What’s Black and White and Reveals Historic Porpoise Distributions?
Nowadays, there are many ways to study a population of marine animals: by scuba diving, by boat, by drone and by satellite. But sometimes the older method still does the trick. Concrete example: a recent study Ecology and evolution we relied on newspapers, the original printed version, to get an idea of porpoise distributions.
The only resident marine mammal in the Baltic Sea, the Baltic harbor porpoise (Phocoena phocoena), has declined over the past two centuries due to fishing, contamination and noise pollution. With approximately 500 individuals remaining, it is currently listed as critically endangered.
Researchers from Denmark and Sweden, countries bordering the Baltic Sea, examined the National Library of Sweden’s digitized newspaper archives dating from the 1700s to the early 1900s to determine the historical distribution of porpoises. Using “tumlare» (Swedish for porpoise) «marsvin” (Danish for porpoise) and associated keywords, they found 1,490 records of porpoises. After checking porpoise localities, they mapped records of what they estimate to have been 1,455 individual porpoises.
Read more: “The invisible legacy of whaling on the high seas”
The authors of the study specify in a press release that these are not scientific investigations. “These are everyday observations, but taken together they show a very different Baltic Sea,” said Magie Aiken, first author and postdoctoral fellow at the Swedish Museum of Natural History. “Although these accounts lack precision compared to modern scientific observations, they provide a unique resource for tracking the presence and distribution of species that would otherwise be inaccessible,” the researchers say.
According to newspaper reports, the porpoises lived along the entire Swedish coast, as far north as the Gulf of Bothnia, where they are now rare. They probably migrated there from the Danish coast to feed along the Swedish coast during the warmer seasons. According to current data, porpoises were also found in German, Lithuanian and Latvian waters, surrounding the northern perimeter of the Baltic. In fact, during a single hunting season in 1880, the catch of harbor porpoises in the Little Danish Sea was reported to have been 800 individuals.
Going further back into the archaeological record, harbor porpoises were even more widespread around the Baltic. Clearly, human activities have taken a toll on this declining population, as it now occupies only about a third of its original range. To reverse this trend, the study authors recommend “proactive protection and management.”
Hopefully, the conservation needs of this imperiled porpoise population will one day make headlines.
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Main image: Juulijs / Adobe Stock
