Chinese paddlefish

The Chinese paddlefish (Psephurus gladius) (simplified Chinese: 白鲟; traditional Chinese: 白鱘; pinyin: báixún), also known as Chinese swordfish, is a reportedly extinct species of fish that was native to the Yangtze and Yellow River basins in China. At maturity, the species measured an average length of 3 m (9.8 ft),[4] making it one of the largest species of primarily freshwater fishes. It was the only species in the genus Psephurus and one of two living species in the paddlefish family (Polyodontidae), the other being the American paddlefish (Polyodon spathula). It was an anadromous species, meaning that it spent part of its adult life at sea, while migrating upriver to spawn. Unlike its close relative, the Chinese paddlefish was largely piscivorous, and mainly preyed on small to medium-sized fish.

Chinese paddlefish

Critically endangered, possibly extinct  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Acipenseriformes
Family: Polyodontidae
Genus: Psephurus
Günther, 1873
Species:
P. gladius
Binomial name
Psephurus gladius
(von Martens, 1862)
Synonyms[2][3]
  • Polyodon gladius von Martens 1862
  • Spatularia (Polyodon) angustifolium Kaup 1862
  • Polyodon angustifolium (Kaup 1862)

Fishing of the Chinese paddlefish goes back centuries, with annual harvest reaching 25 tons by the 1970s. Since the 1990s, the species was officially listed by the International Union for Conservation of Nature (IUCN) as critically endangered, and was last seen alive in 2003. A 2019 paper from the Yangtze River Fisheries Research Institute reported its extinction, suggesting that it had gone extinct sometime between 2005 and 2010, but had been functionally extinct since 1993. It was unanimously agreed to be extinct by the Species Survival Commission Sturgeon Specialist Group of the IUCN on the 15th of September 2019.[5] It was stated that the IUCN Red List status would not be updated until June 2020,[6] but has not been updated as of January 2021.[7] The main cause of decline was the construction of the Gezhouba and Three Gorges dams, causing population fragmentation and blocking the anadromous spawning migration. Overfishing also played a significant role.

Description

The Chinese paddlefish had a white underbelly, and its back and head were grey, while extremities including the rostrum and the fins were pinkish red in colour. It had a pronounced white ridge along the sides of its body which extended from the middle of the body to the caudal fin. Its dorsal and anal fins were situated considerably far back on the body. The titular paddle was wedge-shaped with a triangular profile and was not flattened, as opposed to the rectangular, flattened profile of the American paddlefish's equivalent. The paddle was narrow and pointed, and could reach one third of total body length. Its eyes are small and round.[8] The teeth were noted to be small, and the jaw to be protrusible, unlike the American paddlefish. The tail fin was heterocercal, with a well developed caudal lobe. Like other members of Acipenseriformes the skeleton was cartilaginous and the body was smooth and largely lacking in scales, except for small scales in the caudal peduncle and caudal fin. It reached sexual maturity at a weight of around 25 kg (55 lb),[9] usually by the time the fish was age seven or eight, with a typical body length of 2 m (6 ft 7 in). Anecdotal reports indicate the Chinese paddlefish could reach 7 m (23 ft) in length and weigh up to 500 kg (1,100 lb),[10] or even several thousand pounds.[7] Limited research has been conducted on the species maximum size and weight as a result of its endangered status and lack of sightings over the years. A more generally accepted maximum size is 300 kg (660 lb) in weight and 3 m (10 ft) in length.[10]

Taxonomy
Scientific drawing of Psephurus galdius from 1868

Taxonomic history

The species was first named as a species of Polyodon by Eduard von Martens in 1862.[11] It was placed into a separate, monotypic genus by Albert Günther in 1873.[12] The species was also given a different name, Polyodon angustifolium by Johann Jakob Kaup also in 1862,[13] but this is considered a junior synonym of P. gladius.

Etymology

In Chinese this paddlefish is also called "elephant fish" (象魚; xiàngyú) because its snout vaguely resembles an elephant trunk. It is recorded sometimes in Classical Chinese as wěi-fish (鮪). More poetically, it is sometimes referred to as the "Giant Panda of the Rivers", not because of any physical resemblance to a giant panda, but because of its rarity and protected status. The origin of its binomial name comes from the Greek words pseph (pebble) and phoreus (bearer of), which when combined, also shares the meaning of the Greek word psepharos (gloomy/cloudy one).

