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Concept
Paddlefish
Summary
Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their elongated rostra, which are thought to enhance electroreception to detect prey. Paddlefish have been referred to as "primitive fish" because the Acipenseriformes are among the earliest diverging lineages of ray-finned fish, having diverged from all other living groups over 300 million years ago. Paddlefish are almost exclusively North American and Chinese, both extant and in the fossil record.
Eight species are known - six extinct species known only from fossil remains (five from North America, one from China), one extant species, the American paddlefish (Polyodon spathula), which is native to the Mississippi River basin in the U.S., and the Chinese paddlefish (Psephurus gladius), declared extinct in 2022 following a 2019 recommendation that it be declared extinct. The species was last sighted in 2003 in the Yangtze River Basin in China. Chinese paddlefish are also commonly referred to as "Chinese swordfish", or "elephant fish". The earliest known species is Protopsephurus from the Early Cretaceous (Aptian) of China, dating to around 120 million years ago.
Paddlefish populations have declined dramatically throughout their historic range as a result of overfishing, pollution, and the encroachment of human development, including the construction of dams that have blocked their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed natural flows resulting in the loss of spawning habitat and nursery areas.
Paddlefish as a group are one of the few organisms that retain a notochord past the embryonic stage. Paddlefish have very few bones and their bodies mostly consist of cartilage with the notochord functioning as a soft spine. During the initial stages of development from embryo to fry, paddlefish have no rostrum (snout).
Official source
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