Vaquita (Phocoena sinus)

With adults reaching about 1.5 meters, or about 5 feet in length, and weighing 55 kilograms, the vaquita is among the smallest cetaceans in the world and is the smallest member of its genus, Phocoena. As with other porpoises, the vaquita is small but robust.

There is reverse sexual dimorphism in the vaquita, as females are larger than males.

The vaquita has between 34-40 teeth which are unicuspid, or acorn-like, and a blunted rostral profile.

Vaquita are physically similar to the harbor porpoise (Phocoena phocoena) in many ways with an exception being that the vaquita is more slender. This has been explained in terms of their warmer habitat as the slender body increases surface area and volume ratio, thus increasing heat dissipation in a warm environment. This explanation has also been used to explain the occurrence of larger appendages within this species.

The life span of the vaquita is expected to be similar to that of the harbor porpoise, approximately 20 years. Both mature early, 3 years for harbor porpoise, likely close to 3 but potentially up to 6 years for the vaquita. The oldest vaquita, as of 2008, was estimated to be 21 years of age.

The generation time for the vaquita is estimated as 10 years, therefore three generations is approximately 30 years.

SEXUAL DIMORPHISM

Larger Females

BODY LENGTH

1.49-2 m. / 4.9-6.6 ft.

BODY MASS

29-55 kg. / 65-120 lb.

LIFESPAN

20-21 yr.

GENERATION LENGTH

10 yr.

Although the vaquita was not scientifically described until 1958 by Norris & McFarland, fishermen in the upper Gulf of California were familiar with the porpoise long before scientists were aware of its existence.

The vaquita first became known to the scientific community after the discovery of a bleached skull on the beach north of Punta San Felipe in Baja California Norte, Mexico on March 18th, 1950. The following year, two additional skulls were found and these three skull specimens formed the basis for the naming and description of a new species of porpoise, Phocoena sinus.

The vaquita’s specific name sinus was suggested to Norris and Mc-Farland by Carl L. Hubbs in 1958, but full descriptions of the vaquita’s external morphology were not available until 1987.

Genetic and morphological data suggest that vaquita are most closely related to porpoises in South America. Genetic data suggest divergence from two sister taxa, Burmeister’s porpoise (Phocoena spinipinnis) and spectacled porpoise (Australophocaena dioptrica) in the Pleistocene (at least 2.5 million years ago).

The vaquita is believed to represent a relict population of an ancestral species, most clearly related to Burmeister’s porpoise, that crossed the equator from the Southern Hemisphere during a period of Pleistocene cooling. Genetic analyses have corroborated this interpretation. Affinities of the axial skeleton and external morphometry suggest that Phocoena sinus evolved from a Pleistocene stock of Burmeister’s porpoise.

KINGDOM

Animalia

PHYLUM

Chordata

CLASS

Mammalia

ORDER

Cetartiodactyla

FAMILY

Phocoenidae

GENUS

Phocoena

SPECIES

sinus

SUBSPECIES

None

The vaquita, or vaquita marina, is known by several different names, such as cochito, Gulf of California harbour porpois”, Gulf of California porpoise, or simply Gulf porpoise.

The most commonly used name for this porpoise is vaquita which translates to little cow in Spanish.

The vaquita’s specific name is Phocoena sinus. Sinus was suggested to Norris and Mc-Farland by Carl L. Hubbs and is Latin, meaning bay, referring to the occurrence of the species in the Gulf of California.

Porpoise literally means pig-fish from the Old French porpais (porc meaning pig or swine, and peis translating to fish), probably a translation of Germanic words such as the Old Norse mar-svin, meaning mereswine, which was also an early English word for porpoises or small dolphins.

ALTERNATE

Cochito, Desert Porpoise, Gulf Porpoise, Gulf of California Porpoise, Gulf of California Harbour Porpoise, Vaquita Marina, Vaquita Porpoise

GROUP

Crowd, Herd, Pod, School, Shoal

MALE

Bull

FEMALE

Cow

YOUNG

Calf

The vaquita has the smallest geographical range of any marine mammal.

Nearly the entire population lives within a 4,000 square kilometer (1,519 square mile) area, an area less than ¼ the size of metropolitan Los Angeles.

The vaquita is known to occur only in the extreme northern Gulf of California, Mexico, mainly north of 30° 45’N and west of 114°20’W.

