Few cetaceans are today free from the threat caused by human activity. The vaquita porpoise, Phocoena sinus , is one of the species in the most critical situation.
the smallest cetacean
Despite its name, the vaquita porpoise should not be confused with sea cows, the name given to manatees. The vaquita porpoise belongs to the zoological family of porpoises or Phocoenidae, which represent the smallest known cetaceans, and whose closest evolutionary relatives are belugas and narwhals. Among the porpoises, the vaquita is the only one that lives in warm waters. It does not usually exceed a meter and a half in length and barely reaches 50 kilos in weight.
How does the vaquita marina live?
The vaquita marina lives near the coast in the Gulf of California, Mexico . It does not usually move beyond 30 kilometers from the coast. It inhabits shallow areas, no more than 50 meters.
It usually swims alone or in small groups of two or three individuals , although groups of up to 10 individuals have been observed.
It lives in cloudy waters, which they themselves cause by stirring up the silt from the bottom. In these conditions, they take advantage of their highly developed sense of echolocation , to move without obstacles and hunt their prey, mainly fish, crustaceans and squid.
Calm in character, they swim slowly although they are capable of diving at high speed to disappear from the surface. They spend most of their time totally submerged , most only coming to the surface to breathe. They also tend to avoid boats.
critically endangered
Vaquitas are endemic to the northern quarter of the Gulf of California, in Mexico, extending over a territory of less than 2,000 square kilometers —some estimates indicate a total occupancy of less than 300.
The main threat facing vaquitas is fishing . Only during the year 1993, it is estimated that up to 15% of all those that existed at that time were captured. Since 1997, the regulation of fishing in the Gulf of California has been tightening, with repeated updates, aimed at protecting these small cetaceans. The latest regulations were promulgated in July 2021. But despite all of them, fishing continues in the area and fishing nets continue to be, even today, the greatest impact suffered by these animals.
Another impact to which the vaquitas are exposed is the ecological change suffered in the environment of the Gulf of California as a result of the drastic reduction in the flow of the Colorado River .
The historical average flow of this river was around 20.7 billion cubic meters per year, and with the water, all the nutrients that the river deposited in the gulf. However, the large number of reservoirs, dams and water transfers —which fed cities such as Las Vegas, Phoenix or San Diego—, added to anthropogenic climate change, which has increased the aridity of its basin, have reduced this contribution very significant. At the end of the 20th century, the average annual flow barely exceeded 5 billion cubic meters, and today it is estimated to be much lower.
The loss of flow of a large river implies, directly, a change in the amount of available nutrients, an alteration in the sedimentation processes, and a change in the salinity of the water. All this leads to serious ecological changes, which can be fatal for sensitive species, such as the vaquita porpoise.
Another problem the species faces is inbreeding . In fact, the analysis of the complete genome of the vaquita marina revealed that the low genetic diversity is not only due to its extreme scarcity of current population, but also because the only known population has less than 5,000 individuals from 300,000 years ago.
All these impacts have led this small porpoise to become the most endangered cetacean in the world . In 1997 a population of about 567 individuals was estimated. Eleven years later, it had dropped to 245. By 2015 it had dropped even further, with just 59 animals left alive.
The latest assessments carried out by the International Union for Conservation of Nature (IUCN) in March 2022, estimate its population at just 18 individuals . In few species are there such strong reasons to classify them as critically endangered species.
References:
Jaramillo-Legorreta, A. M. et al. 1999. A new abundance estimate for vaquitas: First step for recovery. Marine Mammal Science, 15(4), 957-973. DOI: 10.1111/j.1748-7692.1999.tb00872.x
Pazos, NER et al. 2011. Analysis of flow changes in the Colorado River due to climate change, and repercussions in the Mexicali Valley. XV International Congress of Project Engineering, 15.
Taylor, B. et al. 2022. Phocoena sinus. IUCN Red List of Threatened Species.
Taylor, B. L. et al. 2017. Extinction is Imminent for Mexico’s Endemic Porpoise Unless Fishery Bycatch is Eliminated: Mexican porpoise near extinction via gillnets. Conservation Letters, 10(5), 588-595. DOI: 10.1111/conl.12331
