They close fishing areas in the habitat of the vaquita marina 1:06
(CNN) --
The world's smallest marine mammal is so threatened that only about 10 individuals remain in its only habitat, Mexico's Gulf of California.
However, according to new research, this may not spell the end for the vaquita, a species of porpoise.
Vaquitas have been pushed to the brink of extinction due to illegal gillnet fishing, which is used to catch shrimp and totoaba that share the same habitat as porpoises.
The vaquitas, which are between 1.2 and 1.5 meters long, end up being "bycatch" since they are not the target of the nets.
The totoaba fish, classified as vulnerable on the Red List of Threatened Species of the International Union for Conservation of Nature, has a swim bladder that is highly valued in China and used for traditional medicine.
It is even considered as a financial investment.
Mexico has banned totoaba fishing and made gillnet fishing illegal in places where vaquitas live, but the practice continues unabated.
Vaquita porpoises are small and fast, so they are rarely caught on camera.
With such a small population, researchers have wondered if vaquitas are at greater risk of extinction due to inbreeding.
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Scientists Barbara Taylor and Lorenzo Rojas-Bracho, who have been studying this risk for more than 20 years, published a paper in 1999 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 the genetic patterns of 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 for Protected Areas in Mexico.
"Who would have thought that several decades later these same samples could tell us so much," Rojas-Bracho, a co-author of the study, said in a statement.
"Genomics gives us clues about the past of the species, but it also allows us to peek into the future."
And it turns out that these little porpoises have enough resilience encoded in their genetics to bounce back if gillnet fishing stops.
A study detailing the findings was published Thursday in the journal
Science.
"If we allow these animals to survive, they can do the rest," study co-author Jacqueline Robinson, a postdoctoral researcher at the University of California, San Francisco, said in a statement.
"Genetically they still have the diversity that allowed them to thrive for hundreds of thousands of years, until gillnets came along."
Vaquita genetic information shows that they appeared about 2.5 million years ago and adapted to life in the shallow waters of the northern Gulf of California.
Small but prosperous
Over the last 250,000 years, the population has fluctuated from a few thousand to about 5,000 vaquitas, which is rare when compared to other marine mammals.
The fact that they have kept a small population for so long has helped reduce the risks of inbreeding because they have less genetic variation between them.
A comprehensive survey of the population in 1997 showed that there were 570 porpoises, but that number has greatly decreased in the last 25 years.
Vaquitas also experience fewer deleterious genetic mutations associated with small populations.
When animals with negative genetic traits mate, their offspring are more likely to die.
In the case of this population, this helped prevent harmful traits from spreading throughout the vaquita population.
A vaquita porpoise (right) and her calf (left) in the waters off San Felipe, Baja California, Mexico.
"They are essentially the marine equivalent of an island species," Robinson said.
"The low natural abundance of vaquitas has allowed them to gradually purge highly deleterious recessive genetic variants that could negatively affect their health if inbred."
Variants rarely appear in larger animal populations because two animals with these traits are more unlikely to meet and mate.
But when a population shrinks rapidly, those odds increase and their offspring experience "inbreeding depression."
This weakens their health and can send a species spiraling towards extinction.
"A prevailing view in conservation biology and population genetics is that small populations can accumulate deleterious mutations," said lead study author Kirk Lohmueller, an associate professor of ecology and evolutionary biology and of human genetics at the University of California, Los Angeles, in a statement.
"However, our finding that vaquita probably have fewer strongly deleterious mutations hidden in the population means they are better suited to survive future inbreeding, which bodes well for their overall recovery."
How to save vaquitas
Gillnets are the biggest threat because they cause porpoises to drown.
The researchers ran simulations, based on the vaquitas' genetic information, to see which scenario worked best to protect them and calculate their risk of extinction in the next 50 years.
Immediate removal of gillnets from their habitat was the vaquitas' best bet for survival.
Unfortunately, even modest use of gillnets could reduce your chances of recovery.
According to the study, if vaquita deaths as a result of bycatch decrease by 80%, 62% of the population could still go extinct.
"The survival of individuals, and of the species, is in our hands. There is a high genetic probability that they can recover, if we protect them from gillnets and allow the species to recover as soon as possible until reaching historical numbers. Phillip Morin, a co-author of the study and a molecular genetics researcher at NOAA's Southwest Fisheries Science Center, said in a statement.
Studies were also done to look at some of the few remaining vaquitas, and the researchers were pleased to see that they appeared healthy and even had calves swimming with them, meaning they are actively reproducing.
"Vaquitas have very little time left," study co-author Christopher Kyriazis, a UCLA doctoral student in ecology and evolutionary biology, said in a statement.
"If we lose them, it will be the result of our human decisions, not inherent genetic factors."
Scientists continue to actively monitor vaquitas.
The researchers believe their approach in this study could be used to predict the extinction risk of other endangered species based on their genetics.
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