Despite Mexico''s population shrinking to 10, this is the world''s most comprehensive genetic estimate of the vaquita.
On Thursday, researchers from 20 vaquitas said that while the species possesses very little genetic diversity differences in the DNA among the various individuals, the number of potentially harmful mutations that might put its survival at risk was quite low.
The vaquita, first described by scientists in 1958 and now critically endangered, is the smallest cetacean, with its wide range of whales, dolphins, and porpoises, reaching 5 feet (1.5 metres) long and 120 pounds (54 kg). Its torpedo-shaped body is gray on the inside and white on the underside with a dark ring around the eyes.
Using computerized experiments to predict extinction risk, vaquitas, whose population has dropped more than 99 percent since the beginning of the twentieth century due to human activities, have a significant chance of rebounding if fishing gillnets are completely eliminated from their habitat. Gillnets, a large band of netting that hang in the water, are used to catch fish and shrimp but have also killed many vaquitas that have become embroiled and drown.
"Our key findings are that genetics doomed the vaquita to extinction, as some have begun to assume," said a UCLA ecology and evolutionary biology doctoral student. "These findings are important because they offer hope for a species on the brink of extinction, one that many are now abandoning."
Poaching of an endangered fish called the totoaba is a major concern for the gillnet. In China, totoaba swim bladders, believed to be a fertility enhancer, are renowned.
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"Dried totoaba swim bladders are shipped on the black market in China for traditional medicinal purposes, and they fetch a higher price than cocaine," said a research geneticist at the US National Oceanic and Atmospheric Administration''s Southwest Fisheries Science Center.
The Vaquitas, which is still evolving despite their modest numbers, inhabit the northern Gulf of California, also known as the Sea of Cortez, between mainland Mexico and the Baja peninsula.
"Gillnet fishing in the vaquita''s habitat has been banned, but the restriction has not been enforced, and vaquitas have continued to perish in nets," says research co-director Jacqueline Robinson, a postdoctoral researcher at the University of California and the Institute for Human Genetics.
The first population estimate, conducted in 1997, revealed that there were about 570 vaquitas. Since then, the population has decreased by up to half the year.
The vaquita population was already relatively small about 5,000 individuals for hundreds of thousands of years before the crash caused by human activities, making low genetic diversity a natural feature of the species.
It also revealed that there has been relatively little inbreeding among vaquitas and very few harmful recessive mutations that may lead to congenital deformities when inbreeding that might stifle species survival lower than 11 other cetacean species assessed.
In recent decades, one Cetacean species appears to have been led to extinction by humans: the baiji or Chinese river dolphin.
"It''s very unlikely that the vaquita is in danger of disappearing before we even know what we''re losing," Robinson said. "The species is in danger of going extinct, and there is no replacement it once it''s gone."
Thomson Reuters 2022