Vaquita: World's most endangered sea mammal 'not doomed'

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Vaquita porpoise, mother and calfImage source, Paula Olson
Image caption,
The porpoise is teetering on the brink of extinction

The world's rarest sea mammal still has a chance of survival, despite numbering only about 10 in the wild, according to a genetic study.

The vaquita porpoise is teetering on the brink of extinction, but scientists say DNA tests show the population is still genetically viable.

The tiny silvery porpoise lives only in Mexico's Gulf of California.

However, it faces an existential threat from being caught in large weighted nets, known as gillnets.

"Our study very clearly shows that the vaquita has a really good chance of avoiding extinction, if we are able to protect it, by removing the gillnets from its habitat," said study researcher, Dr Jacqueline Robinson of the University of California, San Francisco.

There was no reason to think the vaquita was "doomed" simply because it has small population sizes or low genetic diversity, she said. "It really comes down to our choices and actions in terms of giving the vaquita the best chance at surviving."

Image source, PA Media
Image caption,
An undated photo shows a dead vaquita porpoise entangled in a gillnet set for a totoaba

Some had given up on saving the vaquita, thinking that even if the species could be protected from fishing pressures, the health effects of in-breeding would wipe it out.

But the study, published in Science, found the vaquita is not "genetically compromised" and should be able to bounce back from near extinction, if its habitat is fully protected.

"They have a very high chance of making it over the next 50 years, if they receive complete protection," said Dr Robinson.

The researchers analysed DNA from vaquitas caught between 1985 to 2017, which are closely related to the ones alive today. And they developed a computer model to predict how the population might change over the next 50 years, based on their genetic findings.

Because the species has been rare for a long time, with naturally low levels of genetic variation, the risks from in-breeding are reduced, the researchers say. And they believe there are lessons for other endangered species, such as those living on islands or with a limited range.

But saving the vaquita will not be easy, given past tensions between conservationists and locals, and diplomatic friction over the enforcement of fishing bans by the Mexican government.

Attempts to ban gillnets have met opposition from fishing communities. And illegal trade in a fish called the totoaba has contributed to the demise of the vaquita and other marine species, which get entangled in the nets.

Totoaba was a food source before it was placed on Mexico's endangered list.

The swim bladder, an organ that helps the fish stay afloat, is highly prized in China for its perceived - though unproven - medicinal properties.

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