Sotalia fluviatilis
Vaquitas have the most restricted range of any marine cetacean;
they appear to live only in the northern end of the Gulf of
California. Most sightings of vaquita are in shallow (<40
m) water and within 25 km from the shore.
Very little is known about the natural history of vaquita,
and what is known is based on data collected from less than
50 individual animals. Vaquita appear to be the shortest porpoise,
growing to a maximum length of approximately 149 m. Female
vaquita appear to be larger than males, and reach sexual maturity
when they achieve a length of 1.35 m or so. The smallest measured
adult male vaquita was 1.28 m in length. It is believed that
females produce one calf annually, usually in late March or
early April. Vaquita feed primarily on teleost fishes that
are commonly found in the demersal and benthic zones of the
shallow waters of the upper Gulf of California. They also
appear to consume squids commonly found in that area.
Very little is known of the abundance of vaquita. The latest
abundance survey, jointly conducted in 1997 by the National
Fisheries Institute of Mexico and the US National Marine Fisheries
Service produced an estimate of 567 animals, with a 95% confidence
interval of between 177 and 1073 individuals. Vaquita are
currently listed in the IUCN Red List of Threatened Species
as Critically Endangered.
The greatest threat to the remaining vaquita is incidental
mortality in fishing gear. Vaquita are known to die in gillnets
set legally for sharks, rays, mackerels and chano. They are
also known to die frequently in illegal and occasionally permitted
gillnet sets for an endangered fish called totoaba. Vaquita
are also known to die in commercial shrimp trawls. Because
vaquita numbers are so low, any significant increases in annual
mortality, whether it be through human intereaction or through
rapid environmental perturbation, pose a serious threat to
this species
Vidal, O. et al. 1999. Vaquita. In S.H. Ridgeway & R.
Harrison [eds.], Handbook of Marine Mammals, Volume 6: The
Second Book of Dolphins and Porpoises. Academic Press. San
Diego.
Jefferson, T.A. et al. 1993. Marine Mammals of the World.
FAO Species Identification Guide. United Nations Environment
Programme. Rome.
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