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Overview
Brief Summary
Biology
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Comprehensive Description
Description
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Distribution
Range Description
Endemic to upper quarter of Gulf of California, extent of occurrence (EOO) >2,000 km², area of occupancy (AOO) (core area) approx. 2,000 km².
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Geographic Range
The range of Phocoena sinus is extremely restricted. This species of porpoise is found only in the northern end of the Gulf of California. Phocoena sinus (commonly known as the vaquita) are found only in shallow water, close to shore.
Biogeographic Regions: pacific ocean (Native )
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Distribution
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Range
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Physical Description
Morphology
Physical Description
Adult vaquitas are typically 1.2 to 1.5m in length with females being slightly larger than males. At birth their average length is 0.6-0.7m. Juveniles also have white spots on their dorsal fins.
Phocoena sinus has between 34-40 teeth which are unicuspid, or "acorn like" (Silber, 1990) and a blunted rostral profile. P. sinus 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--the slender body increases surface area/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 (Hohn et al., 1996).
Range mass: 30 to 55 kg.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
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Ecology
Habitat
Habitat and Ecology
Systems
- Marine
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Habitat
An interesting feature of the vaquita is that it is the only species of porpoise that is found in such warm waters. Most phocoenids are restricted to water cooler than 20 degrees Celsius, vaquitas are unique in their ability to tolerate large annual fluctuations in temperature (Hohn, et al, 1996). The Gulf of California may experience temperature ranges from 14 degrees C in January to 36 degrees C in August. This may have an effect on the reproductive seasonality of this species.
Aquatic Biomes: coastal
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Habitat
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Environmental ranges
Depth range (m): 0 - 0
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Habitat
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Trophic Strategy
Food Habits
Vaquitas feed on teleost fishes and squid, which are found near the surface of the water. In several individuals the remains of Guld croakers were found.
Animal Foods: fish; mollusks
Primary Diet: carnivore (Piscivore )
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Life History and Behavior
Reproduction
Reproduction
Vaquitas are usually solitary. This would indicate a social system in which sperm competition is extremely important (Hohn et al., 1996). Within such systems, males attempt to maximize their fitness not by monopolizing access to females, but rather by mating with as many females as possible. As would be expected in multi-male breeding systems, male vaquitas have relatively large testes size in comparison to their body size.
Mating System: polygynous
Sexual maturity is believed to be reached between the ages of three and six years. Body mass may help to distinguish mature from immature specimens for both males and females (Hohn et al., 1996). Vaquitas have highly seasonal reproduction. During the spring there is a complete lack of larger calves. The mating period is from mid-April to May, with a gestation period of roughly 10.6 months. Births occur at the beginning of the following March. P. sinus have non-annual ovulation, thus they do not produce calves each year (Hohn et al., 1996). Females have one calf per pregnancy and lactate for less than one year.
Breeding season: The mating period is from mid-April to May
Average number of offspring: 1.
Average gestation period: 10.6 months.
Range weaning age: 12 (high) months.
Average weaning age: 12 months.
Range age at sexual or reproductive maturity (female): 3 to 6 years.
Range age at sexual or reproductive maturity (male): 3 to 6 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Contributor/s
Justification
The generation time for the vaquita is estimated as 10 years (Rojas-Bracho and Taylor 1999, Taylor and Rojas-Bracho 1999), therefore three generations is approximately 30 years.
Criterion 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) (Method 1) or 39 (95% CI: 14, 93) (Method 2) (Rojas-Bracho and Taylor 1999, D?Agrosa et al. 2000). Using the 1997 abundance estimate, the range of bycatch estimates for a single community in the early 1990s, and plausible potential rates of population increase for phocoenids, Rojas-Bracho and Taylor (1999) estimated that the vaquita population was declining rapidly, possibly by as much as 15% per year. Using the lower of their plausible decline rates (0.05), the population size would be reduced by more than 80% over three generations (i.e., 30 years), including both the past and the future (Rojas-Bracho and Taylor 1999). The cause of the reduction (incidental mortality in fisheries) has not ceased and may even have increased over the last 10 years based on fishing effort (ca. 1,000 gillnet boats might operate in vaquita habitat each year; Rojas-Bracho et al. 2006).
Criterion C2a(ii): The mature and reproductively active component of the census population is estimated as 0.55 (Woodley and Read 1991), or 311 in 1997. Given the inferred decline in abundance due to fishery bycatch during the nine years since 1997 (possibly at a rate of 0.05 to 0.15/yr according to Taylor and Rojas-Bracho 1999), there are now plausibly far fewer than 250 mature individuals (criterion C). From available data on fishery activities (types and effort) and vaquita bycatch rate, a continuing decline in number of mature individuals is projected and inferred (C2). It is assumed that the species population is not divided into subpopulations and therefore 100% of mature individuals are in a single population (C2aii).
