Antarctic hotspot: fin whales prefer the waters around Elephant Island
During the days of commercial whaling, fin whales were hunted so intensively that only a small percentage of the southern hemisphere’s population survived, and even today, marine biologists know little about it. the life of the second largest whale in the world. This makes the findings of researchers at the Alfred Wegener Institute, the Helmholtz Center for Polar and Marine Research (AWI) and the Johann Heinrich von Thünen Institute for Marine Fisheries, which show that large numbers of baleen whales regularly frequent waters rich in krill. surrounding Elephant Island, all the more welcome. Evidence of this is provided by underwater sound recordings from the region, where, at the peak of May, so many fin whale vocalizations can be heard that the individual calls merge into a veritable chorus of sound, as is now reported. the research team in the newspaper. Royal Society Open Science. With this in mind, marine biologists are calling for protective measures for this important habitat so as not to jeopardize the apparent recovery of the fin whale population.
Fin whales are still rare and, according to textbooks, normally appear in groups of three to a maximum of seven. As such, AWI marine biologist Elke Burkhardt was all the more surprised that in the end. In the southern summer of 2012, during an expedition to the Scottish Sea aboard the German research icebreaker Polarstern, she counted more than 100 hundred fin whales in the northern waters. of Elephant Island. Was this a chance find or did it mean that so many of the world’s second largest baleen whales congregated here regularly? And if so, why?
To answer this question, Burkhardt and his team installed in January 2013 a mooring with two underwater acoustic recorders and a device to determine the food supply in the coastal area to the northwest of the island. Over a three-year period, from January 2013 to February 2016, the instruments recorded the soundscape of the underwater world and collected data on the food supply in the upper water column. In doing so, they helped identify one of the fin whale’s most important habitats.
“Our Polarstern sightings were no accident. As our results show, from December to August, whales regularly inhabit the waters around Elephant Island. Here they not only hunt Antarctic krill, but are also looking for partners. Our loggers have recorded the highest number of fin whale calls – precisely in the season when the breeding season begins for the southern hemisphere population, “reports Burkhardt.
Fin whales can be identified by the low-frequency calls typical of the species: “Humans would probably only perceive them as vibrations in the pit of the stomach, as their center frequency is around 20 hertz, which makes them exceptionally deep, ”says Burkhardt. Male fin whales that are ready to mate and want to attract females make these bass sounds at rapid, regular intervals. “Their courtship behavior may also explain why in May our instruments recorded so many of these calls that they merged and were barely discernible as individual sounds,” says the marine biologist from the ‘AWI.
New arguments in favor of a marine protected area around Elephant Island
She was delighted to discover the many fin whales around Elephant Island: “If this concentration really indicates that the fin whale population is increasing, it would represent a notable achievement for the international moratorium on whaling, which has come into effect. 35 years ago “. she explains.
At the same time, the new findings are worrying. “On the one hand, Antarctic krill is the subject of intensive fishing in the Scotia Sea; on the other hand, the area, which is extremely important for fin whales, is frequently visited by cruise ships. It is therefore all the more important to protect the waters in a comprehensive manner. around Elephant Island, and to regulate both krill fishing and tourism to avoid harming fin whale stocks, ”says Burkhardt. Accordingly, the soundscape should be recorded at regular intervals to document any changes in the population.
Where do Elephant Island fin whales spend the winter?
By analyzing the underwater recordings, the research team discovered another interesting detail: the 20 Hz pulse also contains an accompanying sound with a frequency of 86 Hz. This in turn resembles the calls of fin whales. that Chilean marine biologists had previously recorded off the coast of central Chile – especially at the time of year when Elephant Island instruments rarely recorded the sounds of baleen whales. Was it possible that the same whale population was producing sounds in both regions and moving between the South Shetland Islands, to which Elephant Island belongs, and the Pacific coast of Chile?
“Fin whales are thought to produce higher frequency, population-specific sounds, which can be used to distinguish between different populations. If so, we can probably conclude that these fin whales that inhabit the waters surrounding the fin whales. ‘Elephant Island in the south of the country. summer can give birth to their young in the warmer waters off Chile’s Pacific coast later in the year, and these whales travel regularly between the two regions,’ says Burkhardt.
However, to verify this, further studies are needed. To this end, the Bremerhaven-based research team has installed additional underwater recording devices, which will be provisionally recovered in 2022, near the island. Marine biologists are currently analyzing their underwater recordings of the period since 2016. And the first snippets are promising: In the summers after 2016, Elephant Island remained a favorite gathering place for fin whales.
Original publication: Elke Burkhardt, Ilse Van Opzeeland, Boris Cisewski, Ramona Mattmüller, Marlene Meister, Elena Schall, Stefanie Spiesecke, Karolin Thomisch, Sarah Zwicker and Olaf Boebel (2021): Seasonal and daily cycles of acoustic occurrence of fin whales near Elephant Island, Antarctica. R. Soc. Open Sci. 8: 201142. https: /
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