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How acoustic monitoring gave us a last chance to save the vaquita

  • Monitoring the vaquita’s vocalizations has allowed scientists to closely and accurately monitor the species’ unfortunate decline.
  • Illegal fishing for totoaba is the biggest threat to the vaquita. They are killed as bycatch, drowning in nets meant for the fish.
  • Conservationists say the next step is to capture vaquitas for captivity, a highly controversial plan with major risks.

Thanks to a five-year acoustic monitoring program, conservationists have detected the rapid decline of the vaquita before it is too late – giving them one last shot to save the species. By monitoring the vaquita’s clicking vocalizations, a new paper in Conservation Biology announced that the population of the vaquita has dropped to fewer than 30 animals. Until recently the exact population size was unknown, hindering conservation efforts and further risking the species’ survival.

The size of a large dog, the vaquita (Phocoena sinus) is the world’s most endangered porpoise. Unlike most cetaceans, its range is restricted to a small northern portion of the Gulf of California. Only discovered in 1958, the vaquita was already considered Vulnerable on the IUCN Red List by 1986. Today it is Critically Endangered.

Beginning in 2011, the Acoustic Monitoring Program is an international collaborative effort between scientists from NOAA’s Southwest Fisheries Science Center and Mexico’s National Institute of Ecology and Climate Change. Since the project commenced, scientists estimate the total vaquita population has declined a staggering 90 percent, taking the global population down from an already troublingly low 200 individuals to less than 30.

While researchers knew the vaquita was critically endangered, they were not expecting to document anything like this.

“The [Acoustic Monitoring Program] was designed to detect the anticipated recovery of vaquitas. Instead we documented the consequence of the rise of the illegal [totoaba] fishery,” Dr. Barbara Taylor, lead author of the study, said.

An acoustic monitoring program has revealed that there are fewer than 30 vaquitas left in the wild. Photo by Paula Olson, NOAA.

The totoaba (Totoaba macdonaldi) is a fish roughly the size of a vaquita that is prized for its swim bladder in China. The illegal trade is so lucrative that a single swim bladder can fetch up to $5,000 on the black market. Unfortunately, the gillnets used to capture these fish are the perfect size to ensnare and kill vaquitas, and the secretive nature of the enterprise has made it impossible to measure the extent to which vaquitas are caught as bycatch.

While the Mexican government declared a fishing ban inside the Gulf of California’s Vaquita Refuge in 2008, the illegal toataba fishery has only continued to expand.

Until the results of the monitoring program were released, scientists were unsure about the impact of this secretive illegal fishery within the refuge.

“[I had thought that] our ability to monitor vaquitas was so poor that they were likely to go extinct before we could prove they were declining,” said Taylor. “Fortunately, acoustic methods changed all that.”

Unlike visual surveys or estimating population decline from bycatch, passive acoustic monitoring does not require scientists to see the notoriously shy vaquita to know they are there. Instead, the researchers, led by Dr. Jaramillo-Legoretta, deployed 48 acoustic detectors in the Vaquita Refuge over a five-year period. These detectors pick up the vaquitas’ echolocation clicks, allowing researchers to develop a population estimate based on the total number of clicks per 24-hour period. In order to ensure that seasonal or tidal variations did not compromise the data, researchers deployed detectors 24 hours a day during the same three-month period each year.

Preliminary results released in 2014 led to a two-year gillnet ban throughout the vaquita’s entire range. Updated results released in 2016 led to the launch of an emergency action plan called VaquitaCPR just last month. According the plan, researchers will locate and capture a number of vaquitas using Navy trained dolphins under the leadership of Mexico’s Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT).

This solution of holding vaquitas in temporary captivity for safekeeping is not without controversy. Vaquitas have never been successfully kept in captivity before, let alone successfully bred. And cetaceans are notoriously difficult to keep alive in captivity. Some scientists argue that this plan could wind up killing the very vaquitas it sets out to protect. However, conservationists are running out of options.

“Given the rapid and continuing decline, saving at least some vaquitas is a wise conservation course recommended by the recovery team,” said Taylor. She stressed that it is a temporary fix. Long-term actions that protect vaquitas in their natural environment, including a permanent gillnet ban and development of alternative fishing gear, will still take top priority.

The vaquita Acoustic Monitoring Program proves that continuously monitoring endangered species is critically important. Without such measures, scientists might not notice unexpected or unseen threats until it is too late to save the species. In the case of the vaquita, there is still a very real risk of extinction – but without acoustic monitoring, that risk could have been an inevitability.


Jaramillo‐Legorreta, A., Cardenas‐Hinojosa, G., Nieto‐Garcia, E., Rojas‐Bracho, L., Ver Hoef, J., Moore, J., Tregenze, N., Barlow, J., Gerrodette, T., Thomas, L., & Taylor, B. (2016). Passive acoustic monitoring of the decline of Mexico’s critically endangered vaquita. Conservation Biology. doi: 10.1111/cobi.12789


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