Distribution, habitat and ecology
A specimen of Psephurus gladius exhibited in the Museum of Hydrobiological Sciences of Wuhan Institute of Hydrobiology

The Chinese paddlefish was native to the Yangtze (Chang Jiang) River basin and its estuary at the East China Sea. Historically it was also recorded in Yellow River basin (which is connected to the Yangtze by the Grand Canal) and its estuary at the Yellow Sea.[9][14][15]

Closeup of the tip of the paddle, showing sensory regions

The species spent part of its life in the lower section of the Yangtze, including the brackish water of its estuary, but migrated up river and into major tributaries to spawn, which occurred in Spring, from mid-March to early April.[1] It primarily inhabited the large rivers, but sometimes travelled into large lakes.[1] Due to their anadromous nature, mature individuals were found in coastal waters of the East China Sea and the Yellow Sea, occasionally spring tides would bring individuals into the lower reaches of the Qiantang and Yangjian rivers.

The fish was largely solitary, and occupied the lower-mid layers of the water column. It was noted for being a strong swimmer. Unlike its relative the American paddlefish, which is planktivorous, the Chinese paddlefish was primarily piscivorous, primarily feeding on small to medium-sized fishes like anchovies (Coilia), cyprinids (Coreius, Rhinogobio) and gobiids (Gobius) as well as bagrids and bothids, shrimp and crab were also eaten.[16] Research suggests that the American paddlefish uses electroreceptors located on the rostrum to detect prey.[17][18] Presumably, the Chinese paddlefish possessed similar abilities, though little research had been conducted on it due to its rarity.

Conservation status

The Chinese paddlefish has been listed as a first-level protected animal of the People's Republic of China since 1983 and on CITES Appendix II since 1998. The species was last sighted alive in 2003, and there was one anecdotal report of a dead specimen in 2007 but it was not until 2019 that the species was reported in a published study as extinct. Wei Qiwei with the Yangtze River Fisheries Research Institute, and co-author of a 2019 study published in the journal Science of the Total Environment reported the Chinese paddlefish extinct.[4][19][20] However, their official status will not be updated by the IUCN until June 2020.[6] The primary cause of its extinction was overfishing and the loss of critical habitat. Schooling young were easily caught by traditional fishing methods, therefore reducing sustainability of viable populations. Dams, notably the Gezhouba Dam and Three Gorges Dam, landlocked and divided populations, and prevented spawning migration.[1]

17th-century depiction

The last records of Chinese paddlefish in the Yellow River basin and its estuary date back to the 1960s, although declines were realized between the 13th and 19th centuries.[14][21][15] Declines were significant throughout its primary range in the Yangtze basin, but annual captures of 25 tonnes continued in 1970s. The species was still being found in small numbers in the 1980s (for example, 32 were caught in 1985) and young were seen as recently as 1995.[1]

Since 2000, there have only been two confirmed sightings of the fish alive, both from the Yangtze basin: The first was a 3.3-metre (11 ft), 117-kilogram (258 lb) female caught at Nanjing in 2002 and the second a 3.52-metre (11.5 ft), 160-kilogram (352 lb) female accidentally caught at Yibin, Sichuan on January 24, 2003 by fisherman Liu Longhua (刘龙华);[22] the former died despite attempts to save it and the latter was radio-tagged and released, but the tag stopped working after only 12 hours.[1][23]

During a search conducted in the Yangtze basin from 2006–2008, a research team from the Chinese Academy of Fisheries Science in Jingzhou failed to catch any paddlefish,[23] but two probable specimens were recorded with hydroacoustic signals.[24] Although very small numbers might survive,[1] many scientists now consider the Chinese paddlefish to be extinct.[25] A 2019 study reaffirmed the species as likely extinct following extensive capture surveys of the Yangtze between 2017 and 2018 that did not report any live specimens of the paddlefish. The paper estimated that the species went extinct between 2005 and 2010, and became functionally extinct by 1993. The study found the species' extinction to have been primarily caused by overfishing and habitat fragmentation, with one of the main contributors being the construction of the Gezhouba Dam in 1981. The paper thus recommended the reclassification of the species as Extinct by the IUCN.[21] Prof. Wei Qiwei (危起伟) with the Yangtze River Fisheries Research Institute, and a co-author of a 2019 study published in the journal Science of the Total Environment, reported the extinction of the Chinese paddlefish on CCTV.[4][19][20] However, their official Red List status will not be updated by the IUCN until June 2020.[6]

