for National Geographic News
The recently declared extinction of the Chinese river dolphin has focused attention on the plight of another imperiled marine mammal—the world's smallest porpoise.
Found only in waters off Mexico, the vaquita may now be the most endangered of any whale or dolphin species, due to the animal's frequent and fatal entanglements in fishing nets, experts say.
The International Committee for the Recovery of the Vaquita (CIRVA), a conservation research group, estimates only 250 to 400 of the elusive marine mammals remain.
Those numbers, if accurate, mean the vaquita is on a trajectory toward extinction. The last full survey, conducted in 1997, estimated its total population at 567.
The animals remain highly threatened by fishing and shrimp harvesting in the region, according to an overview of the species' status published this summer in the quarterly journal Mammal Review.
The study, led by Lorenzo Rojas Bracho of Mexico's National Institute of Ecology in Ensenada, notes that the vaquita's actual numbers are uncertain. The animal is notoriously difficult to detect and observe, making an accurate census nearly impossible.
But between 39 and 78 vaquitas are killed each year due to entrapment in fishing nets, Rojas Bracho said.
That number exceeds the estimated number of yearly births, providing the basis for the team's lowered population estimate.
A new survey being conducted by Rojas Bracho and colleagues largely agrees with the CIRVA estimate.
"Our results point to a 30 percent population reduction [since 1997]," Rojas Bracho said.
The Price of Fish
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