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A recent rise in dolphin deaths in the Black Sea may have been caused by the war in Ukraine, scientists have said, Selin Uğurtaş reports.
Researchers believe heightened noise pollution in the northern Black Sea, caused by about 20 Russian navy vessels and ongoing military activities, may have been driving cetaceans south to Turkish and Bulgarian shores, where they are being stranded or caught in fishing nets in unusually high numbers.
Since the beginning of the war, Turkey has recorded a rise in strandings of the common dolphin (Delphinus delphis) across its Black Sea coast. More than 80 of the animals were found dead across the country’s western Black Sea, which the Turkish Marine Research Foundation (Tudav) described as “an extraordinary increase”.
Initial investigations by Tudav revealed about half of these dolphins were killed after getting entangled in fishing nets. The fate of the other half, however, is still an “unanswered question”, according to Dr Bayram Öztürk, the chair of Tudav, as no signs of entanglement or gunshot wounds could be found on the carcasses.
“Acoustic trauma is one of the possibilities that come to mind,” Öztürk said, although he stressed it was important to remain cautious. “We don’t have proof on what low frequency sonar may cause in the Black Sea because we have never seen this many ships, and this much noise for such an extended time – and science always demands proof.”
Navies commonly rely on sonar to detect enemy submarines from great distances. Because marine mammals also depend on sound for communication and other functions, the underwater noise can have serious, even fatal, effects on cetaceans.
According to Dr Pavel Gol’din, a researcher at Ukraine’s National Academy of Sciences, while acoustic trauma may explain the strandings, constant underwater noise caused by military activities could explain the higher bycatch rate.
Related: Ukraine war may be causing rise in dolphin deaths, say scientists