Vaquita

Vaquita
Size compared to an average human
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Phocoenidae
Genus: Phocoena
Species: P. sinus
Binomial name
Phocoena sinus
Norris & McFarland, 1958
Vaquita range

The vaquita (Phocoena sinus) is a rare species of porpoise endemic to the northern part of the Gulf of California. Since the baiji (Lipotes vexillifer) is believed to have gone extinct by 2006,[2] the vaquita has taken on the title of the most endangered cetacean in the world.[3] It is listed as critically endangered because the estimated number of individuals dropped below 100 in 2014, putting it in imminent danger of extinction.[4][5] That number was updated to approximately 60 in May 2016, leading to the conclusion that the species is headed for extinction within 5 years unless further conservation efforts are undertaken.[6]

The word vaquita is Spanish for "little cow". Other names include cochito, desert porpoise, vaquita porpoise, Gulf of California harbor porpoise, Gulf of California porpoise, and gulf porpoise.

Description

Vaquitas are the smallest and most endangered species of the cetacean order and are endemic to the northern end of the Gulf of California. The vaquita is somewhat stocky and has a classic porpoise shape. The species is distinguishable by the dark rings surrounding their eyes, patches on their lips, and a line that extends from their dorsal fins to their mouths. Their backs are a dark grey that fades to white undersides. As vaquitas mature, the shades of grey lighten. [7] Female vaquitas tend to grow to be a bit larger than the male.[7] Females usually end up at a length of 140.6 cm (55.4 in), compared to the males at 134.9 cm (53.1 in). The lifespan, pattern of growth, seasonal reproduction, and testes size of the vaquita are all similar to that of the harbour porpoise.[8] The flippers are proportionately larger than other porpoises, and the fin is taller and more falcated. The skull is smaller and the rostrum is shorter and broader than in other members of the genus.

Behavior

Vaquitas use high-pitched sounds to communicate with one another and for echolocation to navigate through their habitats. They generally seem to feed and swim at a leisurely pace. Vaquitas avoid boats and are very evasive. They rise to breathe with a slow, forward motion and then disappear quickly. This lack of activity at the surface makes them difficult to observe.[9] Vaquitas are usually alone unless they are accompanied by a calf,[10] meaning they are less social than other dolphin species. They may also be more competitive during mating season.[11] They are the only species belonging to the porpoise family that live in warm waters.[12] Vaquitas are nonselective predators.[13]

Schooling

Like other Phocoena, vaquitas are usually seen singly. If they are seen together, it is usually in small groups of two or three individuals.[7] Less often, groups around ten have been observed, with the most ever seen at once being 40 individuals.

Diet

Vaquitas tend to forage near lagoons.[7] 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. Vaquitas appear to be rather nonselective feeders on small fish and squid in this area. Some of the most common prey are teleosts (fish with bony skeletons) such as grunts, croakers, and sea trout.[14] Like other cetaceans, vaquitas may use echolocation to locate prey. They possibly locate their prey by following the sounds of prey movement.[1]

Life cycle and reproduction

A pair of vaquitas swims together.

Little is known about the lifecycle of vaquitas. Age at sexual maturity, longevity, reproductive cycle and population dynamics estimates have been made, but further research is needed. Most of these estimates come from vaquitas that have been stranded or caught in nets. Some are based on other porpoise species similar to vaquitas.

Vaquitas are estimated to live about 20 years in ideal conditions.[15][16] They mature sexually at 1.3 m long, as early as 3, but more likely at 6 years old. Reproduction occurs during late spring or early summer. Their gestation period is between 10 and 11 months. They have seasonal reproduction, and usually have one calf in March. The interbirth period, or elapsed time between offspring birth, is between 1 and 2 years. The young are then nursed for about 6 to 8 months until they are capable of fending for themselves.[17]

Distribution and habitat

The habitat of the vaquita is restricted to the northern area of the Gulf of California, or Sea of Cortez.[18] They live in shallow, murky lagoons along shorelines. They rarely swim deeper than 30 m (100 ft) and are known to survive in lagoons so shallow that their backs protrude above the surface. The vaquita is most often sighted in water 11 to 50 m (36 to 160 ft) deep, 11 to 25 km (6.8 to 16 mi) from the coast, over silt and clay bottoms. They tend to choose habitats with turbid waters, because they have high nutrient content,[1] which is important because it attracts the small fish, squid, and crustaceans on which they feed. They are able to withstand the significant temperature fluctuations characteristic of shallow, turbid waters and lagoons.

