Credit: © Dr Armando Jaramillo-Legorreta

The vaquita porpoise, one of the world's most endangered animals, could become extinct within a year if fishing nets continue being used illegally, a university in Scotland warned on Wednesday.

Numbers of the , which only lives in the upper Gulf of California in Mexico, may now have dropped to fewer than 10, according to research by the University of St Andrews published in Royal Society Open Science.

The dolphinlike vaquita ("small cow" in Spanish) is the world's smallest cetacean, with females measuring 55 inches (140 centimeters) and males 53 inches (135 centimeters) on average. The vaquitas, which are gray or white, have a tall dorsal fin and long flippers.

The global vaquita population was estimated at 30 in 2016, the University of St Andrews said.

Gillnets—nets that hang vertically and catch fish by their gills—kill vaquitas as a bycatch.

The nets are used by fishermen to capture totoabas, another . The swim bladder of the totoaba is believed by the Chinese to have medicinal and aphrodisiac properties.

Totoaba fishing is illegal and Mexico has also banned the gillnet, but unlawful fishing has nevertheless continued.

"The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved," said Professor Len Thomas, director of the university's Centre for Research into Ecological and Environmental Modelling.

Studying recordings of echolocation clicks by the vaquita, which are made via a large grid of acoustic sensors spread out over the water the mammals inhabit, allowed researchers to estimate the decline of the species.

Numbers of the vaquita declined by nearly 99 percent since the current monitoring study began in 2011, and by almost 50 percent annually since 2016.

The vaquita's long reproduction cycle means it is unable to multiply quickly.

More information: Armando M. Jaramillo-Legorreta et al. Decline towards extinction of Mexico's vaquita porpoise ( Phocoena sinus ), Royal Society Open Science (2019). DOI: 10.1098/rsos.190598

Journal information: Royal Society Open Science