Yangtze finless porpoise

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Yangtze finless porpoise
Yangtze finless porpoise, 10 November 2006.jpg
At the Chinese Academy of Sciences
CITES Appendix I (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Phocoenidae
Genus: Neophocaena
Species:
N. asiaeorientalis
Binomial name
Neophocaena asiaeorientalis
(Pilleri & Gihr, 1972)
Chinaporpoise.png
Yangtze finless porpoise distribution

The Yangtze finless porpoise (Neophocaena asiaeorientalis) is a species of toothed whale in the family Phocoenidae, the porpoise family. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible extinction of the baiji (Lipotes vexillifer), a freshwater dolphin also native to the Yangtze. [3] The Yangtze finless porpoise is considered endangered and it is estimated that only about 1,000 remain. [4] This small toothed whale faces many of the same threats as the baiji: High human activity on the Yangtze, such as illegal fishing, pollution, boat traffic, and dam construction. Due to the rapidly declining population of the species, the Chinese government and conservation charities are working to help save it from extinction. [5]

Contents

Taxonomy

The Yangtze finless porpoise is considered a freshwater cetacean (whales, dolphins, and porpoises that live in a variety of aquatic habitats). The finless porpoise originally inhabited salt water niches along the coast of the Indo-Pacific Ocean. However, a population dispersed into the fresh water environment of the Yangtze River. Recent studies have found that the East Asian finless porpoise (N. sunameri) and the Yangtze finless porpoise (N. asiaeorientalis) have had separate reproduction and gene flow for thousands of years. The East Asian finless porpoise and the Yangtze finless porpoise were formerly considered one species going by the scientific name of N. phocaenoides, but genetic studies support the Yangtze finless porpoise being a distinct species, or at least an incipient one, due to the lack of gene flow. [3] [5]

Names

In Mandarin Chinese, it is known as jiangtun (Chinese : 江豚 , p  jiāngtún, lit. "river piglet")

Description

A finless porpoise can grow up to 2.27 m (7 ft 5+1⁄2 in) in length and weigh up to 71.8 kg (158+1⁄4 lb), however, most are smaller than this. The average adult is usually 1.5–1.8 m (5–6 ft) in length and weighs around 45 kg (100 lb). [6] Adult females tend to be smaller than adult males. Flippers are curved with pointed ends and are relative large, about 20% of their total body length. The finless porpoise tends to be stocky in the middle body and slimmer towards the tail. In general they are more slender in shape than most other Phocoenidae . These cetaceans also have unique foreheads, with a very steep forehead and no beak. [6] In addition, they have an unfused neck vertebrae that allows free head movement. They have 15–22 pairs of teeth on the upper and lower jaw. [7] Body color and dorsal ridge sizes vary depending on the geographical location of the finless porpoise. [6]

Dorsal ridge

As denoted by the name, these finless porpoises have flat backs and are completely finless. Instead of a dorsal fin, these porpoises have a dorsal ridge or "groove" that is covered in varying rows of tubercles. These tubercles are round in shape and raised. Recent studies have found that tubercles do have biological and mechanical functions that benefit the porpoise; for example, the tubercles are a sensory organ and can also help with movement through the water. [8] The amount of rows of tubercles and dorsal ridge sizes vary depending on the species and location of the porpoise. The East Asian finless porpoise and the Yangtze finless porpoise usually have a higher and narrower ridge with only 1 - 10 rows of tubercles, whereas the Indo-Pacific finless porpoise (Neophocaena phocaenoides) tends to have a lower and wider ridge with 10–25 rows of tubercles. [6]

Body color

Body color also varies depending on habitat location and age. Newborn Yangtze finless porpoises and East Asian finless porpoises tend to be a dark gray or black color that lightens within a few months to a lighter gray. However, the Indo-Pacific species has a reverse trend, in which newborns are light in color and get darker with age. After death Yangtze finless porpoises usually become black in color. It is also very common for there to be lighter patches of color around the mouth and genitals; however this coloration is more noticeable at a young age. [6]

Habitat

The Yangtze finless porpoise is found in the main body of the Yangtze River and in connecting lakes. They are exclusive to fresh water, making them different from other finless porpoises. They tend to be found in shallow bay areas, swamps, and estuaries year round as they are not a migratory species. [5] However, distribution changes do occur seasonally. In the winter the highest distribution was found in the middle and lower regions of the Yangtze River. Their preferred climate is tropical or warm temperatures. [6]

