The Vaquita, the world's smallest cetacean, dives toward extinction

The Vaquita, the world's smallest cetacean, dives toward extinction
The culprit of the littlest porpoise's fate: accidental mortality as "bycatch" Rhett Butler, mongabay.com
December 10, 2006

Accidental death in fishing nets is driving the world's smallest cetacean, the Vaquita (Phocoena sinus), towards extinction, according to a new study published in the current issue of Mammal Review, the official scientific periodical of the Mammal Society.

The population of the Vaquita, a species of porpoise that measures less than 1.5 m (five feet) long and is endemic to the northwestern corner of the Gulf of California, is believed to be around 400 individuals, making it one of the two most critically endangered small cetaceans in the world. However, unlike whales and some other cetaceans that have been diminished by hunting or habitat degradation, the decline of the Vaquita is purely accidental. Its diminutive size and small range puts the species at particular risk to entanglement in gill nets set for fish and shrimp fishing. Estimates from the Committee for the Recovery of the Vaquita (CIRVA) suggest that 8-16 percent of Vaquitas may be lost annually as bycatch, indicating that the species could be extinct by 2050.

To stem its population decline, the Mexican government declared a Vaquita Refuge on December 29th, 2005 which bans trawling in about 80 percent of the Vaquita's limited range. The decree also set aside funds -- about $1 million -- to compensate fishermen affected by the ban. While these are positive steps, the authors of the paper say that the state governments of the Upper Gulf need to do more to support actions proposed by CIRVA, an international Vaquita recovery team. The governments are apparently hesitant to take further action until a second survey definitively shows continuing decline of the Vaquita population.

Courtesy of the Marine Mammal Commission
The elusive vaquita, first described only in 1958, is found in the shallow (less than 50 m deep), near shore (within 40 km) waters of the northern Gulf of California, Mexico.

The authors, which include Lorenzo Rojas-Bracho and Armando Jaramillo-Legorreta of the Marine Mammal Program at the National Institute of Ecology in Ensenada, and Randall Reeves of the Okapi Wildlife Associates in Quebec, Canada, argue that such a survey will be exceptionally costly -- $29M over 39 years -- and not particularly effective at saving the species from extinction. Instead, say the authors, "it is wiser to invest available funds in conservation actions, particularly in ones that offer viable socioeconomic alternatives to fishermen."

"The vaquita's survival does not depend on more or better science but on improved management," they write. "As a funding priority, implementation of conservation measures and evaluation of their effectiveness should come ahead of more surveys or improved estimation of by-catch."

Citations: ROJAS-BRACHO, LORENZO, REEVES, RANDALL R. & JARAMILLO-LEGORRETA, ARMANDO (2006). "Conservation of the vaquita Phocoena sinus." Mammal Review 36 (3), 179-216. doi: 10.1111/ j.1365-2907.2006.00088.x

This article is based on a news release from Blackwell Publishing Ltd.

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