Conservation

The vaquita is considered the most endangered of 129 extant marine mammal species.[19] It has been classified as one of the top 100 evolutionary distinct and globally endangered (EDGE) mammals in the world.[7] The vaquita is an evolutionarily distinct animal and has no close relatives. These animals represent more, proportionally, of the tree of life than other species, meaning they are top priority for conservation campaigns. The EDGE of Existence Programme is a conservation effort that attempts to help conserve endangered animals that represent large portions of their evolutionary trees. The U.S. government has listed the vaquita as endangered under the Endangered Species Act. It is also listed by the IUCN and the CITES in the category at most critical risk of extinction.

Population decline

A vaquita swims in the foreground while fishing boats ply their trade in the distance.

Vaquitas have never been hunted directly, but their population is declining, largely due to animals becoming trapped in illegal gillnets intended for capturing the totoaba, a large critically endangered fish of the drum family endemic to the Gulf. A trade in totoaba swim bladders has arisen, driven by demand from China (where they are used in soup, being considered a delicacy and also thought to have medicinal value), which is greatly exacerbating the problem.[4][5]

Estimates placed the vaquita population at 567 in 1997.[18] Estimates in the 2000s ranged between 150[20][21] to 300.[21]

With their population dropping as low as 85 individuals in 2014,[22] inbreeding depression has probably begun to affect the fitness of the species, potentially contributing to the population's further decline.[23]

In 2014, estimates of the species' abundance dropped below 100 individuals.[4] An international vaquita recovery team concluded that the population is decreasing at a rate of 18.5% per year, and "the species will soon be extinct unless drastic steps are taken immediately."[5] Their report recommended that a ban on gillnet fishing be enforced throughout the range of the vaquita, that action be taken to eliminate the illegal fishery for the totoaba, and that with help from the U.S. and China, trade in totoaba swim bladders be halted.[4][5]

On 16 April 2015, Enrique Peña Nieto, President of Mexico, announced a program to conserve and protect the vaquita and the similar-sized totoaba, including a two-year ban on gillnet fishing in the area, patrols by the Mexican Navy and financial support to fishermen impacted by the plan.[24][25] However, some commentators believe the measures fall short of what is needed to ensure the species' survival.[26]

In early May 2016, the IUCN SSC – Cetacean Specialist Group reported that the vaquita population had dipped to around 60 remaining individuals. This represents a 92% decline from the 1997 population level. In March 2016 alone, at least three vaquitas drowned after being entangled in gillnets set for totoaba.[6] The report concluded that the gillnet ban would need to be extended indefinitely, with more effective enforcement, if the vaquita is to have any chance of long term survival. Otherwise, the species is likely to become extinct within 5 years.[6]

Primary threats

Vaquitas have dark eye rings

Studies performed in El Golfo de Santa Clara, one of the three major ports in which vaquitas live, indicated that gillnet fishing causes about 39 vaquita deaths a year. This is close to 17% of the whole vaquita population within this port. While these results were not taken from the entire range of habitat in which vaquitas live, it is reasonable to assume that these results can be applied to the whole vaquita population, and in fact may even be a little low.[27] Even with a gillnet ban throughout the vaquita refuge area, which contains 50% of the vaquita's habitat, the population is still in decline, which suggests a complete ban of gillnet use may be the only solution to saving the vaquita population.[28]

Other potential threats to the vaquita population include habitat alterations and pollutants. The habitat of the vaquita is small and the food supply in marine environments is affected by water quality and nutrient levels. The damming of the upper Colorado River has reduced the flow of fresh water into the gulf, potentially affecting the vaquita.[15] In addition, the use of chlorinated pesticides may also have a detrimental effect. Despite these possible problems, most of the recovered bodies of vaquitas show no signs of emaciation or environmental stressors,[15] implying that the decline is due almost solely to bycatch. However, these additional hazards may pose a long-term threat.

Secondary impact of declining numbers

Though the major cause of vaquita porpoise mortality is bycatch in gillnets, as numbers continue to dwindle, new problems will arise that will tend to make recovery more difficult. One such problem is reduced breeding rates. With fewer individuals in the habitat, less contact will occur between the sexes and consequently less reproduction. This may be followed by increased inbreeding and reduced genetic variability in the gene pool, following the bottleneck effect.