See also

References
  1. Qiwei, W. "Psephurus gladius". IUCN Red List of Threatened Species. 2010. Retrieved 3 January 2020.
  2. Froese, R.; Pauly, D. (2017). "Polydontidae". FishBase version (02/2017). Archived from the original on 24 August 2017. Retrieved 18 May 2017.
  3. "Polydontidae" (PDF). Deeplyfish- fishes of the world. Archived (PDF) from the original on 24 August 2017. Retrieved 18 May 2017.
  4. Yirka, Bob (2020-01-08). "Chinese paddlefish declared extinct". Phys.org. Retrieved 2020-01-09.
  5. "The Chinese paddlefish was reevaluated to be extinct". IUCN. Archived from the original on 2020-08-23.
  6. "IUCN statement on Chinese Paddlefish". Sina Weibo (in Chinese). 2020-01-03. Retrieved 8 January 2020.
  7. "Psephurus gladius". IUCN Red List of Threatened Species. 2010. 2010. Retrieved June 3, 2017.
  8. Gao, Xin; Wang, Jian Wei; Brosse, Sébastien (April 2009). "Threatened fishes of the world: Psephurus gladius (Martens, 1862) (Acipenseriformes: polyodontidae)". Environmental Biology of Fishes. 84 (4): 421–422. doi:10.1007/s10641-009-9443-1. ISSN 0378-1909. S2CID 38833459.
  9. "Species Fact Sheets: Psephurus gladius (Martens, 1862)". Food and Agricultural Organization of the United Nations. Archived from the original on 19 April 2012. Retrieved 1 February 2019.
  10. Froese, Rainer and Pauly, Daniel, eds. (2010). "Psephurus gladius" in FishBase. July 2010 version.
  11. Über einen neuen Polyodon aus dem Yantsekiang und über die sogenannten Glaspolypen. Monatsberichte der Königlichen Preussischen Akademie der Wissenschaften zu Berlin 1861 (pt. 1) (for 2 May 1861): 476-479.
  12. Günther, A. 1873: Report on a collection of fishes from China. Annals and Magazine of Natural History (Series 4) 12 (69): 239–250
  13. Kaup, J.J. 1862: Eine neue Art von Spatularia. Archiv für Naturgeschichte 28 (1): 278–281
  14. Xie, J.Y.; W.J. Tang; Y.H. Yang (2018). "Fish assemblage changes over half a century in the Yellow River, China". Ecology and Evolution. 8 (8): 4173–4182. doi:10.1002/ece3.3890. PMC 5916296. PMID 29721289.
  15. Li, S.Z. (2015). Fishes of the Yellow River and Beyond. The Sueichan Press. pp. 61–63. ISBN 9789578596771.
  16. Chenhan, Liu; Yongjun, Zeng (1988-05-18). "Notes on the Chinese Paddlefish, Psephurus gladius (Martens)". Copeia. 1988 (2): 482. doi:10.2307/1445891. JSTOR 1445891.
  17. Neiman, Alexander B.; Russell, David F.; Pei, Xing; Wojtenek, Winfried; Twitty, Jennifer; Simonotto, Enrico; Wettring, Barbara A.; Wagner, Eva; Wilkens, Lon A.; Moss, Frank (November 2000). "Stochastic Synchronization of Electroreceptors in Paddlefish". International Journal of Bifurcation and Chaos. 10 (11): 2499–2517. Bibcode:2000IJBC...10.2499N. doi:10.1142/S0218127400001717. ISSN 0218-1274.
  18. Wilkens, Lon A.; Hofmann, Michael H. (2007-05-01). "The Paddlefish Rostrum as an Electrosensory Organ: A Novel Adaptation for Plankton Feeding". BioScience. 57 (5): 399–407. doi:10.1641/B570505. ISSN 1525-3244.
  19. Cheung, Eric (2020-01-07). "Up to 23 feet long, the Chinese paddlefish was the giant of the Yangtze. And we killed it". CNN. Retrieved 2020-01-09.
  20. "Chinese paddlefish, one of world's largest fish, declared extinct". Animals. 2020-01-08. Retrieved 2020-01-09.
  21. Zhang, Hui; Jarić, Ivan; Roberts, David L.; He, Yongfeng; Du, Hao; Wu, Jinming; Wang, Chengyou; Wei, Qiwei (2020). "Extinction of one of the world's largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna". Science of the Total Environment. 710: 136242. Bibcode:2020ScTEn.710m6242Z. doi:10.1016/j.scitotenv.2019.136242. ISSN 0048-9697. PMID 31911255.
  22. ""最后的长江白鲟"目击者：3.52米长 160公斤重 消失在宜宾江水中……-新华网". www.xinhuanet.com. Retrieved 2020-01-09.
  23. Bourton, Jody (2009-09-29). "Giant fish 'verges on extinction'". BBC News. London: BBC. Archived from the original on 2012-04-19. Retrieved 2009-09-29.
  24. Zhang; Wei1, Q.W.; Du, H.; Shen, L.; Li, Y.H.; and Zhao, Y. (2009). Is there evidence that the Chinese paddlefish (Psephurus gladius) still survives in the upper Yangtze River? Concerns inferred from hydroacoustic and capture surveys, 2006–2008. Journal of Applied Ichthyology 25(s2): 95-99. DOI: 10.1111/j.1439-0426.2009.01268.x.
  25. "14 Animals Declared Extinct - Chinese Paddlefish". Christian Science Monitor. 2015-10-22. Archived from the original on 20 November 2016. Retrieved 20 January 2017.

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