Diet

The diet of the Yangtze finless porpoise may vary according to the season and the dominant prey of the season. This variation in their diet suggest that the Yangtze finless porpoise may be opportunistic feeders. Among the fishes in their diet, the most common are Coilia brachygnathus,Pseudobrama simoni,Pelteobagrus nitidus, and Hemiculter bleekeri. [9]

Behavior

The Yangtze finless porpoise tends to be shy; it does not come to the surface of the water often when there is human activity nearby. They are usually most active when eating and usually spend most of their time near river banks or at the merging of two waterways. Yangtze finless porpoises travel in small groups of about three to six; however groups of 20 have been reported. [6] A radio-tracking study confirmed that the average diving behavior consisted of one long dive followed by two shorter dives. These longer dives were more common during the day time. [6] In the Yangtze River, finless porpoises are known to leap from the water and perform "tail stands". [6] At night the finless porpoises tended to go into sleep cycles and be less active. Another unique behavior reported, but that is not heavily confirmed, is that mothers have been seen carrying calves on their backs. [7] An additional uncommon aspect of the finless porpoise is their method of communication. Rather than communicating through whistles, as most dolphin species do, these porpoises use echolocation and ultrasonic pulses [10]

Status

After the functional extinction of the Yangtze river dolphin and the rapid decreasing of population, the Chinese government has given this species the utmost conservation status of National First Grade Key Protected Wild Animal to ensure its survival. However, the population decrease is accelerating due to lack of food, pollution, and ship movement, and the species has a high chance (86.06%) of becoming extinct within the next 100 years. [11] Another reason that they have been dropping in numbers is because of underwater noise pollution. If spectra levels in the water surpass the underwater acoustic thresholds for the porpoise, their chance of survival is greatly threatened. [12] Global conservation agencies and charities, such as the World Wildlife Fund and IUCN, have been collaborating with the Chinese government to ensure the survival of the species.

Threats

Fishing

Bycatch by unwary fishermen may be a factor for the ongoing decline of the Yangtze finless porpoise. Illegal fishing and hazardous gear, like gillnets, is widely used in the Yangtze River. The preferred habitat of the Yangtze Finless Porpoise overlaps extensively with the usage of gillnets, which makes the species particularly vulnerable to entanglement and subsequent drowning. However, a recent large-scale interview survey conducted in fishing communities along the banks of the Yangtze, by the IUCN, suggests that mortality due to bycatch may have decreased over the past two decades as the porpoise population has declined, and have concluded that gillnetting is unlikely to be the primary cause of their decline.

Development

Wild individuals in Poyang Lake Yangtze finless porpoise, 9 January 2012a.jpg
Wild individuals in Poyang Lake

Increased traffic, pollution, and habitat degradation of the river have contributed to population declines. The increased vessel traffic may cause death from propeller strikes, and the boat noise may mask the porpoise's ability to communicate with other porpoises, as well as hindering their biosonar which compromises foraging and locomotion. Porpoise mortality associated with vessel collisions has increased substantially in recent years, in contrast to mortality from by-catch. [13]

Widespread sand mining of the river and lake beds and banks has destroyed important habitats for porpoises and food items, as well as other environmental issues. This problem is especially serious in the Dongting and Poyang Lakes. [14] There are currently 400 million people living along the river basin as well as thousands of factories, which together discharge tremendous quantities of domestic sewage and agricultural and industrial waste. It has not been proven that this impacts the Yangtze finless porpoise's health, fertility, or population. In April 2004, five porpoises died in Dongting Lake within a single week due to short-term exposure to pesticides, possibly in combination with long-term exposure to mercury and chromium. [15]

Dams have major effects on river and lake ecology, and inhibit access between the river and adjoining lakes or tributaries in the Yangtze, as well as affecting migrating prey items. The Three Gorges Dam in particular has altered and will continue to alter, downstream conditions in the Yangtze River and its connected/adjoining lakes. [13] Construction of the Poyang Lake Dam is likely to damage the remaining population severely. [16]

Conservation

As of 2014, 505 porpoises remain in the main section of the Yangtze, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of the porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. [17] A 2012 survey by the World Wildlife Fund indicated the rate of decline had accelerated to 13.7% per year. [18] By 2017, the number in the Yangtze had increased to 1,012. [19] Due to ongoing protection efforts, the porpoises have reappeared in places like Nantong, [20] where sightings had been rare in recent years.

A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately environmental degradation. [21] Some of these can be seen in damming of the river as well as illegal fishing activity. [13] To protect the species, China's Ministry of Agriculture classified the species as being National First Grade Key Protected Wild Animal, the strictest classification by law, meaning it is illegal to bring harm to a porpoise.

