TAXONOMY
Class: Actinopterygii (ray-finned fishes)
Order: Acipenseriformes (Sturgeons and paddlefishes)
Family:Polyodontidae Paddlefishes (Paddlefishes)
Genus/species: Polyodon spathula
GENERAL CHARACTERISTICS: Gray, shark-like body with a deeply forked tail and huge toothless mouth when feeding. Extended upper jaw (rostrum) flattened into paddleshape, accounts for 1/3 of total body length. Fins stiffer than those of teleost fishes. Heterocercal tail. Skeleton cartilaginous, skin tough, scales lacking. Max length 221 cm (87 inches); max weight 90.7 kg (200 pounds), average weight considerably less.
DISTRIBUTION/HABITAT: Rivers of central United States, especially Mississippi River and its tributaries. Prefers deep pools in large rivers where the current is slow; is highly mobile and has been known to travel more than 2,000 miles.
DIET IN THE WILD: Zooplankton, the majority being water fleas, also tiny crustaceans and larvae. To feed, the fish swims with its huge mouth wide open. As the water passes over its gills food is filtered out by special filaments called gill rakers. Also, the paddle is covered with pores that extend over the head and along the gill covers. These pores are electroreceptors capable of detecting as little as 1/100 of 1-millionth volt per cm, enough to sense the presence of plankton, a valuable tool, especially since vision, hearing and smell are poor.
REPRODUCTION and DEVELOPMENT: Female spawn only once every 4 to 7 years starting when they are 6-12 years old swimming up river to lay 2 eggs at a time. Egg cases rounded. Eggs hatch in 7 days; young are swept downstream to permanent home.
MORTALITY: Live up to 30 years.
PREDATORS: Only man.
CONSERVATION STATUS: IUCN: vulnerable. Threatened by overfishing throughout much of its range, particularly for its eggs since the ban on imported caviar. Dams prevent fish from reaching spawning grounds, sedimentation and river modifications destroy habitat.
REMARKS: The paddle is covered with pores that extend over the head and along the gill covers. These pores are electroreceptors capable of detecting as little as 1/100 of 1-millionth volt per cm, enough to sense the presence of plankton, a valuable tool, especially since vision, hearing and smell are poor.
Both paddlefish and sharks have skeletons made of cartilage, not bone. Paddlefish have no scales.
Paddlefish are the oldest surviving animal species in North America. Fossil records indicate that they date back 300 million years.
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