• (c) FC / CW

Sei whales – distribution, abundance and ecology

Sei whales (Balaenoptera borealis) are currently classified as globally endangered by the International Union for Conservation of Nature, due to heavy exploitation by commercial whaling operations in the 1900s. Little is understood about the modern-day distribution and ecology of this species worldwide, due to its occurrence in predominantly offshore habitats (making it challenging to study) and the unpredictable fluctuations in its distribution between years.

In the Falkland Islands, Southern Hemisphere sei whales have been increasingly observed in coastal waters since the 1990s, providing a rare opportunity to initiate a field study on the species. Since October 2016, Caroline has worked for Falklands Conservation (FC), implementing several field projects on sei whales (Balaenoptera borealis) around the Islands:

  • An EU BEST 2.0 Small Grants project titled “Developing a site-based conservation approach for sei whales Balaenoptera borealis at Berkeley Sound, Falkland Islands.” The project aimed to investigate the distribution, population size and ecology of sei whales at Berkeley Sound in East Falkland during 2017;
  • A Royal Society for the Protection of Birds (RSPB) funded project investigating the genetic diversity of Falkland sei whales via biopsy sampling in 2017;
  • A survey of sei whales on the west coast of West Falkland during the 2018 field season, funded by FC, the RSPB, and the Falkland Islands Government. The project collected information on the distribution, behaviour, abundance and ecology of sei whales;
  • A Darwin Plus funded project at two sites (Berkeley Sound and Falkland Sound) during 2019 and 2020, focused on photo-identification, genetics and ecology of sei whales and of the southern right whale (Eubalaena australis).

The work carried out during the projects to date has included:

  • Visual surveys of the spatio-temporal distribution of sei whales, southern right whales (and coastal dolphins) from shore, vessel and aerial platforms;
  • Photo-identification work to identify individual whales and investigate their movements, minimum population size and associations;
  • Faecal sampling to examine diet, parasites and extract whale DNA;
  • Biopsy sampling to collect small tissue samples to carry out genetic and isotope analysis (in collaboration with the British Antarctic Survey);
  • Behavioural work to assess the dive times and surfacing characteristics of sei whales around the Falkland Islands.

The projects have provided the first systematic information on sei whale and southern right whale occurrence in the Falkland Islands, and further fieldwork is planned during 2021. Outputs, including scientific papers, will be listed below as they become available.

Publications and downloads

  • Weir, C.R., Taylor, M., Jelbes, P.A.Q., Stanworth, A. and Hammond, P.S. Distribution and abundance of sei whales off the west coast of the Falkland Islands. In Press, Marine Mammal Science.
  • Baines, M. and Weir, C.R. (2020). Predicting suitable coastal habitat for sei whales, southern right whales and dolphins around the Falkland Islands. PLOS ONE 15(12): e0244068. https://doi.org/10.1371/journal.pone.0244068
  • Weir, C.R., Oms, G., Baracho-Neto, C.G., Wedekin, L.L. and Daura-Jorge, F.G. (2020). Migratory movement of a sei whale (Balaenoptera borealis) between Brazil and the Falkland Islands (Malvinas). Marine Mammal Science, 36: 1050–1057. DOI: 10.1111/mms.12687
  • Weir, C.R. and Stanworth, A. (2019). The Falkland Islands (Malvinas) as sub-Antarctic foraging, migratory and wintering habitat for southern right whales. Journal of the Marine Biological Association of the United Kingdom, 1-11. doi:10.1017/S0025315419001024
  • Weir, C.R., Stanworth, A., Cartwright, S., Jelbes, P.A.Q., Taylor, M. and Pompert, J. (2019). Distribution and movements of sei whales (Balaenoptera borealis) on coastal feeding grounds in the Falkland Islands (Malvinas). World Marine Mammal Conference, Barcelona, Spain, December 2019.
  • Buss, D., Jackson, J. A., O’Connell, T.C., Goodall-Copestake, W.P., Carroll, E.L., Foote, A., Barnes, I., Brace, S., Stowasser, G., Trathan, P., Jelbes, P.A.Q, Taylor, M., Stanworth, A. and Weir, C.R. (2019). Understanding diet, past and present: Insights into the foraging ecology of Falkland Island sei whales using DNA metabarcoding and stable isotope analysis. World Marine Mammal Conference, Barcelona, Spain, December 2019.
  • Weir, C.R., Taylor, M., Jelbes, P.A.Q. and Stanworth, A. (2018). Cue rates and surfacing characteristics of sei whales (Balaenoptera borealis ) in the Falkland Islands. Journal of Cetacean Research and Management, 19: 43–55.
  • Weir, C.R. (2018). A preliminary assessment of endangered sei whales (Balaenoptera borealis) in two candidate Key Biodiversity Areas in West Falkland. Falklands Conservation report. Version 1.2, 3 September 2018. 128 pp.
  • Weir, C.R. (2017). Developing a site-based conservation approach for sei whales Balaenoptera borealis at Berkeley Sound, Falkland Islands. Falklands Conservation report. Version 1.0, September 2017. 115 pp.

For more information about Falklands Conservation please visit the Falklands Conservation website