Chinese paddlefish

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Chinese paddlefish
Preserved specimens at Museum of Hydrobiological Sciences, Institute of Hydrobiology, Wuhan, China

Extinct (2022)  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
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)

The Chinese paddlefish (Psephurus gladius;

anadromous species, meaning that it spent part of its adult life at sea, while migrating upriver to spawn
.

The Chinese paddlefish was officially declared extinct in 2022, with an estimated time of extinction to be by 2005, and no later than 2010, although it had become

critically endangered, and was last seen alive in 2003. A 2019 paper including scientists from the Yangtze River Fisheries Research Institute found the species to be extinct.[4] It was unanimously agreed to be extinct by the Species Survival Commission Sturgeon Specialist Group of the IUCN on 15 September 2019,[5] with its conservation status being formally updated by the IUCN Red List in July 2022.[6]

Description

Wuhan Institute of Hydrobiology

The Chinese paddlefish had a white underbelly, and its back and head were grey.

caudal peduncle and caudal fin.[8]

Juveniles attained a weight of around 1 to 1.5 kilograms (2 to 3 lb) by their first winter and a length of 1 m (3 ft) and a weight of about 3.3 kg (7 lb 4 oz) by the time they were a year old. Beyond this length, proportional weight gain relative to body length dramatically increased, reaching a weight of about 12.5 kg (28 lb) by the time they were around 1.5 m (5 ft) long. They reached sexual maturity at a weight of around 25 kg (55 lb).[11] The maximum length of the Chinese paddlefish is often quoted as 7 m (23 ft), with this estimate apparently being given by C. Ping (1931), though according to Grande and Bemis (1991), specimens over three metres (ten feet) had not been definitively measured.[9] Ping recorded that fishermen in Nanjing caught a Chinese paddlefish with a length of 7 metres (23 ft) and a weight of 907 kilograms (2,000 lb).[12] FishBase and World Wide Fund for Nature gives a conservative maximum weight of 300–500 kg (660–1,100 lb).[13][14] Female fish are suggested to have grown larger than male fish once sexually mature, though they grew at similar rates prior to this.[15] The lifespan has been estimated at 29–38 years, though the theoretical maximum lifespan is likely to have been significantly higher, as the estimate reflects anthropogenic impacts on the population.[4]

Taxonomy and evolutionary history

Scientific drawing of Psephurus gladius from 1868 (resource: Nouvelles Archives du Muséum national d'histoire naturelle)

The species was first named as a species of

Polyodon by Eduard von Martens in 1862.[16] It was placed into a separate, monotypic genus by Albert Günther in 1873.[17] The species was also given a different name, Spatularia angustifolium by Johann Jakob Kaup also in 1862,[18] but this is considered a junior synonym of P. gladius.[8]

Upper Cretaceous
.

Relationships of recent and fossil paddlefish genera, after Grande et al. (2002).[19]

Polyodontidae
Polyodontinae

†Psephurus

†Crossopholis

Polyodon

Distribution, habitat and ecology

Wuhan Institute of Hydrobiology

The Chinese paddlefish was native to the

Qiantang and Yong rivers of Zhejiang province.[11]

The species spent part of its life in the lower section of the Yangtze, including the

tributaries to congregate for spawning, which occurred in spring, from mid-March to early April. One spawning site on the Jinsha River, located at the midpoint of the river, around 60 m (200 ft) from the riverbank, was around 500 m (1,600 ft) in length, and had a max water depth of 10 m (33 ft) and rapid water flow, with the bottom sediments in the lower reaches being shingly and in the upper reaches muddy/sandy.[11] A study on a sample of spawning Chinese paddlefish found that they were all at least 8 years old.[26] Females likely sexually matured later than males, and probably did not spawn every year, likely every other year or somewhat less frequently, like other acipenseriforms.[27] The ovaries of the female fish contained over 100,000 eggs, each approximately 2.7 mm (3⁄32 in) across. The developing zygotes and fry were restricted to the region of the Yangtze basin upstream of Luzhou in southeastern Sichuan, while yearlings and adults were widely distributed throughout the Yangtze river proper from the lower to upper reaches.[11]

Closeup of the tip of the rostrum, showing electrorecepting ampullae

The fish was largely solitary, and occupied the lower-mid layers of the

protrusion, a form of cranial kinesis allowing them to move relative to the rest of the skull, with the upper jaw being able to thrust downwards and forwards in order to seize prey.[9][28] Paddlefish, like other Acipenseriformes and several other groups of vertebrates, engage in passive electroreception (the sensing of external electric fields) using structures called ampullae that form an extension of the lateral line system of sensory organs. Passive electroreception (where electric fields are sensed but not generated, as in electric fish) is primarily used for detecting the weak electric fields generated by prey.[29] The head and rostrum of Chinese paddlefish, like those of other paddlefish, was densely packed with ampullae, indicating that enhancing electroreception was one of the rostrum's primary functions.[9]

