Species Fact Profile: American Paddlefish (Polyodon spathula)

American Paddlefish

Polyodon spathula (Walbaum, 1792)

Range: Mississippi River Basin (Central United States)
Habitat: Deep, Slow-Moving Rivers, Lakes, Occasionally in Brackish Water
Diet: Zooplankton
Social Grouping: Aggregations for Mating
Reproduction: Spawn every 2-3 years, based on environmental stimuli (photoperiod, water levels, temperature).  Gather in breeding schools.  Multiple males swim around eggs and release milt.  Eggs are deposited on sandbars.  Larval hatchlings are carried downstream by river currents.  Once gill rakers form, they can begin filter feeding.  Mature at t-14 years old
Lifespan: 20-30 Years, up to 55 years
Conservation Status: IUCN Vulnerable, CITES Appendix II

• Body length up to 2.5 meters, but usually 1.5 meters.  Weight 18-70 kilograms, males generally larger than females.  
• Very smooth, almost scaleless skin is gray or black on the back and sides with some mottling, paling to white on the underbelly
• Distinguishable for all other North American fish by its paddle-like extended snout.  This paddle is a highly-sensitive attenuate covered with electro-receptors, used to find prey and help navigate during migration
• Feed by swimming with their large mouths wide open.  Strains its prey out of the water using large, fine gill-rakers, feeding while ventilating their gills at the same time
• Generally stay within home range, but may travel during breeding season, have been known to travel up to 2000 miles through the river system
• Dam construction has isolated or extirpated many populations, preventing dispersal.  Believed to be extirpated from the Great Lakes
• Once one of the most commercially harvested fish in the Mississippi River system for their meat and their eggs, causing population to decline.  Exploitation increased after the crash of sturgeon populations in Europe led to increased (often illegal) harvesting of paddlefish for their eggs as a substitute caviar 
• Raised on fish farms, both in the US and in Europe.   Introduced to the Flint River system in Georgia after about 1200 individuals escaped from an aquaculture facility.  Have also been introduced to the Balkans as a sports fish
• Despite their very simple immune system, they seemingly never get cancer due to their cartilaginous skeletons, making them important research models