Langbahn Team – Weltmeisterschaft

Vaquita

Vaquita
Temporal range: Holocene [1]
Size compared to an average human
CITES Appendix I (CITES)[3]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Phocoenidae
Genus: Phocoena
Species:
P. sinus
Binomial name
Phocoena sinus
Norris & McFarland, 1958
Map
IUCN range of the Vaquita
  Extant (resident)

The vaquita (/vəˈkiːtə/ və-KEE-tə; Phocoena sinus) is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Reaching a maximum body length of 150 cm (4.9 ft) (females) or 140 cm (4.6 ft) (males), it is the smallest of all living cetaceans.

The species is currently on the brink of extinction, and is listed as Critically Endangered by the IUCN Red List;[2] the steep decline in abundance is primarily due to bycatch in gillnets from the illegal totoaba fishery.[4][2]

Taxonomy

The vaquita was defined as a species by two zoologists, Kenneth S. Norris and William N. McFarland, in 1958 after studying the morphology of skull specimens found on the beach.[5] It was not until nearly thirty years later, in 1985, that fresh specimens allowed scientists to describe their external appearance fully.[6]

The genus Phocoena comprises four species of porpoise, most of which inhabit coastal waters (the spectacled porpoise is more oceanic). The vaquita is most closely related to Burmeister's porpoise (Phocoena spinipinnis) and less so to the spectacled porpoise (Phocoena dioptrica), two species limited to the Southern Hemisphere. Their ancestors are thought to have moved north across the equator more than 2.5 million years ago during a period of cooling in the Pleistocene.[7][8][failed verification] Genome sequencing from an individual captured in 2017 indicates that the ancestral vaquitas had already gone through a major population bottleneck in the past, which may explain why the few remaining individuals are still healthy despite the very low population size.[9]

"Vaquita" is Spanish for "little cow".[10]

Description

Characteristic dark eye rings

The smallest living species of cetacean, the vaquita can be easily distinguished from any other species in its range. It has a small body with an unusually tall triangular dorsal fin, a rounded head, and no distinguished beak. The coloration is mostly grey with a darker back and a white ventral field. Prominent black patches surround its lips and eyes.[11] Sexual dimorphism is apparent in body size, with mature females being longer than males and having larger heads and wider flippers.[8][failed verification][12] Females reach a maximum size of about 150 cm (4.9 ft), while males reach about 140 cm (4.6 ft).[13] Dorsal fin height is greater in males than in females.[8][failed verification][12] They are also known to weigh around 27 kg (60 lb) to 68 kg (150 lb). This makes them one of the smallest species in the porpoise family.[14]

Distribution and habitat

Vaquita habitat is restricted to a small portion of the upper Gulf of California (also called the Sea of Cortez), making this the smallest range of any cetacean species. They live in shallow, turbid waters of less than 150 m (490 ft) depth.[2]

Diet

Vaquitas are generalists, foraging on a variety of demersal fish species, crustaceans, and squids, though benthic fish such as grunts and croakers make up most of the diet.[2]

Social behavior

A pair of vaquitas

Vaquitas are generally seen alone or in pairs, often with a calf, but have been observed in small groups of up to 10 individuals.[2]

Little is known about the life history of this species. Life expectancy is estimated at about 20 years and age of sexual maturity is somewhere between 3 and 6 years of age.[15] While an initial analysis of stranded vaquitas estimated a two-year calving interval,[16] recent sightings data suggest that vaquitas can reproduce annually.[17] It is thought that vaquitas have a polygynous mating system in which males compete for females. This competition is evidenced by the presence of sexual dimorphism (females are larger than males), small group sizes, and large testes (accounting for nearly 3% of body mass).[16]

