Chinese paddlefish
The Chinese paddlefish , 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, 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, the other being the American paddlefish. 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.
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 as critically endangered, and has not been seen alive since 2003. A 2019 paper from the Yangtze River Fisheries Research Institute reported their extinction, suggesting that they had gone extinct sometime between 2005 and 2010, but had been functionally extinct since 1993. The official IUCN Red List status will not be updated until June 2020. 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 has a white underbelly, and its back and head are grey, while extremities including the rostrum and the fins are pinkish red in colour. It has a pronounced white ridge along the sides of its body which extends from the middle of the body to the caudal fin. Its dorsal and anal fins are situated considerably far back on the body. The titular paddle is wedge-shaped with a triangular profile and is not flattened, as opposed to the rectangular, flattened profile of the american paddlefish's equivalent. The paddle is narrow and pointed, and can reach one third of total body length. Its eyes are small and round. The teeth are noted to be small, and the jaw to be protrusible, unlike the American paddlefish. The tail fin is heterocercal, with a well developed caudal lobe. Like other members of Acipenseriformes the skeleton is cartilaginous and the body is smooth and largely lacking in scales, except for small scales in the caudal peduncle and caudal fin. They reach sexual maturity at a weight of around, usually by the time they are age seven or eight, with a typical body length of. Anecdotal reports indicate the Chinese paddlefish can reach in length and weigh up to, or even several thousand pounds. 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 in weight and in length.Taxonomy
Taxonomic history
The species was first named as a species of Polyodon by Eduard von Martens in 1862. It was placed into a separate, monotypic genus by Albert Günther in 1873. The species was also given a different name, Polyodon angustifolium by Johann Jakob Kaup also in 1862, but this is considered a junior synonym of P. gladius.Etymology
In Chinese this paddlefish is also called "elephant fish" because its snout vaguely resembles an elephant trunk. It is recorded sometimes in Classical Chinese as wěi-fish. 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 and phoreus, which when combined, also shares the meaning of the Greek word psepharos.Distribution, habitat and ecology
The Chinese paddlefish was native to the Yangtze River basin and its estuary at the East China Sea. Historically it was also recorded in Yellow River basin and its estuary at the Yellow Sea.Chinese paddlefish spent part of their 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. They primarily inhabited the large rivers, but sometimes travelled into large lakes. 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.
These fishes were largely solitary, and occupied the lower-mid layers of the water column. They were noted for being strong swimmers. 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 , cyprinids and gobiids '' as well as bagrids and bothids, shrimp and crab were also eaten. Research suggests that the American paddlefish uses electroreceptors located on the rostrum to detect prey. 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. However, their official status will not be updated by the IUCN until June 2020. 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.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. 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 and young were seen as recently as 1995.
Since 2000, there have only been two confirmed sightings of the fish alive, both from the Yangtze basin: The first was a, female caught at Nanjing in 2002 and the second a, 160-kilogram female accidentally caught at Yibin, Sichuan on January 24, 2003 by fisherman Liu Longhua ; 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.
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, but two probable specimens were recorded with hydroacoustic signals. Although very small numbers might survive, many scientists now consider the Chinese paddlefish to be extinct. 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. Prof. Wei Qiwei 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. However, their official Red List status will not be updated by the IUCN until June 2020.