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Significantly more fin whales killed during whaling

Julia Hager 30. October 2023 | Arctic, Science
Fin whales are the second largest whales after blue whales. With the beginning of industrial whaling in the 20th century, they became the most hunted whales in the world. (Photo: Julia Hager)

Whaling in the 20th century wiped out 99 percent of the “effective” fin whale population in the northeast Pacific, recent genetic research shows.

A research team from the University of California Los Angeles took a close look at two populations of fin whales in the eastern North Pacific and the Gulf of California by analyzing the whole genomes of 50 fin whales. The goal of the study was to better understand their history and the effects of natural and human-induced sharp population declines that lead to so-called genetic bottlenecks.

The team reports in the journal Nature Communications that during whaling in the 20th century, 99 percent of the population in the northeast Pacific was killed, not 70 percent as previously thought. Before industrial whalers shifted their focus to the large fin and blue whales in the 20th century, the “effective”, i.e. reproductive, population of fin whales comprised just under 24,000 animals for thousands of years. After the end of whaling in the 1980s, there were just 305 fin whales left.

But the researchers also have good news: despite this near extinction of the population in the eastern North Pacific, there is enough genetic diversity among the remaining whales that current conservation measures should be sufficient for the population to recover without inbreeding.

While the oceans must have been teeming with whales over 100 years ago, some 40 years after the end of whaling, it is a great luck to see them. (Photo: Julia Hager)

Such a massive population decline also poses another danger: the accumulation of harmful genes. Due to small population sizes, carriers of such deleterious genes are generally forced to mate with each other, which over time can affect the health of the overall population and lead to extinction. However, according to the study, fin whales in the northeast Pacific still have many different versions of many genes, so harmful genes are not widespread. One of the reasons is the relatively long generation time of fin whales of about 26 years. Thus, “only” two generations of whales experienced the most intense, 50-year phase of whaling, and there was not enough time for the harmful genes to accumulate.

However, the authors also point out that the Northeast Pacific population may lose its adaptive potential to climate change or diseases if the population remains relatively small. Therefore, researchers see it as essential to maintain the whaling moratorium and conservation measures to allow the population to grow.

Fin whales were most heavily hunted during industrial whaling. About 874,000 fin whales were killed worldwide between 1900 and 1989, including more than 75,500 in the North Pacific.

Julia Hager, PolarJournal

Source Sergio F. Nigenda-Morales, Meixi Lin, Paulina G. Nuñez-Valencia, et al. The genomic footprint of whaling and isolation in fin whale populations. Nature Communications, 2023; 14 (1) DOI: 10.1038/s41467-023-40052-z.

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