The Tian-e-Zhou Oxbow Nature Reserve has worked for years to protect the porpoises. The reserve, which is sponsored by the Chinese government, World Wildlife Fund, the Coca-Cola Company, and others, increased its porpoise population from five to forty in twenty-five years. By 2017, there were 80 individuals, nearing the total capacity of 100. [22] [23] The Chinese Academy of Science's Wuhan Institute of Hydrobiology has been working with the World Wildlife Fund to ensure the future for this subspecies, and have placed five porpoises in another well-protected area, the He-wang-miao oxbow. [24]

Five protected natural reserves have been established in areas of the highest population density and mortality rates with measures being taken to ban patrolling and harmful fishing gear in those areas. There have also been efforts to study porpoise biology to help specialize conservation through captive breeding. The Baiji Dolphinarium, was established in 1992 at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan which allows the study of behavioral and biological factors affecting the finless porpoise, specifically breeding biology like seasonal changes in reproductive hormones and breeding behavior. [25]

The first Yangtze finless porpoise was born in captivity on July 5, 2005, in Baji Dolphinarium in Wuhan. [26]

Related Research Articles

<span class="mw-page-title-main">Yangtze</span> Longest river in Asia

The Yangtze, Yangzi or Changjiang is the longest river in Eurasia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains of the Tibetan Plateau and flows 6,300 km (3,915 mi) in a generally easterly direction to the East China Sea. It is the fifth-largest primary river by discharge volume in the world. Its drainage basin comprises one-fifth of the land area of China, and is home to nearly one-third of the country's population.

<span class="mw-page-title-main">Porpoise</span> Small cetacean of the family Phocoenidae

Porpoises are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates.

<span class="mw-page-title-main">River dolphin</span> Superfamily of dolphins

River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant river dolphins are placed in two superfamilies, Platanistoidea and Inioidea. They comprise the families Platanistidae, the recently extinct Lipotidae, Iniidae and Pontoporiidae. There are five extant species of river dolphins. River dolphins, alongside other cetaceans, belong to the clade Artiodactyla, with even-toed ungulates, and their closest living relatives the hippopotamuses, from which they diverged about 40 million years ago. Specific types of dolphins can be pink.

<span class="mw-page-title-main">Indo-Pacific humpback dolphin</span> Species of mammal

The Indo-Pacific humpback dolphin is a species of humpback dolphin inhabiting coastal waters of the eastern Indian and western Pacific Oceans. This species is often referred to as the Chinese white dolphin in mainland China, Macau, Hong Kong, Singapore and Taiwan as a common name. Some biologists regard the Indo-Pacific dolphin as a subspecies of the Indian Ocean humpback dolphin which ranges from East Africa to India. However, DNA testing studies have shown that the two are distinct species. A new species, the Australian humpback dolphin, was split off from S. chinensis and recognized as a distinct species in 2014. Nevertheless, there are still several unresolved issues in differentiation of the Indian Ocean-type and Indo-Pacific-type humpback dolphins.

<span class="mw-page-title-main">Indo-Pacific finless porpoise</span> Species of porpoise

The Indo-Pacific finless porpoise is one of eight porpoise species. The species ranges throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait. Overlapping with this species in the Taiwan Strait and replacing it northwards is the East Asian finless porpoise.

<span class="mw-page-title-main">Finless porpoise</span> Genus of porpoises

Neophocaena is a genus of porpoise native to the Indian and Pacific oceans, as well as the freshwater habitats of the Yangtze River basin in China. They are commonly known as finless porpoises. Genetic studies indicate that Neophocaena is the most basal living member of the porpoise family.

<span class="mw-page-title-main">Indian Ocean humpback dolphin</span> Species of mammal

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<span class="mw-page-title-main">Cetacean bycatch</span> Accidental capture of porpoises, whales and dolphins

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The Tian-e-Zhou Oxbow Nature Reserve is an area of wetland in the Yangtze basin near Shishou, Hubei province, People's Republic of China. Inside the reserve is the Tian'e-Zhou lake which was an intended sanctuary for the baiji and is currently holding 28 finless porpoises.

<span class="mw-page-title-main">Hong Kong Dolphin Conservation Society</span>

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The Yangtze Freshwater Dolphin Expedition 2006 was a six-week search expedition undertaken in November and December 2006 in central China in an attempt to locate continued proof of the existence of the endangered baiji Yangtze dolphin. It was carried out under the direction of the Wuhan Institute of Hydrobiology and the Swiss-based baiji.org Foundation and was notable for drawing to an end without any positive results. Thus it was announced that the species was functionally extinct.

