Vaquita
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Classification:
Population mondiale
Description Et Histoire Naturelle
Physical DescriptionAlthough the terms "porpoise" and "dolphin" are often used interchangeably, porpoises (Family: Phocoenidae) differ from dolphins (Family: Delphinidae) in a number of ways. Porpoises are smaller, rarely exceeding two meters (6.6 feet) in length; porpoises tend to be more robust than dolphins; the dorsal fins of porpoises are usually smaller and more triangular; and porpoises usually lack the "beak" of the dolphin.
The vaquita is a porpoise and is known to some as the cochito or the Gulf of California harbor porpoise. Very little is known about this species which was first described by scientists in 1958. Since that time, vaquitas have only been seen alive by a handful of scientists and what is known is based on data from only 50 individuals.
Like other porpoises, vaquitas are stocky, with a blunt head and no beak. Vaquitas are grayish on the back, fading to white on the belly. They have dark eye rings, lip patches and flipper stripes, a tall dorsal fin and large, pointed flippers. Calves tend to be darker than adults. The maximum length of an adult is close to 1.49 meters (4.9 feet); females are thought to be larger than males.
Natural History
Most porpoise species are shy and are not as
exuberant on the water's surface as dolphins. Vaquitas are no exception. Because
they only inhabit coastal waters in the northern quarter of the Gulf of
California, Mexico, they have the most restricted range of any marine cetacean.
Females are thought to produce one calf annually in late March or early April.
Adults feed primarily on teleost (bony) fishes and may consume squid as
well.
The latest abundance survey, from 1997, produced an estimate of 567
animals (95 percent confidence interval of between 177 and 1,073
animals).
Situation De L'Espèce
StatusThe vaquita is listed as Endangered under the U.S. Endangered Species Act (ESA) and Critically Endangered by the International Union for the Conservation of Nature and Natural Resources (IUCN). It is listed on Appendix I of the Convention on the Trade in Endangered Species of Fauna and Flora (CITES).
Threats to the Species
The vaquita is the most endangered porpoise in
the world and is in imminent danger of extinction. At least 30 - 40 are killed
annually in fishing nets for totoaba, sea bass, rays and sharks; some die each
year in shrimp trawls as well.
International Trade
Listed on
CITES Appendix I which prohibits international
trade.
Auteur Et Sources
Sources
CITES. 2001. Phocoena sinus. http://www.cites.org
IMMA. 2001. Vaquita. www.phocoena.org
IUCN. 2001. The 2000 IUCN Red List of Threatened Species — Phocoena sinus. http://www.redlist.org
Jefferson, T.A., S. Leatherwood and M.A. Webber. 1993. Marine Mammals of the World. FAO Species Identification Guide. United Nations Environment Programme. Rome.
Leatherwood, S and R.R. Reeves. 1983. The Sierra Club Handbook of Whales and Dolphins. Sierra Club Books, San Francisco. 302pp.
Read, A. 1999. Porpoises. WorldLife Library. Voyageur Press. 72pp.
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.
