Southern Africa: Sightings of Blue and Fin Whales Increase in South-East Atlantic
Research led by the University of Cape Town’s (UCT) Centre for Statistics in Ecology, Environment and Conservation, revealed a recent increase in sightings of the world’s two largest whale species in the southeastern Atlantic.
The research findings were published in the African Journal of Marine Science and compiled more than 60 years of confirmed sightings and strandings from Namibia and South Africa’s West Coast. The study focused on Antarctic blue whales and fin whales, both heavily targeted during the industrial whaling era.
“Our results provide important evidence that these giants of the ocean are slowly recovering from the devastating impact of 20th century commercial whaling, which pushed them to the brink of extinction,” said lead author Dr Bridget James from the Centre for Statistics in Ecology, Environment and Conservation. “Sightings remain rare, but they are becoming more frequent than in previous decades, and with sustained protection there is reason to believe this recovery can continue.”
Nursery area for blue and fin whales
It’s believed that between 1913 and 1978, an estimated 350 000 blue whales and 750 000 fin whales were killed – causing dramatic global population declines. Today, Antarctic blue whales are still listed as critically endangered by the International Union for the Conservation of Nature Red List. Their population is currently estimated at around 3% of the pre-whaling numbers – increasing slowly at about 5-8% per year. Fin whales on the other hand are classified as vulnerable, with populations thought to have recovered to more than 30% of historical levels and growing at about 4-5% annually.
“Historic whaling data suggests that the southeast Atlantic may once have been an important nursery area for both blue and fin whales.”
Despite these signs of improvement, both species remain difficult to study as they roam vast distances and spend much of their lives in remote Antarctic waters. Data from migration routes and potential breeding grounds, including the southeastern Atlantic, has been particularly limited.
“Historic whaling data suggests that the southeast Atlantic may once have been an important nursery area for both blue and fin whales. But until now we have had very little consolidated information on their more recent presence in this region,” Dr James said.
Plugging the gap
To plug the gap, researchers compiled verified sightings and strandings recorded between 1964 and March 2025. These focused on the Benguela upwelling ecosystem – a nutrient-rich region off Namibia and the West Coast of South Africa – to better understand trends in presence and seasonality.
Blue whales, James said, were recorded infrequently – with 12 sightings, one stranding and five additional published records. They were most often seen between late spring and autumn. Fin whales were encountered more often – with 76 sighting and six strandings and were seen all year round.
“As population slowly rebuild, we would expect to see these whales reoccupying parts of their historical range,” said co-author Dr Simon Elwen, the director of Sea Search and a research associate at the Department of BotZoo at Stellenbosch University. “The increase in sightings and strandings is consistent with this gradual recovery, although increased offshore observation efforts may also contribute.”
Threats remain
While these sightings are reassuring, researchers caution that recovery does not mean that threats have disappeared. Large whales remain at risk from ship strikes, entanglement in fishing gear, underwater noise, pollution and climate-driven changes in ocean ecosystems.
“Signs of a return to the southeast Atlantic do not signal full recovery for blue and fin whales, and these populations have a long way to go to reach their historic numbers,” said James.
And Elwen agreed.
“They point to resilience – but it should be emphasised that both species remain vulnerable to modern human pressures and highlight that even with more than 50 years of recovery since the end of commercial whaling, we could only compile 12 records of blue whales off our coast.”
James noted that part of the recently overserved increase in sightings might be related to an increase in observation efforts and reporting, especially records from marine wildlife observers working off seismic survey vessels looking for oil and gas.
“There is still a shortage of the type of systematic scientific monitoring around our coasts, that is needed to accurately assess the populations of these two species in the southeast Atlantic.”
“There is still a shortage of the type of systematic scientific monitoring around our coasts, that is needed to accurately assess the populations of these two species in the southeast Atlantic,” she said.
Authors recommend expanding passive acoustic monitoring, increasing trained observer coverage in commercial sectors and incorporating whale distribution data into marine spatial planning to safeguard this slow but important recovery.
By UCT.