When inbreeding depression occurs, the population experiences reduced fitness because deleterious recessive genes can manifest in the population. In small populations where genetic variability is low, individuals are more genetically similar. When the genomes of mating pairs are more similar, recessive traits appear more often in offspring. The more related two individuals are in the breeding pair, the more deleterious homozygous genes the offspring will likely have which can greatly lower fitness in the offspring.[29] These secondary impacts of dwindling vaquita numbers are not necessarily a threat yet, but they will become problematic if the population continues to decline.[30]

Ecological consequences

Removal of the vaquita will have a significant ecological impact on the northern Gulf of California. The Gulf of California is considered a large marine ecosystem, due to its high species diversity and large habitat size.[31] With such biodiversity in the region, it is important to consider the potentially harmful effects of drops in the vaquita population on seemingly unrelated species due to apparent competition.

Sharks have been determined to be the only predators of vaquitas. Due to its limited number of predator species, the vaquita population is sensitive to small changes in predation from sharks.[31] Although the vaquita accounts for only a small percentage of the diets of sharks in the region, extinction of the vaquita could potentially cause negative effects on shark population sizes. Extinction of the vaquita may also impact the vaquita prey populations in the northern Gulf ecosystem. The disappearance of the vaquita could lead to potential over-population of their prey species such as benthic fishes, squid, and crustaceans.[15]

Conservation efforts for the vaquita are mainly focused on fishing restrictions to prevent their bycatch. These fishing restrictions could prove beneficial for the fish in the upper Gulf, as well as the vaquita. As a result of increased restrictions on gillnet use, the populations of the targeted fish and shrimp species will receive protection from overfishing.[32] Historically, numerous commercially fished species have experienced devastating impacts due to overfishing, and the vaquita conservation program may lessen the severity of such devastation in the future.[32] Another solution to prevent vaquita bycatch might be to redesign fishing nets, which could be used to effectively catch fish, but leave the vaquita untouched.

Recovery efforts

Because vaquitas are indigenous to the Gulf of California, Mexico is leading conservation efforts with the creation of the International Committee for the Recovery of the Vaquita (CIRVA), which has tried to prevent the accidental deaths of vaquita by outlawing the use of fishing nets within the vaquita's habitat.[7] CIRVA has worked with the CITES, the ESA, and the Marine Mammal Protection Act to make a plan to nurse the vaquita population back to a point at which they can sustain themselves.[9] CIRVA concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. 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 recommends 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. In November 2014, Greenpeace UK launched a campaign urging its members to write to Mexican President Enrique Peña Nieto to do just this, as well as commence dialogue with the Chinese and US over the commercial transport and consumption of products from species that threaten the vaquita's future, such as the similarly sized totoaba fish which is used in Chinese medicine.[33] In December 2015, Sea Shepherd Conservation Society launched Operation Milagro II, a direct action campaign to protect the endangered vaquita. Sea Shepherd partnered with the Mexican government in a joint effort to remove illegal nets, release trapped wildlife, obtain visual evidence of poaching in the area and conduct outreach with local communities and marine biologists.[34]

On 28 October 2008, Canada, Mexico, and the United States launched the North American Conservation Action Plan (NACAP) for the vaquita, under the jurisdiction of the Commission for Environmental Cooperation, a NAFTA environmental organization.[35] The NACAP is a strategy to support Mexico's efforts to recover the vaquita. Also in 2008, Mexico launched the program PACE-VAQUITA, another effort to help preserve the species. PACE-VAQUITA compensates fishermen who choose one of three alternatives: rent-out, switch-out, and buy-out.

In the rent-out option, fishermen acquire temporary contractual obligations to carry out conservation efforts. They are paid if they agree to terminate their fishing inside the vaquita refuge area. There is a penalty if fishermen breach the contract which includes getting their vessels taken by the government. The switch-out option provides fishermen with compensation for switching to vaquita-safe harvesting technology. Finally, the buy-back program compensates fisherman for permanently turning in their fishing permits, as well as their respective gear.[36] In 2008, because of how few fisherman were enrolling in the switch-out option, PACE Vaquita added a yearly, short-term option for fishermen, letting them simply rent the vaquita-safe fishing equipment yearly for compensation. Then, in 2010, this option was broken down even further, giving fishermen the option of buying the vaquita-safe net, or paying the yearly rent, but for less compensation.[16] Despite these efforts, the probability that these attempts at conservation will work is slim. Only about a third of fishermen in the area have accepted these terms so far. Some fishermen continue to fish in the protected areas despite the economic alternatives. Even measuring the population size of the vaquita will be difficult as the rarity of the vaquita bycatch will make it difficult to demonstrate the difference these programs are making.[36]

Another scheme for preserving the species that has been proposed is a captive breeding program.[37]

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.

