Whaling in the 20th century led to a significant decline in the genetic diversity of ocean giants, with particularly devastating effects on two species.
The commercial whaling industry has spent centuries slaughtering whales around the world for their oil and meat, decimating some populations and pushing many species to the brink of extinction.
that International Endowment Commercial whaling eventually helped stop the slaughter; Some residents are even beginning to recover modestly. However, according to a new study, the grim legacy of the whaling era still haunts the descendants of survivors.
Researchers discovered this by examining whale bones found on beaches near abandoned whaling stations on South Georgia Island in the South Atlantic Ocean. Some of the bones are more than 100 years old, but are well preserved due to the cool tundra climate of South Georgia.
The international team compared DNA from those ancient bones with DNA from whales living in the area today, focusing on three South Atlantic species: blue, fin, and humpback whales.
Their findings suggest that whaling in the last century had a significant impact on the color blue in particular (Palaenoptera muscle(and humpback whales)Megaptera novangelii), which appears to have lost all of its maternal lineage DNA.
“Maternal lineage is often linked to an animal’s cultural memories, such as feeding and breeding sites passed down from one generation to the next.” He says First author and marine ecologist Angela Sremba of the Marine Mammal Institute at Oregon State University.
“If the maternal lineage is lost, that knowledge will likely be lost as well.”
As whale numbers declined elsewhere, commercial whalers increasingly targeted the Southern Hemisphere in the early 20th century, establishing whaling stations in remote places such as South Georgia, located about 1,300 kilometers east of the Falkland Islands.
Between the turn of the century and the 1960s, whalers killed more than two million whales in the Southern Hemisphere alone, including about 175,000 whales off South Georgia.
The researchers noted that the island hosted numerous whaling stations during that period, and its landscape remains littered with thousands of washed-up whale bones that were discarded into the ocean once the carcasses were processed.
Although some whale populations in the South Atlantic are now recovering, many remain well below their estimated pre-whaling numbers, due to the scale of the carnage in the past century as well as the slow reproductive rates of large baleen whales like these.
These large whales are still rarely seen in some of the habitats frequented by their ancestors, including the waters around South Georgia. Researchers say this suggests that populations may have been extirpated or locally extinct.
“For 60 years, whales have been absent from feeding grounds in South Georgia, indicating a loss of cultural memory.” He says Scott Baker, a marine biologist at the Oregon Marine Mammal Institute.
He added, “The numbers of whales returning to this area today are still not large.” Add“But there is a feeling that they may be rediscovering this habitat.”
Modern blue, hump and fin (Balanoptera PhysalusThe study found that whales in these waters still have fairly high genetic diversity, which justifies at least cautious optimism about their overall recovery.
However, among blue whales and humpback whales, comparison of DNA from early 20th-century bones with DNA from modern whales suggests a loss of ancient maternal DNA lineages.
Most whales alive today are likely descendants of whales that faced this onslaught from humans, but as Sremba points out, some survivors of the era of commercial whaling may still be out there.
Many large whales are known for their impressive longevity, and the three species examined in this study can live for 90 years or more.
Any early 20th century survivor would be nearing the end of their life span, and as they died, that could mean losing more maternal DNA lines.
This adds a sense of urgency to such studies, Sremba says, noting that we have a fleeting opportunity to record genetic information about these older whales while they are still with us.
“It is remarkable that these species survived,” she said. He says. “In another 100 years, we don’t know what might have changed, and we can’t measure any change now if we don’t have a good understanding of the past.”
By helping us reconstruct the history of whale populations, this type of research can shed more light on what has been lost to commercial whaling, and can bolster efforts to protect what has not, researchers say.
Although South Georgia’s cold climate helped preserve the DNA in these bones for researchers to study a century later, this protection may fade as temperatures rise on the island due to climate change, Baker notes.
He added: “This work is a way to preserve this history indefinitely.” He says.
The study was published in Journal of Genetics.
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