Why is the vaquita on the brink of extinction?

Sixty-five years ago the vaquita was not even known to science. It was first described in 1958, from a few skulls found stranded near the Colorado delta in the Gulf of California. At the time its population was estimated at between five and ten thousand animals. Today this small porpoise, endemic to a restricted area in the northern Gulf of California, numbers fewer than ten surviving individuals. It is, beyond dispute, the most threatened marine mammal in the world. And its history is one of the most tragic in contemporary conservation: a species condemned not by hunting, nor by pollution, nor by climate change, but as collateral damage of another illegal trade, thousands of kilometres away.

A tiny and inconspicuous cetacean

The vaquita is above all a small animal: 1.40 metres long and 45 kilograms on average in adults. Females, slightly larger than males, can reach 1.50 metres. It is the smallest cetacean known. Its coloration is plain: slate grey above, whitish below, with black markings around the eyes and the mouth that give it a recognisable face.

Its habitat is restricted: an area of about four thousand square kilometres in the northern Gulf of California, between the towns of San Felipe and Puerto Peñasco. This area, where the water is turbid with sediment from the Colorado, is ironically also its ecological refuge: the poorly transparent water limits predation and allows the species to hunt by echolocation in a sheltered environment. Unfortunately it is also the exact area where the totoaba lives.

The vaquita is an extremely inconspicuous animal: it does not breach, it does not blow spectacularly, and it lives in very small groups (one to three individuals most of the time). The biologists who study it spend weeks at sea for only one or two sightings. That is partly why it was described so late, and why the decline was identified so late.

The collapse

The decline is exponential and catastrophic. In 1997 the first systematic estimate gave about 600 animals. In 2008, 245. In 2015, 60. In 2018, 19. In 2023, between 10 and 13. In 2024 the most recent acoustic surveys detected only a handful of animals, perhaps fewer than 10. The annual rate of decline lies between 30% and 50%, which puts the species on the brink of immediate extinction.

What makes the story particularly bitter is that the cause is perfectly identified and technically avoidable. It is neither a disease, nor climate change, nor competition with other species: it is one specific type of illegal fishing gear, the gillnet, targeting one particular fish, the totoaba.

The economic driver: the totoaba swim bladder

The totoaba (Totoaba macdonaldi) is a large fish of the sciaenid family, endemic to the Gulf of California. It can reach two metres and more than a hundred kilograms. Its dried swim bladder is regarded in China as a luxury food (“maw“) and as an ingredient of traditional medicine, held to improve the skin and the circulation. Demand is massive and opaque, mainly in Hong Kong and southern China.

The price is extravagant. A single dried totoaba swim bladder can fetch several tens of thousands of dollars on the black market. One successful catch can bring in the equivalent of a decade of legal fishing. With an economic incentive of that size in a poor region of Mexico, large-mesh gillnets, banned since 1975, are deployed on a massive scale. The vaquita, which shares both habitat and size with the totoaba, is caught alongside it and drowns within minutes.

The totoaba itself is protected: it has been listed in Appendix I of CITES since 1976, and trade in it is prohibited. But enforcement of that ban runs up against local corruption, economic pressure on fishing communities, and the complexity of the trafficking routes, which pass through the United States and sometimes across the Pacific to Hong Kong.

The attempts to save it

Several initiatives have been launched without lasting success. In 2015 Mexico banned the use of gillnets in the vaquita’s range and deployed the navy to enforce the ban. Poaching continued, sometimes more discreetly, sometimes with violence: armed clashes between poachers and patrols have been documented.

In 2017 the “Vaquita CPR” programme attempted to capture the last remaining animals for captive breeding. It was a desperate last resort. The outcome was tragic: the first female captured died of stress within hours. The programme was halted immediately. The species does not tolerate captivity.

Since then the NGO Sea Shepherd has patrolled the area and recovered ghost nets. The Mexican courts have increased penalties, and the Mexican navy maintains a deterrent presence. But poaching continues at a rate high enough to keep vaquita mortality above the species’ rate of reproduction.

A window opened by genetics

A paper by Jacqueline Robinson and her team, published in Science in 2022, brought a glimmer of technical hope. By sequencing the genomes of the surviving vaquitas and of older museum specimens, they showed that the population carries a surprisingly low load of deleterious mutations. Against expectation, the vaquita is not condemned by the genetic founder effect (the accumulation of harmful mutations in a small isolated population). If mortality in nets were to stop immediately, the population could in theory recover from about ten individuals.

The authors’ conclusion is at once luminous and terrible: the vaquita is not condemned biologically. It is condemned economically. Only an end to the illegal trade in totoaba swim bladders can save it. The window is very narrow, but it is still open.

Sources

• CIRVA, Comité Internacional para la Recuperación de la Vaquita, annual reports (1997-2024).
• Rojas-Bracho, L. & Reeves, R.R. (2013). “Vaquitas and gillnets: Mexico’s ultimate cetacean conservation challenge”. Endangered Species Research, 21.
• Robinson, J.A. et al. (2022). “The critically endangered vaquita is not doomed to extinction by inbreeding depression”. Science, 376.
• IUCN Red List, Phocoena sinus, Critically Endangered (2017+).
• Brownell, R.L. et al. (2019). “Vaquita extinction risk”. Conservation Letters.

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