  1. 1 2 3 Rojas-Bracho, L.; Reeves, R. R.; Jaramillo-Legorreta, A.; Taylor, B. L. (2008). "Phocoena sinus". IUCN Red List of Threatened Species. IUCN. 2008: e.T17028A6735464. doi:10.2305/IUCN.UK.2008.RLTS.T17028A6735464.en. Retrieved 2016-10-13.
  2. ↑ Turvey, S. T.; Brandon, J. R.; Richlen, M.; Pusser, L. T.; Zhang, X.; Wei, Z.; Wang, K.; Stewart, B. S.; Reeves, R. R.; Zhao, X.; Barrett, L. A.; Akamatsu, T.; Barlow, J.; Taylor, B. L.; Pitman, R. L.; Wang, D. (22 October 2007). "First human-caused extinction of a cetacean species?". Biology Letters. 3 (5): 537–540. doi:10.1098/rsbl.2007.0292. PMC 2391192Freely accessible. PMID 17686754.
  3. ↑ Jaramillo-Legorreta, A.; Rojas-Bracho, L.; Brownell, R. L.; Read, A. J.; Reeves, R. R.; Ralls, K.; Taylor, B. L. (15 November 2007). "Saving the vaquita: immediate action, not more data". Conservation Biology: 1653–1655. doi:10.1111/j.1523-1739.2007.00825.x.
  4. 1 2 3 4 Johnson, Chris (3 August 2014). "Report: Vaquita population declines to less than 100". Vaquita: Last Chance for the Desert Porpoise. earthOcean. Retrieved 11 August 2014.
  5. 1 2 3 4 Report of the Fifth Meeting of the Comité Internacional para la Recuperación de la Vaquita (PDF). Ensenada, Baja California: Comité Internacional para la Recuperación de la Vaquita (CIRVA). 3 August 2014. Retrieved 12 August 2014.
  6. 1 2 3 Sanders, Natalie (14 May 2016). "Stronger protection needed to prevent imminent extinction of Mexican porpoise vaquita, new survey finds". www.iucn-csg.org. IUCN Species Survival Commission. Retrieved 16 May 2016.
  7. 1 2 3 4 5 6 Barlow, J. (2014). "Vaquita (Phocoena sinus)". EDGE of Existence programme. Zoological Society of London. Retrieved 20 January 2014.
  8. ↑ Hohn, A. A.; Read, A. J.; Fernandez, S.; Vidal, O.; Findley, L. T. (June 1996). "Life history of the vaquita, Phocoena sinus (Phocoenidae, Cetacea)". Journal of Zoology. 239 (2): 235–251. doi:10.1111/j.1469-7998.1996.tb05450.x.
  9. 1 2 "Gulf of California Harbor Porpoise / Vaquita / Cochito (Phocoena sinus)". Species Information. NOAA Fisheries Office of Protected Resources. 8 July 2013. Retrieved 20 January 2014.
  10. ↑ "About the Vaquita". Save The Vaquita Project. January 2014. Retrieved 20 January 2014.
  11. ↑ "Vaquitas, Phocoena sinus". MarineBio.org. MarineBio Conservation Society. 14 January 2013. Retrieved 20 January 2014.
  12. ↑ "Basic Facts About Vaquitas". Wild Places and Wildlife. Defenders of Wildlife. 2013. Retrieved 20 January 2014.
  13. ↑ Rojas-Bracho, L. "Vaquita (P. sinus)". Species fact Sheets. Society for Marine Mammalogy. Retrieved 20 January 2014.
  14. ↑ Rice, Danielle (2 May 2011). "About the Vaquita: An Endangered Animal". Vaquita: An Endangered Species. Retrieved 20 January 2014.
  15. 1 2 3 4 Rojas-Bracho, L.; Reeves, R. R.; Jaramillo-Legorreta, A. (13 November 2006). "Conservation of the vaquita Phocoena sinus". Mammal Review. 36 (3): 179–216. doi:10.1111/j.1365-2907.2006.00088.x.
  16. 1 2 Avila-Forcada, S.; Martínez-Cruz, A. N. L.; Muñoz-Piña, C. (May 2012). "Conservation of vaquita marina in the Northern Gulf of California". Marine Policy. 36 (3): 613–622. doi:10.1016/j.marpol.2011.10.012.
  17. ↑ Jefferson, Thomas A.; Webber, Marc A.; Pitman, Robert L. (29 August 2011). Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press. pp. 288–289. ISBN 978-0-08-055784-7. OCLC 326418543.
