Look at this animal well. If you do not know it, learn its name, the Vaquita, and locate the Sea of Cortes, these Mexican waters in the north of the Gulf of California where it still swims. Remember all this, because in a few years this marine mammal, the smallest still existing, will undoubtedly have disappeared. From a few thousand to a few hundred individuals between the 1970s and the 1990s, its population continued to collapse. In 2019, a Mexican study still noted A 98 % drop in the previous decade and estimated the total number of survivors about twenty. In an article published Thursday, May 5 in Science, American and Mexican researchers indicate that, according to the census carried out in 2021, this number was still divided by two.
The cause of this tragedy is known: the greed of humans. Their stupidity too. Long threatened by oil pollution and prospecting, Vaquita is now the collateral victim of Totoaba fishing. This fish – also protected – is at the heart of an intense traffic, its natatory bladder, popular with Chinese medicine, exchanging at astronomical prices (more than 40,000 euros according to the latest estimates). The meshes of the poachers become deadly traps for the Vaquitas. “However, there is no fatality, the survival of the species is in our hands,” says Phillip Morin, researcher at the American ocean and atmospheric observation agency (NOAA), one of the signatories of the article of science.
very low genetic diversity
This assertion, the scientist supports him on the main result of the study, namely that consanguinity does not condemn the species. The objective had been clearly displayed: “Evaluating the risk of extinction of Vaquita in the light of its low genetic diversity and the inevitable consanguinity to be expected”, summarizes Jacqueline Robinson (University of California in San Francisco), first signatory of the article. The team analyzed samples from 20 individuals who lived between 1985 and 2017 and sequenced their complete genome. The marine mammals being from, like us, from a father and a mother, they were able to observe the possible differences between these two genetic sources. They were also able to compare the genomes themselves. And finally analyze the variation areas. Their observation is clear: the Vaquitas display a very low diversity. “On average, ten times less than ours and lower than eleven species of whales, dolphins, porpoises to which we have compared them,” explains the researcher. But this diversity has evolved little over the years.
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