Ken Norris commented how he discovered this species: "it was a spring day in 1950. I had one more dune to check, one just north of Punta San Felipe. As I walked the dune margin I saw a whitened skull partly protruding from the sand, buried just above the reach of the usual high tide. I couldn't identify it, except to say that it was obviously a very small porpoise or dolphin. On April 28, 1955 Ken mentions in his field notes that our way back we spotted porpoises, which I think are an undescribed species. I suspect they are the harbor porpoise, Phocoena, but of an unknown species." He was correct. With two other skulls available to Norris, all collected in San Felipe, Baja California, he and William N. McFarland described in 1958 a new species of harbor porpoise of the genus Phocoena in the Gulf of California.
: Odontoceti (unranked)
Size, shape and distinctive characteristics
The maximum length for females is 150 cm while males are slightly smaller, 145 cm. and weight is about 50 Kg. The vaquita is similar in external morphology to the harbor porpoise (Phocoena phocoena), its geographically nearest phocoenoid neighbor. However, the vaquita differs from the harbor porpoise and the other phocoenids in total length (the vaquita is smaller); the vaquita's flippers are proportionately larger; and the vaquita's dorsal fin is taller and more falcate.
The vaquita is robust in build. In profile, the head appears as a truncated cone with the posterior part of the melon (forehead) sloping inward, toward the blowhole. Anteriorly, the melon slopes abruptly to the snout tip. Generally, the pigmentation pattern is a dark gray cape, pale gray lateral field, and white ventral field. The most conspicuous features of the pigmentation are the relatively large black eye and lip patches.
Vaquitas occur mainly north of 30º45'N and west of 114º20'W. The vaquita has the smallest geographical range of any marine mammal. Its 'core area' consists of about 2235 km2 centred at Rocas Consag, some 40 km east of the town of San Felipe, Baja California. Nearly the entire population lives within a 4000 sq-km (1519 sq-mile) area. The range of the vaquita coincides with most of the Upper Gulf of California and Delta of the Colorado River Biosphere Reserve There is no evidence to indicate that the vaquita's overall range has changed in historic times.
Ecology and Behaviour
Little is known about vaquita's ecology and behavior. Vaquitas occur in small groups of 1-3 individuals; often just a mother and calf pair. They are typically inconspicuous at the surface (they rarely splash, jump or leap) and they avoid boats. These behaviors, coupled with their small body size, and murky waters of their habitat, make them difficult to observe unless sighting conditions are ideal.
Vaquita's habitat has been described as an area of high concentrations of nutrients and high abundance of phytoplankton and zooplankton in the estuary and adjacent waters of the Upper Gulf of California which maintains a rich marine ecosystem with a diverse and abundant fauna, including seabirds and marine mammals.
Vaquitas are versatile, none-selective predators. Many prey species, such as croakers and toadfish, produce sound; vaquitas may use passive listening to locate prey.
Vaquitas live for approximately 20 years and breed for the first time between the ages of three and six. Breeding is seasonal, with most calves produced in March and April; few females appear to breed each year. Nothing is known of their mating system, although the large size of testes (almost 3% of body mass), reverse sexual dimorphism (females are bigger than males) and small group sizes that sperm competition plays an important role in the species' reproductive strategy.
Vaquitas are generalist feeders, consuming a wide variety of over 21 benthic and demersal (bottom-dwelling) teleost fishes and squids. However there are three main prey species utilized by vaquita: corvine (Isopisthus altipinnis); midshipman toadfish (Porichthys mimeticus), and squid (Lolliguncula panamensis). Because of the small sample size for studies it has not been demonstrated with certainty any differences in diets in relation to sexes or age classes. None of the primary prey of the vaquita is commercially important species, although some are taken as by-catch in shrimp trawl fisheries.
Historical abundance of the vaquita is unknown, but genetic evidence indicates that the population was never large. The most precise estimate of abundance was obtained from a cooperative Mexican-American survey conducted in 1997 that sampled the entire geographical range of the species and estimated there were 567 individuals (95% CI 177-1073).
The most recent estimate based on simultaneous visual and acoustic data gives a total vaquita abundance in 2008 was estimated to be 245 animals (CV=73%, 95%CI 68-884). The 2008 estimate was 57% lower than the 1997 estimate, an average rate of decline of 7.6%/year.
The vaquita qualifies for listing as Critically Endangered based on criteria A4d and C2a(ii).
A4d: Given what is known about fishing history in the northern Gulf of California and the vaquita's vulnerability to entanglement in gillnets, it is reasonable to assume that the porpoise population has been declining since the 1940s when gillnet fisheries became widespread in the region. The best estimate of total population size is from 1997: 567 (95% CI 177 - 1,073) (Jaramillo-Legorreta et al. 1999). The estimated annual level of mortality in the early 1990s for one of the three main fishing communities, based on reports from onboard observers (Method 1) and those observer reports combined with information from interviews with fishermen (Method 2), was 84 (95% CI: 14, 155).
