Chinese paddlefish

The Chinese paddlefish had a white underbelly, and its back and head were grey. Its eyes were small and round. The tail fin was heterocercal (spine extending into the upper lobe), with the lower lobe being well developed. The teeth were small, sharp, canine shaped and inward curling, and became proportionally smaller relative to the jaw during growth, and in mature adults were completely fused into the bone. Compared to Polyodon, the jaws were shorter, and had a proportionately narrower gape, and unlike the American paddlefish, but similar to fossil paddlefish, the upper jaw was not firmly attached to the braincase. The body lacked scales,The maximum length of the Chinese paddlefish is often quoted as , with this estimate apparently being given by C. Ping (1931) as quoted by John Treadwell Nichols in 1943, though according to Lance Grande and William Bemis in 1991, the Chinese paddlefish was only definitively known to have body lengths in excess of . However, Grande and Bemis (1991) suggested that this enormous length may have been the result of a translation error. 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. == Taxonomy and evolutionary history ==

'') The species was first named as a species of Polyodon (the genus of the American paddlefish) 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, Spatularia angustifolium by Johann Jakob Kaup also in 1862, but this is considered a junior synonym of P. gladius. The oldest representatives of the genus containing the American paddlefish, Polyodon date to around 65 million years ago, from the beginning of the Paleocene. Various molecular clock estimates have been given for the age of the divergence between the American and Chinese paddlefish, including 68 million years ago 72 million years ago, and 100 million years ago, all dating to the middle to Upper Cretaceous. Relationships of recent and fossil paddlefish genera, after Grande et al. (2002). ==Distribution, habitat and ecology==

|thumb|left 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 the Yellow River basin (which is connected to the Yangtze by the Grand Canal) and its estuary at the Yellow Sea. They were also historically 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 Yong rivers of Zhejiang province. The ovaries of the female fish contained over 100,000 eggs, each approximately across, |alt= The fish was largely solitary, and occupied the lower-mid layers of the water column. Chinese paddlefish were noted for being strong swimmers. Unlike its relative the American paddlefish, which is a planktivorous filter feeder, the Chinese paddlefish was primarily piscivorous, mainly feeding on small to medium-sized fishes like anchovies (Coilia), cyprinids (Coreius, Rhinogobio), gobies (Gobius) as well as bagrid catfish and bothid flounders. It also consumed crustaceans like shrimp and crabs. 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. 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. ==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. Declines were significant throughout its primary range in the Yangtze basin, but annual captures of 25 tonnes continued into the 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. 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 to 2008, a research team from the Chinese Academy of Fisheries Science in Jingzhou failed to catch any paddlefish, 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, but became functionally extinct by 1993. The paper thus recommended the reclassification of the species as Extinct by the IUCN. A similar recommendation was also made by the Species Survival Commission Sturgeon Specialist Group of the IUCN in September 2019. The official IUCN status of the species was formally updated to "extinct" in July 2022. The primary cause of its extinction was the construction of the Gezhouba Dam, which became operational 1981, which a 2024 study described as having "sealed its fate of inevitable extinction" upon becoming operational because it effectively prevented the fish from properly completing its life cycle, dividing the fish population into subadults downstream of the dam who could not migrate upriver through the dams turbines to reproduce, and a residual adult population upstream of the dam who could continue to spawn but not effectively replace itself over the long term. Overfishing also played a role in its decline. The Chinese 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. == Cultural significance ==

A gold belt from the Jinsha site in Sichuan, dating to around 1000 BC, has been found emblazoned with drawings of what is suggested to be Chinese paddlefish. The Classic of Poetry (11th to 7th century BC) may contain references to the Chinese paddlefish as one of the animals sacrificed during rituals. The Huainanzi (2nd century BC) claims that the fish was receptive to rhythm and attracted to the sound of musical instruments. The Eastern Jin writer Guo Pu apparently mentions the fish in his work Jiang Fu (江賦, lit. Ode to the River). The 9th century Tang dynasty book Miscellaneous Morsels from Youyang suggests that killing a Chinese paddlefish could cause rain. The fish is depicted in a number of historical Chinese paintings. Sichuanese fishermen had a saying regarding the fish, referencing its large size. Some common names for the fish in Chinese compare the rostrum of the fish to an elephant's trunk. Like the related sturgeons and American paddlefish, the species was fished for its caviar, though it made up only a small proportion (less than 1%) of the total number of fish caught from the Yangtze in the late 20th century by weight. ==See also==