It could be just days or weeks until the world's smallest porpoise becomes extinct, experts have warned.
The Vaquita species was only discovered in 1958, but within a few decades numbers have hit critical levels.
"We are down to 6-19 individuals remaining, by now these numbers have probably halved," Professor Len Thomas, a statistician at the University of St Andrews, wrote in the British journal Royal Society Open Science.
"We are in the final few days or months for this species."
The plight of the rare mammal has been tracked extensively, and since 2011 researchers have reported a 98.6% drop in numbers.
The porpoise only lives in a small area within the Gulf of California. It has already been classified as critically endangered by the International Union for Conservation of Nature.
Part of the risk to the species is accidental entanglement in illegal gillnets used by fishermen.
One in five Vaquita drown in the nets used to catch Totoaba fish, which are also endangered.
Thought by some to have fertility and rejuvenating properties, their bladders are sold as a delicacy in China - attracting up to $80,000 per kilogram, rivalling the cost of gold.
In 2016, ex-US president Barack Obama and former Mexican leader Enrique Pena Nieto introduced collaborative measures to protect the mammal.
The Mexican government banned fishing of the species and paid $74m to compensate fishers. The country's navy patrols the waters to prevent gillnet fishing.
US Navy dolphins have been enlisted to locate the so-called "ghost nets", allowing safe removal from the waters.
Professor Len Thomas said that the last seen Vaquitas were "healthy and calving and the real risk today is fishing".
He said: "The ghost nets are out there now and may kill more Vaquita.
"We need effective enforcement of the laws now, right now, it is critical."
Research published earlier this year gave fresh hope to those trying to save the porpoise. It showed females probably calve annually and not every 2-3 years as previously thought.
The Vaquita measures around four to five feet long and weighs in at just 120 pounds.
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