Population status

Because the vaquita was only fully described in the late 1980s, historical abundance is unknown.[18] Since 1983, all confirmed specimens, records, and sightings of P. sinus were evaluated. There were 45 records of P. sinus that were collected by skeletal remains, photographs, and sightings in 1983.[19] The first comprehensive vaquita survey throughout their range took place in 1997 and estimated a population of 567 individuals.[20] By 2007 abundance was estimated to have dropped to 150.[21] Population abundance as of 2018 was estimated at less than 19 individuals.[22] Given the continued rate of bycatch and low reproductive output from a small population, it is estimated that there are fewer than 10 vaquitas alive as of February 2022.[23][failed verification][24][25] In 2023, it is still estimated that there are as few as 10 in the wild.[26] A 2024 survey observed a minimum of 6 to 8 individuals (with a maximum of 9 to 11), the lowest ever count, but this number may just be a result of the small survey area instead of an actual population decline, as vaquitas freely move in and out of the survey region.[27][28]

Reproduction

Vaquitas reach sexual maturity from three to six years old. Vaquitas have synchronous reproduction, suggesting that calving span is greater than a year. Their pregnancies last from 10 to 11 months, and vaquita calves are nursed by their mothers for 6–8 months until becoming independent.[29] Vaquitas give birth about every other year to a single calf, usually between the months of February and April.[14][30] Because of their low reproduction rates, long gestation periods and larger species size, vaquitas are considered a K-selected species.[31][additional citation(s) needed] K-selected species are more vulnerable to extinction as they cannot repopulate at the rate of r-selected species.[32][failed verification] Vaquitas are on the brink of extinction because their numbers are few and they cannot replenish their population fast enough to exceed the number of vaquitas dying off.[citation needed]

Threats

Fisheries bycatch

A vaquita swims in the foreground with fishing boats in the distance

Anthropogenic effects of a rise in commercial fishing such as accidental bycatch, illegal fishing, and entanglement have been linked to the cause of their decline.[33][page needed] Shrimp fishing and gillnets create entanglement issues for the vaquita.[34] Aspects of illegal fishing include open access fisheries and absent fisheries management has correlated towards poaching of the main prey source of the vaquita.[35]

The drastic decline in vaquita abundance is the result of fisheries bycatch in commercial and illegal gillnets, including fisheries targeting the now-vulnerable Totoaba, shrimp, and other available fish species.[4][36] Despite government regulations, including a partial gillnet ban in 2015 and establishment of a permanent gillnet exclusion zone in 2017, illegal totoaba fishing remains prevalent in vaquita habitat, and as a result the population has continued to decline.[22] Fewer than 19 vaquitas remained in the wild in 2018. Large-mesh gillnets used in illegal fishing for totoaba caused an increase in the rate of loss of vaquitas after 2011.[37]

In 2021, the Mexican government eliminated a "no tolerance" zone in the Upper Gulf of California and opened it up to fishing.[38][dubious – discuss]

In 2022 the navy began to place concrete blocks with rebar hooks into what is considered the primary area for vaquita, which was designated as a zero tolerance area (ZTA) for fishing in 2020. These are known to destroy gillnets (which can cost tens of thousands of dollars) in shallower waters. Their deployment had an immediate effect on the number of fishing boats in the area. Citing reports of echolocation outside of the ZTA, the navy expanded the area in which these blocks were placed starting in November 2023 with plans to continue placing new blocks until the end of June 2024. There are some concerns that the hooks will create ghost nets, and the navy and Sea Shepherd have removed nets trapped on hooks after being caught.[39]

Other threats

Given their proximity to the coast, vaquitas are exposed to habitat alteration and pollution from runoff. Pesticides present in the water as a result of runoff from agriculture are a threat as they can be ingested by the vaquitas, causing harm and even death. [40] Exposure to toxic compounds has also had a deleterious effect on vaquitas.[41] Bycatch, which is the incidental catch of non-target species in fishing gear, is not only the largest threat to the survival of the vaquita, but to all marine mammals around the world.[42][43][failed verification] A series of simulations in a 2022 study indicate that the species has a chance to survive and recover if all bycatch is halted, despite the presence of other threats.[44] However, the biggest threat still towards vaquita are fisheries. Northern fishing fleets have had an indirect positive impact mainly on marine mammals, because fishing on predators like sharks reduces its predatory negative impact on those groups. Although the predation of sharks towards vaquita do result in a decline in population and is seen as an alternate threat, northern fishing fleets also negatively impact this small marine mammal because the negative influence of incidental catch is greater than the positive influence of predation reduction by shark fisheries.[45]