History
- 2007Critically Endangered
- 1996Critically Endangered
- 1994Endangered(Groombridge 1994)
- 1990Endangered(IUCN 1990)
- 1988Vulnerable(IUCN Conservation Monitoring Centre 1988)
- 1986Vulnerable(IUCN Conservation Monitoring Centre 1986)
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Conservation Status
Vaquita are listed as critically endangered. They are perhaps the most endangered of the cetaceans with only a few hundred remaining. Phocoena sinus are often caught in fishing nets which are set to catch other marine animals, most often shrimp. This species becomes entangled either in the shrimp nets or within gillnet fisheries for sharks. It is estimated that 25-30 individuals drown each year as a result. To further complicate the situation, relatively few individuals reach maturity because of the high mortality of young individuals (they are highly susceptible to being netted), and the remaining older individuals are approaching the upper limit of their lifespan so as to be contributing little to future reproduction (Hohn et al, 1996).
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: critically endangered
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Status: Endangered
Date Listed: 01/09/1985
Lead Region: Foreign (Region 10)
Where Listed:
Population detail:
Population location: entire
Listing status: E
For most current information and documents related to the conservation status and management of Phocoena sinus , see its USFWS Species Profile
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Status
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Trends
Population
There is no immediate means of estimating trend, so it is necessary to impute the direction and rate of population change by reference to a population model laden with assumptions.
Naturally rare (Taylor and Rojas-Bracho 1999) and very difficult to detect and count (cryptic) (Gerrodette et al. 1995). No population subdivision is known or suspected, i.e. no subpopulations, but also no fragmentation. Most recent estimate of total population size (1997 shipboard line transect survey): 567 (95% CI 177 to 1,073) (Jaramillo-Legorreta et al. 1999).
Given the difficulty of sampling the vaquita population, generation time and percent mature (i.e., capable of reproduction) can only be estimated crudely and by analogy with the life history and population biology of the better-studied harbour porpoise (Phocoena phocoena). Thus reasonable default values for porpoises (phocoenids) would be 10 years and 55%, respectively.
Ongoing decline inferred from available information on abundance and bycatch rate. Even an unrealistically optimistic scenario - high end of 95% CI for population size (1,073), lower of two estimates of annual bycatch mortality for a single fishing port (39 porpoises) - indicates likely decline (Rojas-Bracho and Taylor 1999).
Population Trend
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Threats
Threats
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Threats
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Management
Conservation Actions
An International Committee for the Recovery of the Vaquita (CIRVA) was established in 1997 and has developed recommendations including: immediate prohibition of large-mesh gillnets throughout the species' known range, followed in sequence by bans on medium- and small-mesh gillnets; exclusion of gillnets and trawls within an enlarged biosphere reserve; and improved enforcement of fishing regulations in the northern Gulf generally. Considerable attention has also been given to development of less harmful fishing methods, alternative income-generating activities for fishing communities, and community-based education and awareness (Rojas-Bracho et al. 2006).
On 29 December 2005 the Mexican Ministry of Environment declared a Vaquita Refuge that contains within its borders approximately 80% of all verified vaquita sighting positions. In the same decree, the State Governments of Sonora and Baja California were offered $(US)1 million to compensate affected fishermen. The results of this action cannot yet be evaluated.
It is listed on CITES Appendix I.
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Conservation
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Relevance to Humans and Ecosystems
Benefits
Economic Importance for Humans: Negative
P. sinus may interfere with human activity is in that it may inadvertantly become entangled in fishing nets set for shrimp, sharks, and totoabo causing a nuisance and possibly reducing catch during one net hauling.
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Economic Importance for Humans: Positive
This species is not used directly by humans. It is interesting in the sense that it is a unique phocoenid morphologically and behaviorally. The fact that it is limited in its range and is extremely endangered should encourage study of the vaquita.
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Risks
IUCN Red List Category
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IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=125373
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Wikipedia
Vaquita
The vaquita (Phocoena sinus) is a rare species of porpoise. It is endemic to the northern part of the Gulf of California. Estimates of the number of individuals alive range from 100 [2][3] to 300.[3] The word "vaquita" is Spanish for little cow.[4] Since the baiji (Lipotes vexillifer) is believed to have gone extinct in 2006,[5] the vaquita has taken on the title of the most endangered cetacean in the world.[6]
Other names include Cochito, Gulf of California Harbor Porpoise, Gulf of California Porpoise, Gulf Porpoise, Hafenschweinswal, and Marsouin du Golfe de Californie.[citation needed]
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Biology
Physical description
The Vaquita has a classic porpoise shape (stocky and curved into a star shape when viewed from the side). It is the smallest of the porpoises, a group of marine mammals that differ from dolphins in their stockier, robust body, lack of an elongated beak, and their distinctively shaped teeth.[7] Individuals may reach a mature size of 1.2-1.5 m (4-5 ft) and may weigh 40-55 kg (90-120 lb).[4] They have large black eye rings and lip patches. 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 flippers are proportionately larger than in other porpoises and the fin is taller and more falcate. The skull is smaller and the rostrum is shorter and broader than in other members of the genus.
