American paddlefish

Water parameters

Minimum tank: 5000 L per individual at harvest size.

Feed and growth

Feed protein

35% target

Daily feed (warm)

1.50% of body weight

Daily feed (cool)

0.50% of body weight

Max density

15 g per litre

A 90000 g adult eats about 1350.0 g of feed per day at optimum. 10 fish at adult size: ~13500 g daily.

Legality

Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.

Unlisted jurisdictions default to "check local regulations".

Origin and habitat

The last living species of paddlefish (family Polyodontidae); the Chinese paddlefish (Psephurus gladius) of the Yangtze was declared extinct. Most closely related to sturgeons; together they form the order Acipenseriformes, one of the most basal living groups of ray-finned fish. Fossil records of paddlefish date back roughly 125 million years to the Early Cretaceous; records of Polyodon extend back 65 million years to the early Paleocene. Native range: Mississippi River basin from southwestern New York to central Montana and south to Louisiana, plus Gulf Slope drainages from Mobile Bay, Alabama to Galveston Bay, Texas; formerly also in the Lake Erie drainage. Currently found in 22 US states; range has been reduced by dams that disrupt migratory spawning. The elongated paddle-shaped rostrum (up to one-third of body length) is a sensory array with tens of thousands of electrosensory ampullae that detect weak bioelectric fields of zooplankton prey. A ram-filtering planktivore that strains zooplankton using gill rakers while swimming with mouth open. Can grow to roughly 220 cm (7 feet) and weigh up to 90 kg (almost 200 lbs). Lifespan potentially 60 years or more. Listed as CITES Appendix II since 1992 due to concerns about illegal poaching for caviar. Paddlefish roe is processed into caviar comparable to Caspian sevruga sturgeon caviar. Aquaculture is in research and developmental phase; larvae are raised in zooplankton-rich ponds, then trained on extruded trout/salmon diets once juveniles exceed 30 cm. Also cultured in Russia, Romania, and other European countries in polyculture with carp.

Climate and outdoor ponds

Climate

temperate (handles seasonal swings)

USDA zones

4–9 (winter low around -34°C or warmer)

Heating needed

no

Cooling needed

no

Care notes

A specialty aquaculture species grown primarily for caviar, not a typical aquaponics candidate. Paddlefish require large volumes of water (ponds or very large tanks, 5000 L minimum) because they're continuous swimmers that don't tolerate confinement well. In the wild they are obligate filter feeders straining zooplankton. In culture, larvae are initially raised in fertilized ponds supporting dense zooplankton populations (primarily Daphnia). Juveniles can then be trained to accept extruded trout or salmon pellet feeds once they exceed roughly 30 cm total length. This training process takes several weeks and not all individuals accept pellets. Water temperature tolerance is broad (roughly 4–28°C), with optimal growth at 20–25°C. Dissolved oxygen above 5 mg/L. Growth to caviar-harvest size takes 7-10 years for females (males don't produce roe). The long maturation time and specialized requirements make paddlefish impractical for most aquaponics setups. They're included here for operators of large pond-based systems who want a high-value specialty product. Fingerlings are available from state hatcheries in several Mississippi basin states. Legal status varies by state; many restrict paddlefish culture to protect wild populations, and CITES Appendix II listing requires export permits for international trade.

Further reading

• Aquaponics water chemistry: balancing pH for fish and plants
• Fish for aquaponics: tilapia vs everything else