Populations that experience a sudden decline in numbers are often more vulnerable to other threats in the future due to a bottleneck of genetic diversity within the reduced population. The reduced gene pool lowers the rate of adaptation and increases the rate of inbreeding, potentially leading to inbreeding depression. This phenomenon is attributed to the anthropogenic Allee effect, specifically on the end where small population size leads to low species fitness because of a lack of genetic diversity and the potential for inbreeding. Because of their small population size, vaquitas are experiencing a negative Allee effect, attributing to even smaller population growth rates, driving them further into extinction. [46] However, a 2022 study on the genetic diversity of the vaquita suggests that the marine mammal’s historically small population ensures it is unlikely to greatly suffer from inbreeding depression.[44]

Attempts to start a population in captivity have proved to be more threatening to the population than helpful. A November 2017 effort ended up traumatizing and killing one female vaquita, as well as invoking unnecessary stress onto a juvenile.[47] Still, creating a captive population could be used as a last resort to save the species and to further educate on vaquitas.[48][failed verification]

Conservation

Conservation status

The vaquita is listed as critically endangered on the IUCN Red List, which is only one level above being completely extinct in the wild. It is considered the most endangered marine mammal in the world. The vaquita has been listed as critically endangered by the IUCN Red List of Threatened Species since 1996.[2] The vaquita is at risk of extinction due to its small population size.[33][page needed] It was approximated at one point that there were 150 individuals.[21]

In 2019, the UNESCO World Heritage Site where the last vaquita are located was classified as a World Heritage Site in Danger.[49]

The vaquita is also protected under the Endangered Species Act of 1973, the Mexican Official Standard NOM-059 (Norma Oficial Mexicana), and Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).[3]

For a small population such as the vaquita to recover after a severe decline in population size is very difficult. This conservation status is strongly influenced in part of the species reproductive biology. The large amount of unknown surrounding the key reproductive parameters of the vaquita makes understanding its potential for recovery even harder.[2]

Conservation efforts

The vaquita is found only in the upper Gulf of California, Mexico area.[50] Anthropogenic effects of a rise in commercial fishing such as accidental by-catch, illegal fishing, and entanglement have been linked to the cause of their decline.[33][page needed] Shrimp fishing and gillnets create entanglement issues for the vaquita.[34] Aspects of illegal fishing include open access fisheries and absent fisheries management have correlated towards poaching of the main prey source of the vaquita.[35] The swim bladders of the Totoaba macdonaldi are being sold on the black market by cartels for profit.[34]

The Mexican government, international committees, scientists, and conservation groups have recommended and implemented plans to help reduce the rate of bycatch, enforce gillnet bans, and promote population recovery.[citation needed]

Protection efforts throughout Mexico have taken place in order to preserve the population. In 2017, the Government of Mexico established it as a felony to remove an endangered species.[35] Alongside this, the Government of Mexico also made a public agreement to prohibit gillnet use.[35] Efforts are proactive in incentive applications to fisheries in a system of trade-offs that benefit fishermen and the vaquita.[51][failed verification]

Mexico launched a program in 2008 called PACE-VAQUITA in an effort to enforce the gillnet ban in the Biosphere Reserve, allow fishermen to swap their gillnets for vaquita-safe fishing gear, and provide economic support to fishermen for surrendering fishing permits and pursuing alternative livelihoods.[52] Despite the progress made with legal fishermen, hundreds of poachers continued to fish in the exclusion zone. Poaching continues as the swim bladders of totoaba can sell for anywhere from $20,000 to upwards of $80,000, and they are often referred to as the "cocaine of the sea."[53] A black market for totoaba swim bladders has developed fairly recently in China (including Hong Kong). In 2017, poachers received up to US$20,000 for a kilogram of totoaba swim bladders, with some making as much as $116,000 in one day.[54]

The swim bladders of the Totoaba macdonaldi are being sold on the black market by cartel for profit.[34] With continued illegal totoaba fishing, which is largely motivated by sales to the Chinese market where it is used in traditional medicine, and uncontrolled bycatch of vaquitas, the International Committee for the Recovery of the Vaquita (CIRVA) recommended that some vaquitas be removed from the high-density fishing area and be relocated to protected sea pens. This effort, called VaquitaCPR,[55] captured two vaquitas in 2017; one was later released and the other died shortly after capture after both suffered from shock.[56]

