Wednesday, December 15, 2010

December 15, 2010 : Paddlefish


Paddlefish (family Polyodontidae) are primitive Chondrostean ray-finned fishes. The paddlefish can be distinguished by its large mouth and its elongated snout called a rostrum (gill). These spatula-like snouts comprise half the length of their entire body. There are only two extant species of these fish: the Chinese and the American paddlefish. In some areas, paddlefish are referred to as "Spoonbill", "Spoonies" or "Spoonbill Catfish". The American species is Missouri's State Aquatic Animal.

These fish are not closely related to sharks, which are in a different class, but they do have some body parts that resemble those of sharks such as their skeletons, primarily composed of cartilage, and deeply forked heterocercal tail fins.

The Chinese paddlefish (Psephurus gladius) lives in the Yangtze River. 9' (3-meter) specimens weighing 300 kilograms (660 lb) have been recorded; reports of 7 metres (23 ft) fish exist, although the existence of such large specimens is doubtful. They are said to now be extinct, with a recently completed three-year survey of the Yangtze finding no specimens.

The American paddlefish (Polyodon spathula) lives in the slow-flowing waters of the Mississippi River, Missouri River, Des Moines River, Yellowstone River, Ohio River, Wisconsin River, and Arkansas River systems (and was historically found in the Great Lakes). In May 2000, the Canadian Species at Risk Act listed the Paddlefish as being extirpated in Canada. The American paddlefish is one of the largest freshwater fish in North America. They commonly reach 5 feet (1.5 m) or more in length and can weigh more than 60 pounds (27 kg). The largest American paddlefish on record was caught in Kansas and weighed 144 pounds (65 kg), by Clinton Boldridge out of Atchison Watershed. The largest unofficial record was 206 pounds from Lake Cumberland in Kentucky. Postcards from the 1960s show a photo of this huge fish. This type of fish's age is hard to determine but many scientists think that they live 50 years or more.

Fossils of other paddlefish have been found. One such species is Crossopholis magnicaudatus. C. magnicaudatus has been found in the Green River Shale deposit of Wyoming and dates to the Eocene.

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