Sightings of blue whales and fin whales off Southern Africa’s Atlantic coast have increased in recent years, according to a newly published study.
This could signal recovery of the marine mammals after being virtually eliminated from the area by commercial whaling in the 20th century, the study authors say.
Scientists estimate around 350,000 Antarctic blue whales (Balaenoptera musculus intermedia) and some 725,000 fin whales (B. physalus quoyi) were killed in the Atlantic during the industrial whaling era from 1913-1978, driving both whales to near extinction.
A research team led by Bridget James of the University of Cape Town, South Africa, set out to assess if both subspecies are recovering in the Benguela ecosystem in the southeastern Atlantic. It’s a stretch of water between the west coasts of northern Angola, Namibia, and South Africa, where currents bring nutrients from lower ocean depths to the surface, producing rich blooms of krill, a marine crustacean that both whale subspecies eat.
The team found that between 1964 and March 2025, there were 17 reports of blue whale sightings and one report of stranding in the region.
They also recorded 76 fin whale sightings and six strandings. The blue whales were most often seen between late spring to summer (October-December) and autumn (March-April) in the Benguela ecosystem, while fin whales were seen year-round.
While the number of sightings is still relatively low, 95% of them were recorded since 2012.
Oregon State University/Flickr (CC BY-SA 2.0)
James told Mongabay by email that the Benguela ecosystem is a migratory corridor between breeding and feeding grounds for the whales, and that increased whale sightings are an expected indicator of populations recovery.
Current Antarctic blue whale populations are estimated to be around 3% of pre-whaling numbers, while fin whale numbers have recovered to more than 30% of historical levels.
James said increases in their populations to at least 50% of pre-whaling abundance would suggest successful recovery for both subspecies. Whales have relatively few offspring and long intervals between births, which makes their recovery times very slow.
James added that as whale numbers increase, they’ll face further challenges since the ocean now is a very different place than during whaling times, with many more large ships and industrial and vessel noise. She noted one blue whale had died off Namibia possibly due to a ship strike.
Asha de Vos, a blue whale expert from Sri Lanka, not affiliated with the study, told Mongabay by email that “similar trends have been observed in other parts of the world following the end of commercial whaling.” She added these trends “are often consistent with gradual population recovery and the reoccupation of historical habitat.”
De Vos said an increase in sightings could also reflect more whales traversing the region rather than an absolute recovery of numbers, and that the findings provide promising evidence that warrants continued long-term monitoring.
Featured Image: Courtesy of Sara Golaski/Namibian Dolphin Project
This article was originally published on Mongabay.