Local and international conservation groups, including Museo de Ballena and Sea Shepherd Conservation Society, are working with the Mexican Navy to detect fishing in the Refuge Area and remove illegal gillnets.[52] In March 2020, the U.S. National Marine Fisheries Service (NMFS) announced a ban on imported Mexican shrimp and other seafood caught in vaquita habitat in the northern Gulf of California.[57]

In response to the dire circumstances facing the vaquita as by-catch of the illegal totoaba trade, in 2017 Earth League International (ELI) commenced an investigation and intelligence gathering operation called Operation Fake Gold, during which the entire illicit totoaba maw (swim bladder) international supply chain, from Mexico to China, has been mapped and researched. Thanks to the confidential data that ELI shared with the Mexican authorities, in November 2020, a series of important arrests were made in Mexico.[58]

To date, efforts have been unsuccessful in solving the complex socioeconomic and environmental issues that affect vaquita conservation and the greater Gulf of California ecosystem. Necessary action includes habitat protection, resource management, education, fisheries enforcement, alternative livelihoods for fishermen, and raising awareness of the vaquita and associated issues.[2]

Jaramillo-Legorreta, et al. stated in 2007 that captive breeding programs were not a viable option for saving the species from extinction.[59]

The Secretariat of Environment and Natural Resources (SEMARNAT) announced on February 27, 2021, that it may reduce the protected area for the vaquita in the Sea of Cortés as there are only ten of the porpoises left and it may never recuperate its historical range.[60]

Beginning in July 2022, the Mexican government placed 193 concrete blocks in the Gulf of California no-tolerance zone, intended to allow the detection of nets by acoustic sonar and prevent further entrapment of vaquitas.[61]

Creating protected areas is always an option for conservationists, but because the vaquita's range is so small, there would be no use in trying to establish habitat corridors. One option for conservationists could be trying to create buffer zones near the coast in which pesticides harmful to vaquitas are restricted or even unavailable in order to enhance the protection value of the vaquita's range.[citation needed]

In May 2023, a wildlife survey expedition discovered that the population had stabilized since it had last been recorded in 2021.[62]

In October 2024, Colossal Biosciences announced their non-profit foundation dedicated to conservation of extant species, with one of their first projects being the vaquita. Colossal plans to biobank genetic material to revive the species if it were to become extinct, and to use acoustic sensors and drones to monitor vaquitas in collaboration with CONANP.[63][64]

Consumers

Roughly 80% of shrimp caught in the northern end of the Gulf of California, which has a high aquatic mammal bycatch rate, is consumed in the United States. As such, U.S. consumers of this shrimp are likely contributing to the vaquita extinction crisis. The Marine Mammal Protection Act of 1972, which forbids foreign fishers from exporting seafood with high levels of marine mammal bycatch, may allow for better efforts to preserve endangered vaquitas.[65]

See also

  • Baiji - Another critically endangered/functionally extinct cetacean in modern times
  • Illegal drug trade - The main factor of the vaquitas functional extinction
  • Holocene extinction - Ongoing mass-extinction event primarily consisting of manmade extinctions

