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(CNN)The world's smallest marine mammal is so critically endangered that there are only about 10 remaining in its sole habitat of Mexico's Gulf of California.
But that may not yet spell doom for the vaquita porpoise, according to new research.
Vaquitas have been pushed to the brink of going extinct due to illegal gillnetting, which is used to capture shrimp and totoaba fish that share the same habitat as the porpoises. The vaquitas, about 4 to 5 feet (1.2 to 1.5 meters) in length, end up as "bycatch" since they aren't the intended target of the nets.
The totoaba fish, whose status is vulnerable on the International Union for Conservation of Nature Red List of Threatened Species, has a swim bladder that is prized in China and used for traditional medicine -- and even seen as a financial investment. Mexico has outlawed totoaba fishing and made gillnetting illegal where the vaquitas live, but the practice continues unabated.
With such a small population left, researchers have questioned if vaquitas were at a greater risk of extinction due to inbreeding.
Scientists Barbara Taylor and Lorenzo Rojas-Bracho, who have been studying this risk for more than 20 years, published a 1999 paper suggesting that the "doom hypothesis" of inbreeding could not be confirmed. This is important because if an animal is considered "doomed to extinction" for this reason, conservation efforts may not be pursued, Rojas-Bracho said.
Now, a team of scientists -- including Taylor and Rojas-Bracho -- have studied genetic patterns from vaquita tissue samples collected between 1985 and 2017 by Mexican researchers. Taylor is a senior scientist at the Oceanic and Atmospheric Administration's Southwest Fisheries Science Center in La Jolla, California, and Rojas-Bracho is a conservation biologist and member of the National Commission of Protected Areas in Mexico.
"Who would have thought that several decades later these same samples could tell us so much," said study coauthor Rojas-Bracho in a statement. "Genomics gives us clues into the species' past but also lets us peer into the future."
And it turns out that these little porpoises have enough resilience encoded in their genetics to recover if gillnetting is stopped. A study detailing the findings published Thursday in the journal Science.
"If we can allow these animals to survive, they can do the rest," said study coauthor Jacqueline Robinson, a postdoctoral researcher at the University of California, San Francisco, in a statement. "Genetically they still have the diversity that let them thrive for hundreds of thousands of years, until the gillnets arrived."
Small but thriving
The genetic information from the vaquitas show that they appeared about 2.5 million years ago and adapted to life in the shallow waters of the northern Gulf of California.
Over the past 250,000 years, the population has fluctuated from a few thousand to about 5,000 vaquitas -- which is rare when compared with other marine mammals. The fact that they have maintained a small population for so long has helped to reduce the risks of inbreeding because they have less genetic variation between them. A comprehensive survey of the population in 1997 showed there were 570 porpoises, but that number has declined greatly over the past 25 years.
Vaquitas also experience less harmful genetic mutation associated with small populations. When animals with negative genetic traits mate, it's more likely that their offspring will die.
In the case of this population, that actually helped to purge harmful traits from being spread across the vaquita population.