The generation time for the vaquita is estimated as 10 years (Rojas-Bracho and Taylor, 1999; Taylor and Rojas-Bracho, 1999), therefore 3 generations is approximately 30 y
Incidental mortality in gillnets for fish and shrimp represents the greatest immediate threat to the survival of the species (bycatch). The only quantitative estimates of bycatch are from 1993-95 and refer to only one of the three main fishing ports: at least 39 individuals were killed per year (95% CI 14-93) using combined data from observers and interviews with fishermen. Assuming that boats from the other ports may experience similar bycatch rates, the total of annual removals is likely well above what would be sustainable. The International Committee for the Recovery of Vaquita (CIRVA) recommended, among several other recommendations, that bycatch of vaquitas must be reduced to zero as soon as possible to prevent its extinction. These conclusions have been repeatedly confirmed and reiterated by the Society for Marine Mammalogy and the Scientific Committee of the International Whaling Commission (IWC).
Of all risk factors - which include the potential for disturbance by trawling to affect the foraging, reproductive, and aggregating behaviour of vaquitas and the non-specific implications of ecological change as a result of diverting the Colorado River for urban and agricultural use and hence the loss of freshwater input to the northern Gulf - bycatch as mentioned above is unequivocally the immediate concern for this species, while the others are less well characterised and longer-term.
In 2007 Mexico's President announced the Conservation Program for Endangered Species (PROCER), which required specific Species Conservation Action Programs (PACE) for selected species. The vaquita topped the list of only five species. PACE-Vaquita, the first of its kind to be presented, is Mexico's conservation policy strategy to put into practice CIRVA's recommendations.
The central goal is to eliminate vaquita bycatch. Given that fishing is one of the most-important economic activities in the Upper Gulf of California, PACE-Vaquita has designed mechanisms to remove the fishing gear that has threatened the vaquita by:
(1) Enforcing the existing bans on gillnet fishing in the Biosphere Reserve and Refuge Area, and possibly expanding the ban to a larger protected area;
(2) Encouraging alternative methods of fishing that do not catch vaquitas; and
(3) Providing economic compensation to fishermen, including a buyout plan and assistance with starting alternative businesses.
So far the following results have been achieved:
(1) The Vaquita Refuge free of entangling and gillnets and shrimp trawlers;(2) 230 artisanal fishing boats withdrawn from fishing activities; and (3) 105 artisanal fishing boats are participating in the fishing gear replacement program.
With this program 602 fewer artisanal boats will be using gillnets. Enforcement is an important component of the recovery program. PROFEPA, the environmental watchdog of SEMARNAT, with the support of the Navy.
CIRVA (Comite Internacional Para la Recuperacion de la Vaquita/International Committee for the Recovery of the Vaquita). Scientific Reports of: First Meeting, 25-26 January 1997; Second Meeting, 7-11 February 1999; Third Meeting, 18-24 January 2004. Available at http://swfsc.noaa.gov/prd-vaquita.aspx.
D'Agrosa, C., Lennert-Cody, C.E. & Vidal, O. 2000. Vaquita bycatch in Mexico's artisanal gillnet fisheries: driving a small population to extinction. Conservation Biology 14: 1110-1119.
Hohn, A. A., A. J. Read, S. Fernandez, O. Vidal and L. T. Findley. 1996. Life history of the vaquita, Phocoena sinus (Phocoenidae, Cetacea). Journal of Zoology, London 239: 235-251
Jaramillo-Legoretta, A.M., Rojas-Bracho, L. and Gerrodette, T. 1999. A new abundance estimate for vaquitas: first step for recovery. Marine Mammal Science 15: 957-973.
Jaramillo-Legoretta et al., A.M., Rojas-Bracho, L., Brownell, R.L., Jr., Read, A.J., Reeves, R.R., Ralls, K. and Taylor, B.L. 2007. Saving the vaquita: immediate action not more data. Conservation Biology 21: 1653-1655.
Norris, K.S. & McFarland, W.N. 1958. A new harbor porpoise of the genus Phocoena from the Gulf of Califonria. Journal of Mammalogy 39: 22-39.
Rojas-Bracho, L. and B. Taylor. 1999. Risk factors in the vaquita. Marine Mammal Science 15 (4): 974-989.
Rojas-Bracho, Reeves, R.R. and Jaramillo-Legoretta, A. 2006. Conservation of the vaquita Phocoena sinus. Mammal Review 36: 179-216.