  18. 1 2 "Vaquita (Phocoena sinus)". Encyclopedia of Endangered Species. Volume 1. Gale. 1 February 2009. Retrieved 2 November 2011.
  19. ↑ Pompa, S.; Ehrlich, P. R.; Ceballos, G. (16 August 2011). "Global distribution and conservation of marine mammals". Proceedings of the National Academy of Sciences. 108 (33): 13600–13605. doi:10.1073/pnas.1101525108.
  20. ↑ Carwardine, Mark (1995). Whales, Dolphins and Porpoises. Dorling Kindersley. ISBN 978-1-4053-5794-4. OCLC 31010070.
  21. 1 2 Aquarium Passport Book, Aquarium of the Pacific, 2005.
  22. ↑ "¡Viva Vaquita!". ¡Viva.
  23. ↑ Taylor, B. L.; Rojas-Bracho, L. (October 1999). "Examining the risk of inbreeding depression in a naturally rare cetacean, the vaquita (Phocoena sinus)". Marine Mammal Science. 15 (4): 1004–1028. doi:10.1111/j.1748-7692.1999.tb00875.x.
  24. ↑ "U.S. supports Mexico's efforts to save the vaquita". El Universal. 16 April 2015.
  25. ↑ Malkin, E. (16 April 2015). "Mexico's President Rolls Out Plan to Save Endangered Porpoise". The New York Times.
  26. ↑ Smith, Zak (16 March 2015). "The Call to Ban Mexican Seafood Products Gets Louder After Mexico Announces its Plan for Vaquita Extinction". nrdc.org.
  27. ↑ d'Agrosa, C.; Lennert-Cody, C. E.; Vidal, O. (August 2000). "Vaquita bycatch in Mexico's artisanal gillnet fisheries: driving a small population to extinction". Conservation Biology. 14 (4): 1110–1119. doi:10.1046/j.1523-1739.2000.98191.x.
  28. ↑ Gerrodette, T.; Taylor, B. L.; Swift, R.; Rankin, S.; Jaramillo-Legorreta, A. M.; Rojas-Bracho, L. (2011). "A combined visual and acoustic estimate of 2008 abundance, and change in abundance since 1997, for the vaquita, Phocoena sinus". Marine Mammal Science. 27 (2): E79–E100. doi:10.1111/j.1748-7692.2010.00438.x.
  29. ↑ CIRVA committee, Report of the Fourth Meeting of the International Committee for the Recovery of the Vaquita (CIRVA). IUCN. 2012
  30. ↑ Rojas-Bracho, L.; Taylor, B. L. (October 1999). "Risk factors affecting the vaquita (Phocoena sinus)". Marine Mammal Science. 15 (4): 974–989. doi:10.1111/j.1748-7692.1999.tb00873.x.
  31. 1 2 Díaz-Uribe, J. G.; Arreguín-Sánchez, F.; Lercari-Bernier, D.; Cruz-Escalona, V. C. H.; Zetina-Rejón, M. J.; Del-Monte-Luna, P.; Martínez-Aguilar, S. (10 April 2012). "An integrated ecosystem trophic model for the North and Central Gulf of California: An alternative view for endemic species conservation". Ecological Modelling. 230: 73–91. doi:10.1016/j.ecolmodel.2012.01.009.
  32. 1 2 Elton, Catherine (November–December 2011). "Safety Net". Audubon. 113 (6): 74–80. Retrieved 20 January 2014.
  33. ↑ "Last Chance to Save the Vaquita?". Greenpeace.org.uk. 2014. Retrieved 26 November 2014.
  34. ↑ http://www.seashepherd.org/milagro2/about-campaign/about-the-campaign.html
  35. ↑ "Recovering the Vaquita and Promoting Sustainable Local Livelihoods: Project Summary". Commission for Environmental Cooperation. 2011. Retrieved 5 November 2011.
  36. 1 2 Gerrodette, T.; Rojas-Bracho, L. (7 February 2011). "Estimating the success of protected areas for the vaquita, Phocoena sinus". Marine Mammal Science. 27 (2): E101–E125. doi:10.1111/j.1748-7692.2010.00449.x.
  37. ↑ Goldfarb, B. (2016-08-12). "Can captive breeding save Mexico's vaquita?". Science. 353 (6300): 633–634. doi:10.1126/science.353.6300.633.

Further reading

This article is issued from Wikipedia - version of the 11/23/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.