Population size

Given that the species wasn't described until 1958, comparison of the size of the original Vaquita population with the current population is basically impossible. Before 1986 only 20 sightings of Vaquita had been recorded, and many of these lacked sufficient details for confirmation.

Various independent censuses have been carried out. In 1976 Dr. Bernardo Villa, from the Instituto de Biologia of the Universidad Nacional Autonoma de México, estimated that there were between 200 and 300 individuals. From 1986 to 1989 Gregory Silber, of the University of California, Santa Cruz, conducted censuses by boat and airplane and reported 58 sightings of Vaquita, representing 110 individuals. From this study he estimated the population to be between 300 and 500 animals. In 1991 the scientific subcommittee on small cetaceans of the International Whaling Commission concluded that the population of Vaquita is very small, probably numbering in the low hundreds.

The latest census, done in 1997 by a team from the Universidad Autonoma de Baja California, the Instituto Nacional de la Pesca and the Center for Southwest Fisheries of the United States, derived a population estimate of 567 animals. This census used more precise methods for observing Vaquita, and more powerful binoculars and higher platforms on the boats than on previous censuses. Given these differences in methods, it is not possible to compare these numbers with those of earlier censuses. Nevertheless it is noteworthy that all censuses have estimated the population size at less than 1,000.

Reproduction and Natural History

Little is known about the age at which Vaquita reach sexual maturity, their longevity, their reproductive cycle or their population dynamics. Some estimates of these data have been made, however, based on stranded animals, animals tangled in nets and sightings at sea. Information obtained from other species of porpoises has also been used to try to understand the life cycle of vaquita. It is thought that Vaquita reach sexual maturity at around six years of age. The female has only one calf in the spring, probably every two years or more. The gestation period is around 11 months and it is believed that Vaquita live up to 22 years.