Decline and extinction

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.[24][25][30] Declines were significant throughout its primary range in the Yangtze basin, but annual captures of 25 tonnes continued into the 1970s.[4] In 1983, the Chinese government made fishing of the species illegal due to its decline in numbers.[26] 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] Due to the rarity of the fish by the time it was realised that it was in peril, and the fact that the adult fish were difficult to keep in captivity, attempts to create a captive breeding stock failed.[26]

Depiction in the 17th-century work Searching the Mountains for Demons by Zheng Zhong

Since 2000, there have been only two confirmed sightings of the fish alive, both from the Yangtze basin: The first was a 3.3-metre (10 ft 10 in), 117-kilogram (258 lb) female caught at Nanjing in 2002 and the second a 3.52-metre (11 ft 7 in), 160 kg (350 lb) female accidentally caught at Yibin, Sichuan, on January 24, 2003, by fisherman Liu Longhua (刘龙华);[31] 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][32]

During a search conducted in the Yangtze basin from 2006 to 2008, a research team from the

hydroacoustic signals.[33] A comprehensive study published in 2019, including scientists from the Yangtze River Fisheries Research Institute, found that the species was certainly extinct, based on its absence from extensive capture surveys of the Yangtze between 2017 and 2018. The paper estimated that the species went extinct between 2005 and 2010, and became functionally extinct by 1993.[4][34][35][36] The primary cause of its extinction was overfishing and the construction of dams along the Yangtze. The paddlefish was heavily overfished in all stages of growth from fry (which were easily captured by traditional fishing methods) to adult, which combined with the long generation time due to its slow maturation led to reduced sustainability of viable populations. Dam construction, notably the Gezhouba Dam, which became operational in 1981, and the Three Gorges Dam landlocked and divided populations and prevented the spawning migration.[1] The paper thus recommended the reclassification of the species as Extinct by the IUCN.[30] A similar recommendation was also made by the Species Survival Commission Sturgeon Specialist Group of the IUCN in September 2019.[5]

The official IUCN status of the species was formally updated to "extinct" in July 2022.[6][1]

See also

References

  1. ^
    doi:10.2305/IUCN.UK.2022-2.RLTS.T18428A146104283.en
    . Retrieved 21 July 2022.
  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. ^
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  5. ^ a b "The Chinese paddlefish was reevaluated to be extinct". IUCN. September 2019. Archived from the original on 23 August 2020.
  6. ^ a b Master, Farah; Zhang, Albee (22 July 2022). Fullick, Neil (ed.). "Chinese Paddlefish and wild Yangtze Sturgeon extinct - IUCN". Reuters. Archived from the original on 23 July 2022. Retrieved 22 July 2022.
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  8. ^ a b c d e f "Species Fact Sheets: Psephurus gladius (Martens, 1862)". Food and Agricultural Organization of the United Nations. Archived from the original on 3 October 2009. Retrieved 1 February 2019.{{cite web}}: CS1 maint: unfit URL (link)
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    from the original on 25 July 2022, retrieved 22 July 2022
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    JSTOR 1445891
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  12. ^ Contributions from the Biological Laboratory of the Science Society of China: Zoological series. Vol. 7. 1931. p. 189.
  13. ^ Froese, Rainer; Pauly, Daniel (eds.) (2010). "Psephurus gladius" in FishBase. July 2010 version.
  14. ^ "River of Giants: Giant Fish of the Mekong" (PDF). WWF for Nature. 2012.
  15. ^ J. Ma, Z. Deng, X. Deng, M. Cai Age determination and growth of Chinese paddlefish Psephurus gladius Acta Hydrobiologica Sinica, 20 (2) (1996), pp. 150–159 (in Chinese with English abstract)
  16. ^ "Über einen neuen Polyodon aus dem Yantsekiang und über die sogenannten Glaspolypen". Monatsberichte der Königlichen Preussischen Akademie der Wissenschaften zu Berlin. 1861 (pt. 1): 476–479. 2 May 1861. Retrieved 29 July 2022.
  17. doi:10.1080/00222937308680749
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  18. ^ Kaup, J.J. (1862). "Eine neue Art von Spatularia". Archiv für Naturgeschichte. 28 (1): 278–281.
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  28. ISBN 978-0-7923-4517-6
    . Retrieved 27 July 2022. Living sturgeons and primitive paddlefishes (i.e.,polyodontids other than Polyodon) stand in sharpcontrast to all of these outgroup taxa. Their jaws are highly mobile, so that the upper jaw can be 'projected' far out to capture prey...
  29. S2CID 73442571
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    S2CID 210086307
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  32. ^ a b Bourton, Jody (29 September 2009). "Giant fish 'verges on extinction'". BBC News. London: BBC. Archived from the original on 31 May 2012. Retrieved 29 September 2009.
  33. ^ 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.
  34. ^ Yirka, Bob (8 January 2020). "Chinese paddlefish declared extinct". Phys.org. Archived from the original on 8 January 2020. Retrieved 9 January 2020.
  35. ^ Cheung, Eric (7 January 2020). "Up to 23 feet long, the Chinese paddlefish was the giant of the Yangtze. And we killed it". CNN. Archived from the original on 9 January 2020. Retrieved 9 January 2020.
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External links

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