After commercial whaling nearly erased them, blue and fin whales are slowly reclaiming the southeast Atlantic - Biology Plants & Animals - Ecology

Credit: Sara Golaski for the Namibian Dolphin Project

More than 40 years after the end of commercial whaling, new research reveals a recent increase in sightings of the world's two largest whale species in the southeastern Atlantic. The findings, published in the African Journal of Marine Science, compiled more than 60 years of confirmed sightings and strandings from Namibia and South Africa's west coast. Although overall numbers remain low, sightings of both species have increased markedly in recent years—with 95% of observations recorded since 2012.

"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," says lead author Dr. Bridget James, from the Center for Statistics in Ecology, Environment and Conservation at the University of Cape Town, South Africa.

"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."

Whale populations and conservation status

The study focused on Antarctic blue whales (Balaenoptera musculus intermedia) and fin whales (B. physalus quoyi), both heavily targeted during the industrial whaling era. Between 1913 and 1978, an estimated 350,000 blue whales and 725,000 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 (IUCN) 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 are currently classified as "Vulnerable", with populations thought to have recovered to more than 30% of historical levels and growing at around 4–5% annually.

Gaps in knowledge and new data

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," adds Dr. James, whose research focuses on the ecology of whales and dolphins. "But until now, we have had very little consolidated information on their more recent presence in this region."

To address this gap, the researchers compiled verified sightings and strandings recorded between 1964 and March 2025, focusing 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.

What the researchers recorded offshore

Blue whales were recorded infrequently, with 12 sightings, one stranding and five additional published records. Fin whales were encountered more often, with 76 sightings and six strandings documented. Blue whales were most often seen between late spring and autumn, while fin whales appeared to occur year-round.

"As populations slowly rebuild, we would expect to see these whales begin reoccupying parts of their historical range," says co-author Dr. Simon Elwen, Director of Sea Search and Research Associate, at the Department of BotZoo, University of Stellenbosch. "The increase in sightings and strandings is consistent with this gradual recovery, although increased offshore observation efforts may also contribute."

Ongoing threats and data limitations

The researchers caution that recovery does not mean 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," cautions Dr. James.

"They point to resilience—but it should be emphasized 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!" said Dr. Simon Elwen

While encouraging for the status of these iconic species in the Benguela region, it should be noted that at least a part of the recent observed increase in sightings might be due to an increase in observation effort 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 South-East Atlantic.

The 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. 

Provided by Taylor & Francis 

by Taylor & Francis

edited by Sadie Harley, reviewed by Robert Egan 

Source: After commercial whaling nearly erased them, blue and fin whales are slowly reclaiming the southeast Atlantic