Having narrowly escaped extinction, there are now signs that the population of the world’s second largest animal is recovering: Researchers have observed as many as 150 fin whales eating together in Antarctica. As they pointed out, the return of the sea giants is doubly satisfying. Since they play an important role in nutrient recycling in the Southern Ocean, other species in the ecosystem also benefit from recovery.
Rarely missed: fin whales are the largest animals on Earth after blue whales – and like their relatives, commercial whaling has become almost a solution to them: there was only a small part of the indigenous population of fin whales until the fishing quota was finally set to zero in 1976. But stocks of nearly 22 meters long and 70 tons of animals recovered only slowly. After seeing more animals again during individual expeditions in the 2000s, the research team led by Bettina Meyer of the Alfred Wegener Institute and Helmholtz Center for Polar and Marine Research in Bremerhaven is now reporting clear indications of a recovery in stocks.
Observed “eating gatherings”
The expedition with the research vessel Polarstern was primarily aimed at investigating the effects of climate change on Antarctic krill. These shrimp, up to six centimeters long, form the basis of the food web in the Southern Ocean: they serve as food for fish, penguins, seals and baleen whales. During their explorations, the scientists finally encountered the southern fin whale (Balaenoptera physalus quoyi) as well as schools of these tiny crustaceans. To count them, they sent Polarstern’s helicopter on reconnaissance flights. During 22 missions, the scientists initially counted 100 groups of fin whales consisting of one to four animals. However, they then encountered surprisingly large groups around Elephant Island in the Weddell Sea near the Antarctic Peninsula: about 50 to 70 animals were roaming the water together. As the researchers explained, it was about the so-called feeding groups.
“I ran straight to our screen, where we can use acoustic measurement methods to see if there are swarms of krill in the water and to what extent,” says Bettina Meyer. “In fact, we were able to use the data to identify schools of krill and even see whales chasing krill. I’ve never seen so many whales in one place, and I was fascinated to watch these huge groups feeding,” says Meyer. In the year following Polarstern’s voyage, scientists and a BBC team returned to Elephant Island on a specially chartered vessel to continue observations. In the end, they even documented groups of up to 150 animals.
Enjoy recovery with added benefits
“This high animal density and the frequency of the so-called feeding assemblages, which have not been observed since whaling began, indicate a revival of the population,” explains senior author Helena Hare from the University of Hamburg. From the researchers’ perspective, banning whaling shows success. “Although we don’t know the total number of fin whales in Antarctica due to a lack of simultaneous observations, it may be a good sign that fin whales in Antarctica are recovering after nearly 50 years of outlawing commercial whaling,” Meyer said.
As the researchers point out, the return of the sea giants is not only satisfying from a whale conservation perspective: the entire ecosystem can benefit. Because fin whale secretions provide more nutrients in the upper water layers, especially iron, which in turn benefits the growth of algae and thus other organisms. The effect, known as a ‘whale pump’, could also be important in the fight against climate change: “Microorganisms that benefit from a richer supply of nutrients absorb a lot of carbon dioxide and thus make an important contribution to reducing carbon in the atmosphere,” says Mr. Scientists say carbon dioxide sequestration in one of the world’s most important marine areas could increase due to an increase in whale numbers.
source: University of HamburgAnd the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research. Specialized article: Scientific Reports, doi: 10.1038 / s41598-022-13798-7
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