The core area of the vaquita distribution consists of about 2,500 square kilometers and is centered around Rocas Consag (31°18’N, 114° 25′ W), 40 kilometers northeast of the town of San Felipe, Baja California.

The range of the vaquita coincides with most of the Upper Gulf of California and Delta of the Colorado River Biosphere Reserve, one of the earth’s most extraordinary marine habitats supporting a diversity of macro-invertebrates, fish, birds, marine reptiles and marine mammals.

There is no evidence to indicate that the vaquita’s overall range has changed in historic times.

EXTANT

Mexico

The vaquita is a marine species that lives in a relatively shallow, turbid, and dynamic marine neritic and marine oceanic environments.

The vaquita is typically found in pelagic and epipelagic waters less than 50 meters deep.

MARINE NERITIC

Pelagic

MARINE OCEANIC

Epipelagic

Vaquita usually occur in small groups of one to three individuals; often just a mother and calf pair. Vaquita have been observed singly and in small groups of up to eight or ten individuals, but many such groups can be loosely aggregated over several square kilometers.

Vaquita are shy and hard to find. Their elusive behavior, coupled with their small body size, make them difficult to observe.

Vaquita are typically inconspicuous at the surface as they avoid boats and rarely splash, jump, or leap.

CIRCADIAN RHYTHM

Diurnal

MOVEMENT PATTERN

Non-Migrant

Stomach contents from entangled vaquita have been examined for prey species identification. The 19 species of prey identified primarily represented demersal and benthic fish and squids. Epipelagic and demersal fish were found in stomachs from ten vaquitas. Squid was also found, but considered to be secondary.

Stomachs from another 24 vaquitas contained primarily two species of endemic fish, a silver weakfish (Isopisthus altipinnis) and a mimetic midshipman (Porichthys mimeticus), and one of two species of small squids.

Bronze-striped grunt (Orthopristis reddingi) and the Ronco croaker (Bairdiella icistia) have also been found in the stomachs of a few decomposed vaquita found beach-cast.

PREFERENCE

Generalist

STYLE

Forager

Although the mating system and social structure of the vaquita have not been studied, it has been inferred from the large testes size, (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.

Unlike most other porpoise species which breed every year, vaquitas give birth every 2 years.

The maximum population growth rate of the vaquita is not likely to exceed 4% annually, a rate commonly used for porpoises.

Most births occur in early March, presumably following a peak in ovulations and conceptions in approximately mid-April. The gestation is estimated to be 11 months.

The sexual maturity of the vaquita is expected to be similar to that of the harbor porpoise (Phocoena phocoena). Both mature early, 3 years for harbor porpoise, likely close to 3 but potentially up to 6 years for the vaquita.

BREEDING SEASON

April-May

BREEDING INTERVAL

2 Years

PARENTAL INVESTMENT

Maternal

GESTATION

10.5-11 Months

BIRTHING SEASON

March

LITTER

1

WEANING

1 Year

SEXUAL MATURITY

3-6 Years

Potential predators of vaquitas are large sharks, killer whales (Orcinus orca), and man.

The vaquita and the totoaba (Totoaba macdonaldi), a large, long-lived fish species in the croaker family (Scianidae), have much in common. Both the vaquita and the totoaba are critically endangered, protected from international trade under CITES, and are both endemic to a relatively small area of the Upper Gulf of California, Mexico. They are of a similar size, have a similar lifespan, and both species are threatened with extinction by the same activity – illegal fishing.

Because the swim bladders of the totoaba are highly sought in Hong Kong and southern mainland China, there has been a resurgence of illegal fishery. Dubbed aquatic cocaine due to the high prices it fetches, the demand for dried totoaba swim bladders is threatening not just the totoaba but also the vaquita, which is accidentally caught and drowned in the illegal nets set for totoaba.

While documented mortality of the vaquita in gillnet fisheries has been occurring since at least the 1950s, researchers noted that the vaquita has probably been incidentally caught since the 1930s.

Vaquitas have probably always been rare.

Historical abundance of the vaquita is unknown, but genetic evidence indicates that the population was never large. Judging by the results of simulations of plausible population dynamics, their loss of genomic variability likely occurred over evolutionary time. No polymorphism has been found in the mitochondrial DNA control region and in the DQB locus of the Major Histocompatibility Complex, (MHC,) and limited diversity was found in the DRB locus of the HMC, of 43, 25 and 29 vaquita specimens, respectively. These findings are consistent with the hypothesis that the evolutionary history of the species included a bottleneck or founder event and that its extreme loss of genomic variability occurred over evolutionary time rather than being caused by human activities.

