There are only 10 Pacific porpoises left. But saving species is still possible

They were thought to be doomed: Pacific porpoises are today the most endangered species of marine mammals. And for good reason, scientists estimate that there are only about a dozen left in the waters of the Gulf of California.

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Faced with this observation, many believed that this animal could never recover. In question, the forced kinship of future offspring. But that theory is now contradicted by a new study published Thursday in the prestigious journal Science. She stresses that despite their low numbers, porpoises do not disappear due to genetic reasons. On at least one condition: that the fishing practices responsible for their deterioration cease once and for all.

We try to counter this idea that there is no hope, and that there is nothing we can do to save them.Jacqueline Robinson, lead author of the study and a researcher at the University of California, San Francisco, told AFP. The campaign for the survival of the genre especially mobilized the actor Leonardo DiCaprio, and it became a diplomatic issue, the United States putting pressure on Mexico.

Low genetic diversity

Of the same family as dolphins, this porpoise measures on average just over one meter, making it the smallest of all cetaceans. call “Vaquita Marina(small sea cow) In Mexico, the animal lives only in a very limited area, in the north of the Gulf of California. In the twentieth century, it was destroyed by the large gillnets used for fishing in particular the endangered fish itself, the tuaba, which was much sought after in some countries. Although fishing for this fish is declared illegal, the ban is not always respected. However, porpoises get caught in these nets, causing them to die.

When they were first counted in 1997, there were actually only 570 species, and today, the species is on the verge of extinction, and some believe its fate is now doomed, due to inevitable kinship. To confirm this, the researchers analyzed the genomes of 20 porpoises, from samples taken between 1985 and 2017 (mostly from deceased individuals) and preserved since then. This allowed them to determine that Pacific porpoises have always been a rare species, with a population of only a few thousand over the past 250,000 years.

Therefore its genetic diversity is very low. The result was confirmed by comparing its genome with the genome of eleven other species (dolphins, killer whales, whales, etc.). “In general, low genetic diversity is thought to be a bad thing. But in this case, it is an advantage for porpoise survival in the Pacific OceanJacqueline Robinson explained.

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To understand the cause, it is necessary to understand the mechanism that makes inbreeding a problem. It is caused by a type of harmful genetic mutation. Having one copy of this mutation in an individual’s genetic code is not a problem. On the other hand, inheriting two copies becomes a problem for one’s health. However, the inheritance of two replicas is more likely when the parents are from the same family.

But today’s porpoises have very few of these harmful mutations in their genetic code. why? “Because its population has always been very low» Details of the researcher. “So these mutations have historically been eliminated much more efficiently than large populations, where they can persist and remain immune to natural selection.Based on this observation, the researchers then ran simulations to estimate the survival chances of Pacific porpoises. If net fishing stops completely, the risk of species extinction is only 6%. But if only the catch is reduced, the risk of extinction increases dramatically: even with an 80% reduction in catch, porpoises have a 62% chance of extinction.

If they can still be saved, there is an emergency situation, alert the researchers. “If we lose it, it will be the result of human choices, not genetic factors.,” was emphasized in a press release by Christopher Kyriasis, of the University of California at Los Angeles and co-author of the study. The scientists believe their simulations can be applied to other rare species, such as the tiger, Florida tiger and Tasmanian devil… which they also hope to bring some Hope for her.


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