From a distance, it looked like a thick fog on the horizon. But as the ship closed in, the ocean boiled as 150 fin whales, the second largest creatures on the planet, dove and scurried against the water’s surface.
Six weeks into a nine-week expedition, near the coast of Elephant Island, northeast of the Antarctic Peninsula, researchers have come across the largest gathering of fin whales ever documented.
“It was one of the most spectacular sightings I’ve had,” said Helena Herr, a marine mammal ecologist at the University of Hamburg. “The fin whales seemed to be going crazy from the food load they were facing. It was absolutely thrilling.
Dr. Herr and his colleagues documented the return of large numbers of fin whales to waters that were once their historic feeding grounds in a paper published Thursday in the journal Scientific Reports. The research provides a glimmer of good news in what is otherwise a worrying landscape for global biodiversity, and ocean dweller species in particular.
Humans are accelerating extinction at an unprecedented rate, according to United Nations assessments. In the oceans, recent modeling has estimated that global warming caused by continued greenhouse gas emissions could trigger mass mortality of marine species by 2300.
The rebound in the fin whale population, however, offers “a sign that if you apply management and conservation there is a chance for the species to recover,” Dr Herr said.
For much of the 20th century, the scene in the waters around Antarctica was markedly different. Between 1904 and 1976, commercial whalers descended on the rich feeding grounds and killed an estimated 725,000 fin whales in the Southern Ocean, reducing their population to just 1% of its pre-hunting size.
When parties to the International Whaling Commission finally voted to ban whaling in 1982, after a decade-long campaign by environmental groups to save whales, a number of species – including fin whales , sperm whales and sei whales – had already been hunted to near extinction. .
But 40 years after commercial whaling was banned, researchers studying other species in the Southern Ocean have begun to notice increasing numbers of fin whales have returned.
This was the case in 2013 for Dr. Herr and his colleagues. At the time, they were investigating minke whales when they came across large congregations of fin whales “by coincidence”. They decided to apply for funding to study the rebirth of fin whales.
In 2018 and 2019, researchers returned to the Antarctic Peninsula for the first dedicated study of the fin whale population. Through aerial surveys, researchers recorded 100 groups of fin whales, ranging in size from one to four individuals. They also documented eight large groups of up to 150 whales that had come together to feed.
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The survey “confirms that this pattern is continuing and emerging even stronger,” said Jarrod Santora, a fisheries biologist with the National Oceanic and Atmospheric Administration, who was among the first researchers to document the increase in fin whale populations. while studying krill. (He was not involved in this new research.)
Whale researchers have warned that not all whale species have bounced back as successfully since the ban on whaling. Sally Mizroch, a fisheries biologist who has studied whales since 1979 and was not involved in the research, described the fin whales as “very successful”. Unlike other species, such as blue whales, fin whales can forage over great distances and feed on a variety of food sources.
Scientists don’t know why some of the gatherings were so large. Dr. Herr noted that the scenes they witnessed had at least some parallels to historical reports written before large-scale commercial whaling. For example, naturalist William Speirs Bruce described seeing the backs and breaths of whales stretching “from horizon to horizon” during an expedition to Antarctica in 1892.
Recent research has proposed that rebounding whale populations are good not only for the whales but also for the whole ecosystem, thanks to a concept known as the “whale pump”. Scientists postulate that when whales feed on krill, they excrete the iron, which was locked up in the crustaceans, into the water. This, in turn, can stimulate phytoplankton, microscopic organisms that use carbon dioxide in photosynthesis and serve as the basis of the marine food chain.
As fin whales bring krill to the surface of the water, they can also facilitate the success of other predators, including seabirds and seals, Dr Santora said. “There’s a lot more cooperation and symbiosis than what we usually give to the ecosystem.”