From a distance, it looked like a layer of thick fog on the horizon. But as the ship got closer, the ocean was bubbling with 150 fin whales (or fin whales), the second largest animal on the planet, swooping down and launching themselves against the surface of the water.
Six weeks after starting a nine-week expedition off the coast of Elephant Island, northeast of the Antarctic Peninsula, scientists stumbled upon the largest fin whale encounter ever documented.
“It was one of the most spectacular observations of my life,” said Helena Herr, an ecologist at the University of Hamburg who studies marine mammals. “The fin whales seemed to have gone berserk from the concentration of food they encountered. It was absolutely thrilling.”
Herr and his colleagues documented in a paper published Thursday in Scientific Reports the return of fin whales in large numbers to waters that had once been their historic feeding grounds. The research brings rare good news in the otherwise troubling landscape of global biodiversity, in particular marine animal species.
Humans are accelerating species extinctions at an unprecedented rate, according to United Nations assessments. According to recent models, by 2300, global warming caused by continuous greenhouse gas emissions could trigger a mass extinction of marine species.
But the fin whale population recovery offers “a sign that if we implement management and conservation, there is a chance the species will recover,” Herr said.
The scene seen in the waters around Antarctica was very different for much of the 20th century. Between 1904 and 1976, commercial whalers invaded the fertile areas where whales feed and killed an estimated 725,000 fin whales in the Boreal Ocean, reducing the species population to just 1% of what it was before whaling began.
In 1982, when parties to the International Whaling Commission finally voted to ban whaling, after a decade-long campaign by environmentalists to save these animals, several species — including fin whales, sperm whales and swordfish—had already been virtually extinct due to hunting.
But 40 years after commercial whaling was banned, researchers studying other species in the Boreal Ocean began to notice fin whales returning in increasing numbers.
That’s what happened in 2013 for Herr and his colleagues. At the time, they were studying minke whales when they “coincidentally” came across large concentrations of fin whales. They decided to ask for funds to study the resurgence of the species.
In 2018 and 2019, researchers returned to the Antarctic Peninsula to do the first dedicated study of the fin whale population. Through aerial surveys, they recorded the presence of 100 groups of fin whales ranging in size from one to four individuals. They also documented eight large groups of up to 150 whales gathered to feed.
The study “confirms that this pattern is still continuing and is getting stronger,” said ichthyologist Jarrod Santora of the National Oceanic and Atmospheric Administration, who was studying krill when he became one of the first researchers to document growing fin whale populations (he did not participated in the new survey).
Scientists who study whales warn that not all whale species have recovered equally well since hunting was banned. Sally Mizroch, an ichthyologist who has studied whales since 1979 and was not involved in the research, described fin whales as “very successful.” Unlike other species, such as the blue whale, fin whales travel long distances to search for food and consume diverse food sources.
Scientists aren’t sure why some of the fin whale concentrations were so large. Herr noted that the scenes they witnessed had at least some parallels to historical accounts written before the widespread commercial whaling. For example, on an expedition to Antarctica in 1892, naturalist William Speirs Bruce described seeing the shores and spurts of whales stretching from “horizon to horizon.”
Recent research posits that the recovery of whale populations is positive not only for the whales, but also for the entire ecosystem. Scientists suggest that when whales feed on krill, they excrete iron, which was contained in crustaceans, back into the water. This, in turn, can increase the presence of phytoplankton, microscopic organisms that use carbon dioxide to carry out photosynthesis and are at the base of the marine food chain.
When fin whales bring krill to the surface of the water, they can also facilitate the action of other predators, including seabirds and seals, added Santora. “There’s a lot more cooperation and symbiosis in the ecosystem than we usually think.”
Translation by Clara Allain