According to results from an acoustic monitoring program, there are 18 vaquita individuals left in the wild.

The most precise estimate of abundance was obtained from a cooperative Mexican-American shipboard line transect survey conducted in 1997 that estimated there were 567 individuals. An estimate in 2007 that was based on the 1997 population size, natural birth and death rates, and continued rates of bycatch, (lethal entanglement,) suggested that only about 150 individuals remained, only a portion of which were mature and contributing to recovery through reproduction. The 2008 population size was as low as 125 individuals. By 2014, it had plummeted to just 97 animals due to fishery bycatch.

According to results from acoustic monitoring of vaquita echo-location clicks, the vaquita’s population is declining rapidly, with a decline of nearly 50% since 2015, 42% between 2013 and 2014, and 8.7% per year from 1997 to 2007.

MATURE INDIVIDUALS

18

FRAGMENTATION

Not Fragmented

Potential vaquita threats that have been suggested, but appear not to be significant risk factors at present, include inbreeding, depression, and pesticide exposure.

Other less well-characterized and longer-term risk factors include the potential for disturbance by trawling to affect vaquita behavior and the uncertain effects of ecological changes from dam construction on the Colorado River and the resultant loss of freshwater input to the upper Gulf. The last of these may be important in the long term and deserves investigation, however, entanglement is the clearest and most immediate concern.

Mortality in gillnets has long been recognized as the most serious and immediate threat to the vaquita’s survival. Gill nets of various mesh size for fish and shrimp cause incidental mortality (bycatch) of vaquitas. The only available estimates of the vaquita bycatch rate are 39 (using one method) and 84 (using a different method) animals killed per year by boats from a single port. This alone would represent 7 or 15%, respectively, of the estimated total population size.

CIRVA, (Comité Internacional para la Recuperación de la Vaquita,) predicts that the vaquita could be extinct unless fishery bycatch is eliminated immediately. CIRVA recommends that the Government of Mexico enact emergency regulations to establish a gillnet exclusion zone. Vaquita will surely go extinct if nothing changes.

BIOLOGICAL RESOURCE USE

Fishing & Harvesting Aquatic Resources

NATURAL SYSTEM MODIFICATIONS

Dams & Water Management/Use

POLLUTION

Domestic & Urban Waste Water, Industrial & Military Effluents, Agricultural & Forestry Effluents

Most biological and ecological information of the vaquita is unknown, but knowledge of vaquita biology is emerging largely due to the retrieval of carcasses from entangled animals.

Vaquita conservation management and action has been largely ineffective at controlling vaquita mortality in gillnets. Until recently, measures to address the primary vaquita threat of bycatch have been inadequate, incomplete or not enforced.

Early efforts include the creation of the Upper Gulf of California and Colorado River Delta Biosphere Reserve in 1993 and the Refuge Area for the Protection of the Vaquita in 2005. Gillnet fishing in the Refuge Area was officially prohibited, but there was little enforcement as the refuge did not cover the entire vaquita range and the ban was widely ignored. Gillnet fishing continued unimpeded; the number of pangas (traditional fishing boats) doubled from 2005-2007, and illegal fishers outnumbered legal fishers.

Over the past five years the Government of Mexico has increased efforts to protect the vaquita, investing more than $30 million in conservation efforts including a compensation scheme (‘rent-out’, ‘buy-out’, and ‘switch-out’) to eliminate gillnetting and industrial trawling within the Refuge, but the vaquita continued to decline.

The US and Mexican Navies, as well as scientists in both countries, plan to deploy a squadron of highly trained, bomb-locating bottlenose dolphins to search out their tiny, highly endangered relatives, the vaquitas, in an effort to conserve the last of the rapidly disappearing porpoises. The dolphins usually use sonar for missions of hunting down underwater mines or warding off enemy swimmers. The plans are to use the bottlenose dolphins to locate and capture a few vaquitas, and transport them to a safe location. If the captured vaquitas were then to breed, that would be ideal. The team just hopes to keep a few vaquitas alive and safe until the region is free from illegal fishing.