• (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 as the Sei Whale Project Officer 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.” This project aimed to investigate the distribution, population size and ecology of sei whales at Berkeley Sound in East Falkland during the 2017 field season;
  • 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. This project collected information on the distribution, behaviour, abundance and ecology of sei whales.

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

  • Visual surveys of the spatio-temporal distribution of sei whales (and other coastal cetaceans including southern right whales Eubalaena australis and dolphins) from shore, vessel and aerial platforms;
  • Photo-identification work to identify individual whales and investigate their movements, minimum population side and associations;
  • Faecal sampling to examine diet, parasites and extract 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 occurrence in the Falkland Islands, and is planned to continue during the 2019 and 2020 field seasons. Outputs, including scientific papers, will be reported here as they are finalised.


Reports resulting from the FC sei whale projects will be available to download here.

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.

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.

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