References

  1. ^ fossilworks.
  2. ^ a b c d e f g h i Rojas-Bracho, Taylor & Jaramillo-Legorreta 2022.
  3. ^ a b CITES 2023.
  4. ^ a b Rojas-Bracho & Reeves 2013, p. 78.
  5. ^ Norris & McFarland 1958, p. 24–26.
  6. ^ Brownell et al. 1987, p. 23.
  7. ^ Rojas-Bracho, Reeves & Jaramillo-Legorreta 2006, Distribution.
  8. ^ a b c Brownell et al. 1987.
  9. ^ Casanueva 2020.
  10. ^ McNamee 2011.
  11. ^ Brownell et al. 1987, pp. 27–29.
  12. ^ a b Torre, Vidal & Brownell 2014, p. 1288.
  13. ^ Brownell et al. 1987, pp. 23–24.
  14. ^ a b NOAA 2023.
  15. ^ Hohn et al. 1996, pp. 244, 247.
  16. ^ a b Hohn et al. 1996, pp. 249.
  17. ^ Taylor et al. 2019.
  18. ^ Rojas-Bracho, Reeves & Jaramillo-Legorreta 2006, Abundance.
  19. ^ Brownell 1986, p. 299.
  20. ^ Jaramillo-Legorreta, Rojas-Bracho & Gerrodette 1999, p. 957.
  21. ^ a b Jaramillo-Legorreta et al. 2007, p. 1653.
  22. ^ a b Jaramillo-Legorreta et al. 2019, Discussion and conclusion.
  23. ^ Jaramillo-Legorreta et al. 2019.
  24. ^ Canon 2022.
  25. ^ CIRVA 2019, p. 5.
  26. ^ World Wildlife Fund.
  27. ^ devon11 (11 June 2024). "Vaquita Survey 2024 - Executive Summary". Sea Shepherd Conservation Society. Retrieved 11 June 2024.{{cite web}}: CS1 maint: numeric names: authors list (link)
  28. ^ Einhorn, Catrin (11 June 2024). "The Most Endangered Marine Mammal Still Exists. Here's the Latest Count". The New York Times. ISSN 0362-4331. Retrieved 11 June 2024.
  29. ^ Setiawati, Rahayu & Setiadi 2017.
  30. ^ Hohn et al. 1996, pp. 240, 248–249.
  31. ^ Rafferty 2023a.
  32. ^ Pimm 2023.
  33. ^ a b c Aragón-Noriega et al. 2010.
  34. ^ a b c d Dunch 2019, p. 583.
  35. ^ a b c d Sanjurjo-Rivera et al. 2021.
  36. ^ Rojas-Bracho, Reeves & Jaramillo-Legorreta 2006, Life history.
  37. ^ Morin et al. 2021, p. 1010.
  38. ^ Alberts 2021.
  39. ^ Daniel Shailer (24 May 2024). "Fishers decry 'underhanded' new initiative to protect Mexico's vaquita". Mongabay. Retrieved 29 May 2024.
  40. ^ Rafferty 2023b.
  41. ^ Lam et al. 2020, p. 3.
  42. ^ Marine Mammal Commission 2023.
  43. ^ CIRVA 2019.
  44. ^ a b Robinson et al. 2022.
  45. ^ Díaz-Uribe et al. 2012, pp. 80–81.
  46. ^ Courchamp et al. 2006.
  47. ^ Pennisi 2017.
  48. ^ Jaramillo-Legorreta et al. 2007.
  49. ^ Schatzberg, Simon (4 July 2019). "UNESCO declares vaquita marina habitat World Heritage in danger". Mexico News Daily. Retrieved 1 September 2023.
  50. ^ Morzaria-Luna et al. 2012, Introduction.
  51. ^ Morzaria-Luna et al. 2012.
  52. ^ a b Rojas-Bracho & Taylor 2021.
  53. ^ Delgado 2012, pp. 73–103.
  54. ^ Rojas-Bracho et al. 2019, pp. 12.
  55. ^ VaquitaCPR 2019.
  56. ^ Rojas-Bracho et al. 2019, pp. 17.
  57. ^ Natural Resource Defense Council 2020.
  58. ^ Linares 2023.
  59. ^ Jaramillo-Legorreta et al. 2007, p. 1654.
  60. ^ The Associated Press 2021.
  61. ^ Yucatan Times 2022.
  62. ^ Bernal, Rafael (10 June 2023). "Expedition finds resilient population of world's endangered vaquita porpoise". The Hill.
  63. ^ Innovates, Dallas; Murray, Lance (1 October 2024). "Colossal Launches The Colossal Foundation with $50M for 'BioVault' Biobanking, Genetic Rescues, and More". Dallas Innovates. Retrieved 5 October 2024.
  64. ^ "Rescuing the Panda of the Sea". Colossal Foundation. Retrieved 5 October 2024.
  65. ^ Dunch 2019, p. 584.

Sources

Further reading

To learn more about the vaquita and conservation efforts, visit:

Quelle: https://en.wikipedia.org/wiki/Vaquita