<span class="mw-page-title-main">Functional extinction</span> End of viability for a population

Functional extinction is the extinction of a species or other taxon such that:

  1. It disappears from the fossil record, or historic reports of its existence cease;
  2. The reduced population no longer plays a significant role in ecosystem function;
  3. The population is no longer viable. There are no individuals able to reproduce, or the small population of breeding individuals will not be able to sustain itself due to inbreeding depression and genetic drift, which leads to a loss of fitness.
<span class="mw-page-title-main">Baiji</span> Species of river dolphin

The baiji is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolphin species driven to extinction due to the impact of humans. This dolphin is listed as “critically endangered: possibly extinct” by the IUCN, has not been seen in 40 years, and several surveys of the Yangtze have failed to find it. In China, the species is also called the Chinese river dolphin, Han river dolphin, Yangtze dolphin and whitefin dolphin. Nicknamed the "Goddess of the Yangtze", it was regarded as the goddess of protection by local fishermen and boatmen. It is not to be confused with the Chinese white dolphin or the finless porpoise. This is the only species in the genus Lipotes.

<span class="mw-page-title-main">East Asian finless porpoise</span> Species of porpoise

The East Asian finless porpoise is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise was formerly considered a subspecies, but is now thought to be a distinct species.

Brauninidae is a monotypic family of trematodes in the order Diplostomida. It consists of one genus, Braunina Heider, 1900, which consists of one species, Braunina cordiformis Wolf, 1903.

<span class="mw-page-title-main">Cetacean microbiome</span>

The cetacean microbiome is the group of communities of microorganisms that reside within whales.

