Rtake a good look at this animal. If you don’t know it, learn its name, the vaquita, and locate the Sea of Cortes, those Mexican waters in the northern Gulf of California where it still swims. Remember all this, because within 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 found a 98% drop over the previous decade and estimated the total number of survivors at around 20. In an article published Thursday, May 5 in ScienceAmerican and Mexican researchers indicate that, according to the census carried out in 2021, this number has been further halved.
The cause of this tragedy is known: human greed. Their stupidity too. Long threatened by pollution and oil exploration, the vaquita is now the collateral victim of totoaba fishing. This fish – also protected – is at the heart of intense traffic, its swim bladder, prized by Chinese medicine, being traded at astronomical prices (more than 40,000 euros according to the latest estimates). The poachers’ gillnets become deadly traps for the vaquitas. “However, there is no fatality, the survival of the species is in our hands”assures Phillip Morin, researcher at the American Agency for Oceanic and Atmospheric Observation (NOAA), one of the signatories of the article by Science.
Very low genetic diversity
This assertion, the scientist supports it on the main result of the study, namely that inbreeding does not condemn the species. The objective was clearly stated: “Assess the risk of extinction of the vaquita in light of its low genetic diversity and the inevitable inbreeding to be expected” , summarizes Jacqueline Robinson (University of California at San Francisco), first signatory of the article. The team analyzed samples from 20 individuals who lived between 1985 and 2017 and sequenced their full genomes. Since marine mammals come, like us, from a father and a mother, they were able to observe any differences between these two genetic sources. They were also able to compare the genomes themselves. And finally analyze the areas of variation. Their observation is clear: the vaquitas display a very low diversity. “On average, ten times less than ours and weaker than the eleven species of whales, dolphins, porpoises to which we compared them”, explains the researcher. But this diversity has changed little over the years.
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