Vaquita

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 ofthe number of individuals alive range from 100 ^[1] to 500 ^[2] making it amongst the most endangered of all marine mammals ^[1]. The word vaquita is Spanish for little cow.

Physical description

The Vaquita has a classic porpoise shape—stocky and curved into a concave shape when viewed from the side. It is thesmallest of the porpoises and thus amongst the smallest of all cetaceans . Individualsmay grow up to 150 cm in length and weigh up to 50 kilograms. They have a dark colouring around the eyes and mouth. Theupper side of the body is medium to dark grey. The underside is off-white to light grey but the demarcation between the sides isindistinct. The dorsal fin is in the centre of the back and larger than otherporpoise fins.

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 speciesendemic to the Gulf, the tototaba . CIRVA,the Committee for the Recovery of the Vaquita, concluded in 2000 that between 39 and 84 individuals are killed each year by suchgillnets. The Vaquita is listed by the IUCN and the Convention on InternationalTrade in the Endangered Species of Wild Fauna and Flora in the most critical category at risk of extinction. In order to tryto prevent extinction, the Mexican government has created a nature reserve covering theupper 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 thattrawlers be completely banned from the reserve area. Even if the number of Vaquita killed by fisheries is reduced to zeroconcerns remain amongst conservationists. Use of chlorinated pesticides, reduced flow of freshwater from the Colorado River dueto irrigation and depression due to interbreeding (see references) may also have a detrimental effect.

References

1. Whales, Dolphins and Porpoises, Carwardine, 1995, ISBN 0751327816
2. National Audubon Society: Guide to Marine Mammals of the World, Reeves et al 2002, ISBN 0375411410
3. 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
4. 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.