but bushier than that of Fin Whale
- Head: Slender head, single longitudinal ridge extends from blowhole to snout, head size can be between 1/5 and 1/4 of it's body size
- Dorsal fin: The dorsal fin is well-defined, slender, erect, and slightly hooked and is located about two-thirds back along the body.
- Colouration: It is a mottled blue to grey dorsal side, with paler grey to white underside, often scared by parasites
- Markings: Distinctive throat grooves, 32-62 usually end just behind flippers, two distinctive blowholes, narrow pointed snout.
Habitat
The Sei Whale appears to be much more a pelagic species than other Balaenopterids, being found in deep, offshore waters in polar, temperate, to sub-tropical latitudes worldwide.
Source: Harris S., Yalden D.W. 2008.
Habitat includes but is not necessarily limited to;
- Open marine water (MW1)
Sources: Harris S.,Yalden D.W., 2008; Fossitt, J.A., 2001.
Reproduction
- Estimated life expectancy: c. 65 years.
- Female sexual maturity: 6-12 years.
- Male sexual maturity: c. 7-12 years.
- Mating : Winter.
- Gestation: Approximately c.10 - 13 months.
- Calving : Winter.
Calving interval is thought to be two to three years, with calves weaned at between six and nine months.
Source: Irish Whale and Dolphin Group.
Threats faced
| THREAT | ARTICLE 17 THREAT CODE | RANKING |
| Seismic exploration, explosions | H06.05 | Medium |
| Fishing and harvesting aquatic resources* | F02 | Low |
| Death or injury by collision | G05.11 | Low |
| Noise nuisance, noise pollution | H06.01 | Low |
| Changes in abiotic conditions | M01 | Low |
*This would include the threat to this species of a reduction in prey availability as well as the threat of becoming by-catch / accidental catch and also entanglement in fishing gear.
These threats accord well with threats outlined in the 2007 European Regional IUCN Red List assessment for the species which did not identify any other threats that may be relevant in Irish waters.
Source: IUCN SSC Cetacean Specialist Group 2007.
Conservation actions
In the Article 17 Habitats Directive reporting for the period 2007-2012 no Conservation Measures in place or in the process of being implemented during the period were listed for this species.
Source: NPWS 2013.
Apart from an acknowledgement of the existence of legislative protection, there are no suggested or other reported Conservation Actions in the 2007 European Regional IUCN Red List assessment or the 2008 Global IUCN Red List assessment for this species that may be relevant in Irish waters.
Sources: IUCN SSC Cetacean Specialist Group 2007; Reilly, S.B. et al 2008.In a 2009 Cetacean Action Plan a total of 41 Actions were identified as part of the plan. The plan and the 2013 review of the plan are available from the NPWS website.
Source: DEHLG 2009.
Distribution
World distribution(GBIF)
Worldwide distribution, but mostly in deep temperate waters. Not normally found in extreme polar waters although sub-arctic and sub-Antarctic are favoured summer feeding grounds. Little is known about their migration but they appear to move to lower latitudes in winter. This species is essentially a dweller of the open ocean, not generally found inshore or in coastal waters. The Sei Whale tends to follow shelf contours and plankton gatherings.
Source: Irish Whale and Dolphin Group.
Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.
Irish distribution
Occasionally observed from headlands around the winter period off the Cork coast with sightings off the west coast in mid-Autumn.
Source: Irish Whale and Dolphin Group.
This species can be difficult to identify which may explain why it is rarely recorded in coastal waters around Ireland. Mostly recorded from deeper waters ( over 200m depth) in for example the Rockall Trough. Sei whales sightings have been made in British waters in the summer.
Source: Harris S., Yalden D.W. 2008.
Temporal change
Records submitted to Data Centre in 2024
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
The National Biodiversity Data Centre is trying to
improve our knowledge on the distribution of the Sei Whale in
Ireland. Should you observe this species, please submit
sightings to add to the database. Detailed observations will assist us
gaining a better insight into where the species
is most abundant in Ireland and we might also be able to detect
regional variations. Please submit any sightings and photographs at:
http://records.biodiversityireland.ie/index.php
All
records submitted online can be viewed on Google Maps – once checked
and validated these will be added to the database and made available for
conservation and research.
Further information
For further information contact Dr. Liam Lysaght llysaght@biodiversityireland.ie
References
Publications
DEHLG 2009 Conservation Plan for Cetaceans in Irish waters.
de Klem, Cyrille, 1994. ‘The Problem of Migratory Species in International Law’, in Helge Ole Bergesen and Georg Parmann (eds.), Green Globe Yearbook ofInternational Co-operation on Environment and Development 1994(Oxford: Oxford University Press), 67–77.
Fossitt, J.A. (2001) A Guide to Habitats in Ireland. The Heritage Council
Harris S., Yalden D.W. (2008). Mammals of the British Isles :Handbook, 4th Edition. The Mammal Society.
Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team 2007. Balaenoptera borealis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 16 October 2014.
NPWS (2013) The Status of EU Protected Habitats and Species in Ireland. Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.
NPWS (2013a) Delivery Schedule for Actions listed in the Conservation Plan for Cetaceans in Irish waters – June 2013
Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Balaenoptera borealis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 16 October 2014.
Wall, D., Murray, C., O’Brien, J., Kavanagh, L., Wilson, C., Ryan, C., Glanville, B., Williams, D., Enlander, I., O’Connor, I., McGrath, D., Whooley, P. & Berrow, S. (2013). Atlas of the Distribution and Relative Abundance of Marine Mammals in Irish Offshore Waters: 2005 – 2011. Irish Whale and Dolphin Group, Kilrush, Co. Clare.Relevant links
Additional comments
This species was exploited commercially from the late 19th century until the mid- to late 20th century. The eastern North Atlantic population is very much depleted, to the point virtual absence.
Source: IUCN SSC Cetacean Specialist Group 2007.