Blue whale numbers rebound off South Georgia

When whaling all but exterminated the Antarctic blue whale 50 years ago, the waters around South Georgia fell silent. Between 1998 and 2018, dedicated whale surveys off the sub-Antarctic island yielded a sole blue whale sighting. But a whale expedition this year and analysis by an international research team resulted in 58 blue whale sightings and numerous acoustic detections, raising hopes that the critically endangered mammal is finally recovering five decades after whaling was banned.

“We don’t quite know why it has taken the blue whales so long to come back,” said Susannah Calderan of the Scottish Association for Marine Science and lead author of a study in the journal Endangered Species Research. “It may be that so many of them were killed at South Georgia that there was a loss of cultural memory in the population that the area was a foraging ground, and that it is only now being rediscovered.”

Blue whales were once abundant off South Georgia before industrial whaling was established on the island in 1904. An estimated 42,698 whales were killed there, with most slaughtered before the mid-1930s. Despite the establishment of legal protection in the 1960s, illegal hunting continued until the early 1970s.

Gathering Data

Acoustic and sightings data was gathered off South Georgia on expeditions led by the British Antarctic Survey, the Swiss Polar Institute Antarctic Circumnavigation Expedition and the government of South Georgia, with funding from groups including the Friends of South Georgia Island.

As well as searching for whales, researchers used listening devices to detect their loud low-frequency calls over long distances. The team also compiled records of whale sightings reported to the South Georgia Museum by mariners and tourist ship passengers, and photos enabling individual animals to be identified.

Between 2011 and 2020, 41 different blue whales have been photo-identified from South Georgia, none of which match the 517 whales in the current Antarctic blue whale photographic catalogue. Additional research has revealed that humpback whales are also returning to the region.

“This is an exciting discovery and a really positive step forward for the conservation of the Antarctic blue whale, “ said Dr Jennifer Jackson of the British Antarctic Survey and leader of the 2020 whale expedition. “With South Georgia waters designated as a marine protected area by the government of South Georgia and the South Sandwich Islands, we hope that these increased numbers of blue whales are a sign of things to come and that our research can continue to contribute to effective management of the area, ” she added.