American paddlefish (Polyodon spathula)
American paddlefish are basal chondrostean ray-finned fish closely related to sturgeons in the order Acipenseriformes. American paddlefish are one of only two extant taxa in the paddlefish family, Polyodontidae. The other is the critically endangered Chinese paddlefish which may now be extinct. American paddlefish are highly derived with adaptations specifically for filter feeding. Their rostrum and cranium are covered with tens of thousands of sensory receptors for locating swarms of zooplankton which is their primary food source. American paddlefish are endemic to the Mississippi River Basin. They commonly inhabited large, free-flowing rivers, braided channels, backwaters and oxbow lakes. American paddlefish are among the largest and longest lived freshwater fishes in North America. They have a shark-like body with an average 1.5 metres in length. American paddlefish populations have declined dramatically primarily as a result of overfishing and habitat destruction. In 2004 they were listed as Vulnerable on the IUCN Red List of Threatened Species.
photo credits: wiki, blickwinkel/Alamy, scienceforums
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