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 to 500 making it amongst the most endangered of all marine mammals. 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 the smallest of the porpoises and thus
amongst the smallest of all cetaceans. Individuals may grow up to 150 cm in
length and weigh up to 50 kilograms. They have a dark colouring around the
eyes and mouth. 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 dorsal fin is in the centre of the back and larger than other porpoise
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 species endemic 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 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 interbreeding (see references) may also have a detrimental effect.
References:
Whales, Dolphins and Porpoises, Carwardine, 1995.
National Audubon Society: Guide to Marine Mammals of the World, Reeves et al 2002.
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.
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.