References

  1. ↑ Wang, D.; Turvey, S.T.; Zhao, X. & Mei, Z. (2013). "Neophocaena asiaeorientalis ssp. asiaeorientalis". IUCN Red List of Threatened Species . 2013: e.T43205774A45893487. doi: 10.2305/IUCN.UK.2013-1.RLTS.T43205774A45893487.en .
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  3. 1 2 Zhou, Xuming; Guang, Xuanmin; Sun, Di; Xu, Shixia; Li, Mingzhou; Seim, Inge; Jie, Wencai; Yang, Linfeng; Zhu, Qianhua; Xu, Jiabao; Gao, Qiang (2018-04-10). "Population genomics of finless porpoises reveal an incipient cetacean species adapted to freshwater". Nature Communications. 9 (1): 1276. Bibcode:2018NatCo...9.1276Z. doi:10.1038/s41467-018-03722-x. ISSN   2041-1723. PMC   5893588 . PMID   29636446.
  4. ↑ "Yangtze finless porpoise". WWF. Retrieved 2021-11-12.
  5. 1 2 3 "The IUCN Red List of Threatened Species". IUCN Red List of Threatened Species. Retrieved 2021-11-12.
  6. 1 2 3 4 5 6 7 8 9 Jefferson, T. A.; Hung, S. K. (2004). "Neophocaena phocaenoides". Mammalian Species. 746: 1–12. doi: 10.1644/746 . S2CID   198125391.
  7. 1 2 "OBIS-SEAMAP Species Profile - Neophocaena phocaenoides". seamap.env.duke.edu. Retrieved 2021-11-12.
  8. ↑ Inada, Yoshinobu; Tamiya, Naoki; Miyake, Maako; Morisaka, Tadamichi; Sakai, Mai; Wakabayashi, Ikuo; Kasamatsu, Masahiko; Uekusa, Yasuhiro (2017). "Fluid dynamic effects of small projections based on dorsal ridge tubercles of the finless porpoise". Journal of Biomechanical Science and Engineering. 12 (3): 16–00700–16-00700. doi: 10.1299/jbse.16-00700 .
  9. ↑ Yang, Jiwei; Wang, Kang; Mei, Zhigang; Xu, Jun; Zheng, Jinsong; Wan, Xiaoling; Hao, Yujiang; Wang, Kexiong; Wang, Ding (2021). "Temporal variation in the diet of Yangtze finless porpoise calls for conservation of semi-migratory fish". Freshwater Biology. 66 (5): 992–1001. doi:10.1111/fwb.13692. ISSN   0046-5070. S2CID   233796707.
  10. ↑ “Yangtze Finless Porpoise - River Dolphins.” River Dolphins - Protecting River Dolphins Worldwide, 9 July 2021, https://www.riverdolphins.org/river-dolphins-worldwide/yangtze-finless-porpoise/#reference-9.
  11. ↑ Mei, Zhigang; Huang, Shiang-Lin; Hao, Yujiang; Turvey, Samuel T.; Gong, Weiming; Wang, Ding (September 2012). "Accelerating population decline of Yangtze finless porpoise". Biological Conservation. 153: 192–200. doi:10.1016/j.biocon.2012.04.029.
  12. ↑ Wang, Zhi-Tao; Akamatsu, Tomonari; Duan, Peng-Xiang; Zhou, Lu; Yuan, Jing; Li, Jiao; Lei, Pei-Yu; Chen, Yu-Wei; Yang, Yi-Ning; Wang, Ke-Xiong; Wang, Ding (2020-07-01). "Underwater noise pollution in China's Yangtze River critically endangers Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis)". Environmental Pollution. 262: 114310. doi:10.1016/j.envpol.2020.114310. ISSN   0269-7491. PMID   32155559. S2CID   212667318.
  13. 1 2 3 Zheng, J. S.; Liao, X. L.; Tong, J. G.; Du, H. J.; Milinkovitch, M. C.; Wang, D. (August 2008). "Development and characterization of polymorphic microsatellite loci in the endangered Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis)". Conservation Genetics. 9 (4): 1007–1009. doi:10.1007/s10592-007-9435-7. S2CID   23622644.
  14. ↑ Kejia, Zhang (2007). "Poyang Lake: saving the finless porpoise" . Retrieved 19 November 2015.
  15. ↑ Yang, Fangxing; Zhang, Qinghua; Xu, Ying; Jiang, Guibin; Wang, Yawei; Wang, Ding (2008). "Preliminary hazard assessment of polychlorinated biphenyls, polybrominated diphenyl ethers, and polychlorinated dibenzo-p-dioxins and dibenzofurans to Yangtze finless porpoise in Dongting Lake, China". Environmental Toxicology and Chemistry. 27 (4): 991–996. doi:10.1897/07-381.1. PMID   18333690. S2CID   20715408.
  16. ↑ Chen S.. 2017. Water scheme threatens Yangtze River porpoises with extinction, scientist warns. South China Morning Post. Retrieved on September 28, 2017
  17. ↑ Hashimoto, Midori; Shirakihara, Kunio; Shirakihara, Miki; Hiramatsu, Kazuhiko (July 2013). "Estimating the rate of increase for the finless porpoise with special attention to predictions for the Inland Sea population in Japan". Population Ecology. 55 (3): 441–449. doi:10.1007/s10144-013-0374-5. S2CID   15843140.
  18. ↑ WWF Global (2012). "Yangtze River expedition points to decline of endangered finless porpoise". World Wildlife Fund. Retrieved 19 November 2015.
  19. ↑ "长江江豚家族再次"添丁"".
  20. ↑ "我市滨江公园水域出现长江江豚-南通市人民政府".
  21. ↑ Mei, Zhigang; Zhang, Xinqiao; Huang, Shiang-Lin; Zhao, Xiujiang; Hao, Yujiang; Zhang, Lin; Qian, Zhengyi; Zheng, Jinsong; Wang, Kexiong; Wang, Ding (April 2014). "The Yangtze finless porpoise: On an accelerating path to extinction?". Biological Conservation. 172: 117–123. doi:10.1016/j.biocon.2014.02.033.
  22. ↑ Shiguan, Zhuang. "Scientists Join Hands to Seek the Last Yangtze River Dolphin". Archived from the original on November 12, 2007. Retrieved 19 November 2015.
  23. ↑ Jin, Justin (2017). "REBIRTH ALONG CHINA'S YANGTZE RIVER". Archived from the original on 2017-09-02. Retrieved 1 January 2022.
  24. ↑ Krchnak, Karin (30 September 2014). "Saving the Finless Porpoise". World Wildlife Fund . Retrieved 25 October 2015.
  25. ↑ Wang, Ding; Hao, Yujiang; Wang, Kexiong; Zhao, Quingzhong; Chen, Daoquang; Wei, Zhuo; Zhang, Xianfeng (September 2005). "Aquatic Resource Conservation. The first Yangtze finless porpoise successfully born in captivity (4 pp)". Environmental Science and Pollution Research International. 12 (5): 247–250. doi:10.1065/espr2005.08.284. PMID   16206715. S2CID   37638759.
  26. ↑ Wang, D.; Hao, Y.; Wang, K.; Zhao, Q.; Chen, D.; Wei, Z.; Zhang, X. (2005). "Aquatic Resource Conservation. The first Yangtze finless porpoise successfully born in captivity". Environmental Science and Pollution Research International. 12 (5): 247–250. doi:10.1065/espr2005.08.284. PMID   16206715. S2CID   37638759.
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