The world’s most endangered porpoise is disappearing much faster than previously believed, according to a new report from the International Committee for the Recovery of the Vaquita.

Found only in the northern Gulf of California, the remaining 97 vaquitas are threatened by gill-net fishing. Despite an emergency two-year ban enacted by the Mexican government in April, fishermen still use the nets.

Recent data from acoustic monitoring show that the species is declining by an average of 31 percent a year — much higher than the previous estimate of 18.5 percent, which scientists said was the steepest decline of cetaceans on record.

The rapid loss of the species parallels local reports of increased illegal fishing for totoaba, which are prized in China for their swim bladders, used in food. Because vaquitas are about the same size, they are easily ensnared in nets meant for totoaba, and drown. More illegal fishing is occurring in the marine reserve set aside for the vaquita.