MEXICO CITY — The world’s smallest porpoise, the vaquita, is slipping closer to extinction despite the Mexican Navy’s efforts to protect it and its habitat from illegal fishing, experts have warned.

Only about 60 of the snub-nosed vaquitas are left in the northern reaches of the Gulf of California, said a panel of scientists that tracks threats to the marine mammal’s survival and recommends measures to save it.

“We are watching this precious native species disappear before our eyes,” Lorenzo Rojas-Bracho, the chairman of the panel, said in a statement issued by the group on Friday.

Demand for an organ from a large endangered fish called the totoaba, which swims in the same area, is driving the vaquita’s disappearance. The totoaba’s swim bladder is dried, smuggled across the border to California and then shipped to China, where it is considered a delicacy and sells for as much as $10,000 per kilogram, or close to $5,000 a pound.