Vaquita
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| Phocoena sinus Norris & McFarland, 1958 |
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 Vaquita range
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The vaquita (Phocoena sinus) is a rare species of porpoise. It is endemic to the northern part of the Gulf of California (Sea of Cortez). Estimates of the number of individuals alive range from 100 [2][3] to 300 [3]. With the recent functionally extinct declaration of the Baiji (Yangtze River Dolphin), it is now the world's most endangered cetacean.[2] The word "vaquita" is Spanish for little cow.
Other names include Cochito, Gulf of California Harbor Porpoise, Gulf of California Porpoise, Gulf Porpoise, Hafenschweinswal, and Marsouin du Golfe de Californie.
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[edit] Physical description
The Vaquita has a classic porpoise shape (stocky and curved into a concave shape when viewed from the side). It is the smallest of the porpoises and thus amongst the smallest of all cetaceans. Individuals may grow up to 150 centimetres (4.92 ft) in length and weigh up to 50 kilograms (110.2 lb). They have large black eye rings and lip patches. The upper side of the body is medium to dark grey. The underside is off-white to light grey but the demarcation between the sides is indistinct. The flippers are proportionately larger than in other phocoenids and the fin is taller and more falcate. The skull is smaller and the rostrum is shorter and broader than in other members of the genus.
[edit] Habitat
The vaquita lives in shallow, murky lagoons along the shoreline and is rarely seen in water much deeper than 30 meters; indeed, it can survive in lagoons so shallow that its back protrudes above the surface. Other characteristics of its habitat are strong tidal mixing, convection processes and high primary and secondary productivity.
[edit] Behaviour
There are very few records of the Vaquita in the wild. It appears to swim and feed in a leisurely manner, but is elusive and will avoid boats of any kind. It rises to breathe with a slow, forward-rolling movement that barely disturbs the surface of the water, and then disappears quickly, often for a long time. It has an indistinct blow, but makes a loud, sharp, puffing sound reminiscent of the Harbour Porpoise.
[edit] Food
All of the 17 fish species found in vaquita stomachs can be classified as demersal and or benthic species inhabiting relatively shallow water in the upper Gulf of California, and it appears that the vaquita is a rather non-selective feeder on small fishes and squids in this zone.
[edit] Schooling
Like other phocoenids, the Vaquita occurs singly or in small groups, usually from 1 - 3 individuals but as many as 8 - 10.
[edit] Reproduction
Most calving apparently occurs in the spring. Gestation is probably 10-11 months. Maximum observed life span was 21 years.
[edit] Conservation
Vaquita have never been hunted directly. Indeed their continued existence was only confirmed by a dedicated survey in 1985. However it is known that the Vaquita population is declining, and that this is due to animals becoming trapped in gillnets intended for capturing another species endemic to the Gulf, the totoaba. CIRVA, the Committee for the Recovery of the Vaquita, concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. The Vaquita is listed by the IUCN and the Convention on International Trade in the Endangered Species of Wild Fauna and Flora in the most critical category at risk of extinction. In order to try to prevent extinction, the Mexican government has created a nature reserve covering the upper part of the Gulf of California and the Colorado River delta. CIRVA is recommending that this reserve be extended southwards to cover the full known area of the Vaquita's range and that trawlers be completely banned from the reserve area. Even if the number of Vaquita killed by fisheries is reduced to zero, concerns remain amongst conservationists. Use of chlorinated pesticides, reduced flow of freshwater from the Colorado River due to irrigation, and depression due to inbreeding[4] may also have a detrimental effect.
The Vaquita is one of the top 100 EDGE Species, meaning "Evolutionarily Distinct, Globally Endangered". Evolutionarily distinct animals have no close relatives and represent proportionally more of the tree of life than other species, meaning they are top priority for conservation campaigns.
[edit] References
- ^ Rojas-Bracho, L., Reeves, R.R., Jaramillo-Legorreta, A. & Taylor, B.L. (2007). Phocoena sinus. 2007 IUCN Red List of Threatened Species. IUCN 2007. Retrieved on 2007-09-13. Database entry includes justification for why this species is critically endangered
- ^ a b Whales, Dolphins and Porpoises, Carwardine, 1995, ISBN 0-7513-2781-6
- ^ a b Aquarium Passport Book, Aquarium of the Pacific 2005
- ^ Examining the risk of inbreeding depression in a naturally rare cetacean, the Vaquita, Taylor and Rojas-Bracho, Marine Mammal Science Vol 15. Pages 1004-1028.
- General references
- Preventing the extinction of a small population: Vaquita fishery mortality and mitigation strategies D'Agrosa, Lennert and Vidal. Conservational Biology vol 14. pages 1110-1119
- National Audubon Society: Guide to Marine Mammals of the World, Reeves et al 2002, ISBN 0-375-41141-0
- Convention on Migratory Species
[edit] External links
- Conservation of the vaquita, (2006), Rojas-Bracho et al, Mammal Review, 36:3, Pg 179. On-line at Blackwell Synergy - Retrieved July 22, 2007
- Evolutionarily Distinct and Globally Endangered species: [1]
- Whale & Dolphin Conservation Society (WDCS)
- Vaquita.org
