For four decades, the world's largest animals have been slowly reclaiming the ocean. Now, researchers have the numbers to prove it.
A new study published this week finds that sightings of Antarctic blue whales and fin whales off the southern coast of Africa have surged dramatically — with 95 percent of all recorded sightings for both species occurring since 2012. The findings coincide with the 40th anniversary of the international commercial whaling moratorium that came into force in 1986.
The research, led by scientists at the University of Cape Town, South Africa, chronicled sightings from waters off the southern African coast. Although the total number of recorded sightings remains relatively modest, the trend is unmistakably upward and "steadily increasing as these whale populations recover," the study noted.
The Scale of What Was Lost
To understand how significant this recovery is, it helps to understand the scale of what was lost. Commercial whaling in the 20th century was one of the most devastating wildlife slaughters in recorded history. At its peak in the 1960s, more than 60,000 whales were killed in a single year.
Antarctic blue whales — the largest animals ever known to have existed on Earth, capable of reaching 30 metres in length and 200 tonnes in weight — were reduced from an estimated 300,000 individuals to fewer than 400 by the 1970s. They were, in effect, commercially extinct. Fin whales, the second-largest species, fared somewhat better but also suffered catastrophic losses.
The 1986 moratorium, passed by the International Whaling Commission after years of campaigning by conservation organisations worldwide, marked a turning point. Commercial whaling ceased for most nations — though Japan, Norway, Iceland, and the Faroe Islands have continued to hunt whales under various exemptions.
A Slow, Steady Comeback
Despite those ongoing hunts, the overall number of whales killed globally has fallen dramatically. Data shows that whale kills hit a historic low in the past decade.
For Antarctic blue whales and fin whales, recovery has been slow by biological necessity. These are long-lived, slow-reproducing animals: blue whales don't reach sexual maturity until around age ten, and they typically give birth to just one calf every two to three years. Population recovery, when it comes, takes generations.
The consistent sightings now being recorded off South Africa — waters that were once prime hunting grounds — are considered a significant marker of progress. Researchers are optimistic, while cautioning that full recovery to pre-whaling levels is still a long way off.
More Whales, Healthier Oceans
The recovery of whale populations carries benefits that extend far beyond the species themselves. Whales play a critical role in ocean ecosystems, cycling nutrients between deep and shallow waters through their feeding, diving, and migration patterns. Their waste fertilises phytoplankton, which forms the base of the marine food web and absorbs significant amounts of carbon.
A world with more whales is, in a real sense, a healthier world. And after 40 years of protection, the ocean is beginning to respond.
What Comes Next
Conservationists caution that the work is far from complete. Antarctic blue whale populations are estimated at only a few thousand individuals — a fraction of their pre-whaling numbers. Climate change poses a new threat: warming oceans, shifting prey distributions, and increasingly acidic waters all challenge the recovery that decades of protection have enabled.
But for scientists watching the sighting records climb year by year off the coast of South Africa, the trend is unmistakable. The ocean's giants are coming back — and the anniversary of the moratorium is a fitting moment to acknowledge how far they have come.
