快猫短视频

An assessment of the world鈥檚 most endangered marine mammal, the vaquita, has found that there are at most 19 of the animals left alive in the wild.

Vaquitas are small porpoises that live only in a corner of the Gulf of California near Mexico. Their numbers have dwindled drastically over the past seven years, leaving them critically endangered. A report published in March concluded that there were just 10 of the animals left, but that may have been an underestimate.

Armando Jaramillo-Legorreta at the Ensenada Center for Scientific Research and Higher Education in Mexico and his colleagues analysed the data from a grid of 46 acoustic detectors placed in the vaquita refuge area in the upper Gulf of California to estimate how many of the animals are left.

Vaquitas聽make clicks to echolocate and communicate with one another in a nearly continuous stream. Jaramillo-Legorretta and his team measured the abundance of these clicks recorded by each sensor over 62 days in summer 2018, then figured out how many animals made them. They then compared this data to measurements made during the same 62-day periods in the years since 2011.

In 2015, these estimates put the vaquita population at 60. By the following year, it had halved to 30. By 2017, the number of vaquita clicks decreased by 62 per cent from the previous year, and by 2018, there was another 70 per cent decrease. Over the seven-year period studied, the vaquita population declined by 99 per cent.

Vaquitas are particularly threatened by fishing in their limited habitat. Vertically hung nets called gillnets are draped in the water to catch fish called totoaba, which are sought after because their swim bladders are used in Chinese medicine. The team found that even after a 2016聽ban on gillnet fishing, which isn鈥檛 uniformly enforced, the decline in vaquitas didn鈥檛 slow.

Recent research expeditions found two vaquita calves in 2018 and also determined that vaquitas can calve each year. This gives a sliver of hope for their survival, so long as gillnet fishing in the region can be curbed.