Only 10 of the world’s smallest marine mammals remain

The world’s smallest marine mammal is so critically endangered that only about 10 of them remain in their only habitat in the Gulf of California, Mexico.

But this does not necessarily mean that we are already facing the extinction of the vaquita porpoise, according to recent studies.

Sea vaquitas have almost become an endangered species due to illegal fishing with gillnets, which are used to catch shrimp and totoaba fish that share the same habitat as porpoises. Vaquitas, around 1.2 to 1.5 meters long, end up as “accompanying fauna” as they are not the intended target of nets.

The totoaba, a fish whose status is vulnerable on the International Union for Conservation of Nature’s Red List of Threatened Species, has a swim bladder that is highly prized in China and used for traditional medicine – and even regarded as a financial investment. Mexico has banned totoaba fishing and made it illegal to fish with gillnets where the vaquitas live, but the practice remains unchanged.

With such a small population, researchers have wondered whether vaquitas are at greater risk of extinction due to inbreeding.

Scientists Barbara Taylor and Lorenzo Rojas-Bracho, who have studied this risk for more than 20 years, published a 1999 paper suggesting that the “doomed hypothesis” of inbreeding could not be confirmed. This is important, because if an animal is deemed “doomed to extinction” for this reason, conservation efforts may not continue, Rojas-Bracho said.

Currently, there is a team of scientists – including Taylor and Rojas-Bracho – who have been studying genetic patterns from vaquita tissue samples collected between 1985 and 2017 by Mexican researchers. Taylor is a senior scientist in the Oceanic and Atmospheric Administration at the Southwest Fisheries Science Center in La Jolla, California, and Rojas-Bracho is a conservation biologist and member of the National Commission on Protected Areas in Mexico.

“Who would have thought that several decades later these same samples could tell us so much,” study co-author Rojas-Bracho said in a statement. “Genomics gives us clues about the species’ past, but it also allows us to analyze the future.”

And it turns out that these little porpoises have enough resilience encoded in their genetics to bounce back, if you can stop using the gillnet. A study detailing the results was published Thursday in the journal Science.

“If we allow these animals to survive, they can do the rest,” said study co-author Jacqueline Robinson, a postdoctoral researcher at the University of California, San Francisco, in a statement. “Genetically they still have the diversity that allowed them to thrive. for hundreds of thousands of years, until gill nets arrived.”

Small but prosperous

Genetic information on vaquitas reveals that this species emerged about 2.5 million years ago and adapted to life in the shallow waters of the Northern Gulf of California.

In the last 250,000 years, the population has fluctuated from a few thousand to around 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 to reduce the risks of inbreeding because they have less genetic variation between them. An exhaustive population study in 1997 revealed that there were 570 porpoises, but that number has greatly decreased over the last 25 years.

Vaquitas also undergo less harmful 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 actually helped to eliminate the harmful traits from propagating through the vaquita population.

Vaquitas are small and fast, so they rarely get photographed.

“They are essentially the marine equivalent of an island species,” Robinson said. “The fact that there were so few vaquitas allowed them to gradually eliminate highly harmful recessive genetic variants that could negatively affect their health in inbreeding.”

Variants rarely appear in larger populations of animals because two animals with these traits are more unlikely to interbreed and mate. But when a population rapidly declines, those odds increase and its descendants experience “consanguineous depression.” This weakens their health and can lead to the extinction of the species.

“A prevailing view in conservation biology and population genetics is that small populations can accumulate harmful mutations,” said Kirk Lohmueller, senior study author, associate professor of ecology and evolutionary biology and human genetics at the University of California, Los Angeles. Angeles.

“However, our finding that the vaquita likely has fewer highly harmful mutations lurking in the population means they are better prepared to survive future inbreeding, which is a good indication for their global recovery.”

how to save them

Gill nets pose the biggest threat because they cause porpoises to drown.

The researchers made simulations, based on the genetic information of the species to understand how best to protect them and calculate their risk of extinction in the next 50 years.

Immediately removing gillnets from their habitat would be the best bet for the animals’ survival. Unfortunately, even modest use of networks can decrease your chances of recovery. If the deaths of vaquitas as ‘accompanying fauna’ decrease by 80%, 62% of the population could still go extinct, according to the polls.

“The survival of individuals, and species, is in our hands. There is a high genetic probability that they can recover, if we protect them from the nets and allow the species to recover as quickly as possible to historic numbers”, said Phillip Morin, the The study’s author, a research molecular geneticist at NOAA Fisheries’ Southwest Fisheries Science Center, in a statement.

Surveys were also carried out to observe some of the few remaining vaquitas, and the researchers were pleased to see that they looked healthy and even had calves swimming with them, meaning they are actively breeding.

“This species has very little life left,” study co-author Christopher Kyriazis, a doctoral student in ecology and evolutionary biology at UCLA, said in a statement. “If we lose them, it will be the result of our human choices, not inherent genetic factors.”

Scientists continue to closely monitor vaquitas. The researchers believe that their approach to this study could be used to predict the risk of extinction of other endangered species, based on their genetics.

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