Habitat
The habitat of the vaquita is thought to be restricted to the northern area of the Gulf of California.[4] The vaquita lives in shallow, murky lagoons along the shoreline and is rarely seen in water much deeper than 30 meters; indeed, it can survive in lagoons so shallow that its back protrudes above the surface. The vaquita is most often sighted in water 11 to 50 metres deep, 11 to 25 kilometres from the coast, over silt and clay bottoms. Its habitat is characterised by turbid water with a high nutrient content.[7] Other characteristics of its habitat are strong tidal mixing, convection processes and high primary and secondary productivity.
Behavior
There are very few records of the Vaquita in the wild. It appears to swim and feed in a leisurely manner, but is elusive and will avoid boats of any kind. It rises to breathe with a slow, forward-rolling movement that barely disturbs the surface of the water, and then disappears quickly, often for a long time. It has an indistinct blow, but makes a loud, sharp, puffing sound reminiscent of the Harbour Porpoise.
Schooling
Like other phocoenids, the vaquita occurs singly or in small groups, usually from 1 - 3 individuals but as many as 8 - 10.
Diet
All of the 17 fish species found in vaquita stomachs can be classified as demersal and or benthic species inhabiting relatively shallow water in the upper Gulf of California, and it appears that the vaquita is a rather non-selective feeder on small fishes and squids in this zone. Like other cetaceans, the vaquita produces high-frequency clicks which are used in echolocation. This may be used to locate their prey, but several of the fish species it feeds on are known to produce sound and so it is possible that the vaquita locates them by following their sound, rather than by echolocating.[7]
Reproduction
Most calving apparently occurs in the spring. Gestation is probably 10–11 months. Maximum observed life span was 21 years.
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. Estimates have placed the vaquita population at 567 in 1997 and 150 in 2007.[4] The decline in the vaquita population is believed to be due to the animals becoming trapped in gillnets intended for capturing another species endemic to the Gulf, the totoaba. 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 inbreeding[8] may also have a detrimental effect.
The Vaquita is one of the top 100 EDGE Species, meaning "Evolutionarily Distinct, Globally Endangered". Evolutionarily distinct animals have no close relatives and represent proportionally more of the tree of life than other species, meaning they are top priority for conservation campaigns.
On October 28, 2008, Canada, Mexico, and the United States, under the jurisdiction of the NAFTA environmental organization, the Commission for Environmental Cooperation, launched the North American Conservation Action Plan (NACAP) for the Vaquita.[9] The NACAP is a strategy to support Mexico’s efforts to recover the Vaquita, which is considered the world’s most-endangered marine mammal. The U.S. government has listed the vaquita as endangered under the Endangered Species Act.
See also
References
This article incorporates text from the ARKive fact-file "Vaquita" under the Creative Commons Attribution-ShareAlike 3.0 Unported License and the GFDL.
- ^ Rojas-Bracho, L., Reeves, R.R., Jaramillo-Legorreta, A. & Taylor, B.L. (2008). Phocoena sinus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 march 2009. Database entry includes justification for why this species is critically endangered
- ^ Whales, Dolphins and Porpoises, Carwardine, 1995, ISBN 0-7513-2781-6
- ^ a b Aquarium Passport Book, Aquarium of the Pacific 2005
- ^ a b c d "Vaquita (Phocoena sinus)". Encyclopedia of Endangered Species. Volume 1. Gale. 1 February 2009. Retrieved 2 November 2011.
- ^ Turvey, S.T.; Pitman, R.L., Taylor, B.L., Barlow, J., Akamatsu, T., Barrett, L.A., Zhao, X., Reeves, R.R., Stewart, B.S., Wang, K., Wei, Z., Zhang, X., Pusser, L.T., Richlen, M., Brandon, J.R. and Wang, D. (2007). "First human-caused extinction of a cetacean species?". Biology Letters 3: 537–540. doi:10.1098/rsbl.2007.0292. PMC 2391192. PMID 17686754. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2391192.
- ^ Jaramillo-Legorreta, A.; Rojas-Bracho, L., Brownell Jr, R.L., Read, A.J., Reeves, R.R., Ralls, K. and Taylor, B.L. (2007). "Saving the vaquita: immediate action, not more data.". Conservation Biology 21 (6): 1653–1655.
- ^ a b c Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (2002). Encyclopedia of Marine Mammals. London: Academic Press.
- ^ 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.
- ^ "Project Summary". Commission for Environmental Cooperation. 2011. http://www.cec.org/Page.asp?PageID=122&ContentID=1256&SiteNodeID=244&BL_ExpandID=. Retrieved 5 November 2011.
- General references
- 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
- National Audubon Society: Guide to Marine Mammals of the World, Reeves et al. 2002, ISBN 0-375-41141-0
- Convention on Migratory Species
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