American paddlefish

Quick facts

Adult size

120 cm, 20000 g typical harvest weight

Days to harvest

2555 to 3650 days from fingerling

Lifespan (max)

up to 55 years

Diet

omnivore

Temperature class

cool-water

Difficulty

advanced

Water parameters

Temperature range

4–28°C (optimum 20°C)

pH

6.5 to 8

Hardness

5 to 20 dGH

Minimum tank

5000 L per individual at harvest size

Feed and growth

Feed protein

35% target

Daily feed (warm water)

1.50% of body weight per day

Daily feed (cool water)

0.50% of body weight per day

Max stocking density

15 g per litre of system water

A 20000g adult eats about 300.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 3000 g of feed daily.

Legality

Aquaculture and possession rules vary by jurisdiction and change over time. This table reflects regulations as of the verified date on each row. Verify with your local fisheries or wildlife authority before stocking.

Jurisdictions not listed here default to "check local regulations". A non-listing is not a green light; rules in your specific county or municipality may apply.

Habitat and origin

Native to the Mississippi River basin and associated tributaries across the central United States. The species (Polyodon spathula) is one of only two living paddlefish species (the other, the Chinese paddlefish, was declared extinct in 2020). A primitive fish related to sturgeons, with a distinctive elongated rostrum (paddle-shaped snout) that functions as an electrosensory organ to detect zooplankton. In the wild, paddlefish are filter feeders that swim with their mouths open, straining zooplankton from the water column. Adults can reach 2 m and 60 kg, though culture specimens are harvested much smaller. The primary aquaculture interest is caviar production: paddlefish roe is sold as a domestic alternative to Caspian sturgeon caviar at premium prices ($200-500/kg).

Climate and outdoor ponds

Climate classification

temperate (handles seasonal swings)

Outdoor pond zones (USDA)

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

Heating in a temperate climate

Not required (handles seasonal cool periods)

Cooling in a temperate climate

Not required

Zone bounds reflect year-round outdoor pond viability with no active heating. Anywhere outside the bounded zone, the species can still be kept in an indoor heated tank or a seasonally-managed system. Verify your specific microclimate, as a sheltered yard zone can run a half-zone warmer than the regional rating.

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. They cannot be trained to eat pelleted feed in the traditional sense because they're obligate filter feeders; they strain zooplankton and suspended particles from the water. In pond culture, paddlefish are stocked in fertilized ponds that support dense zooplankton populations. In tank-based systems, they can be maintained on a diet of brine shrimp, daphnia, or specially designed liquid/suspended feeds, but this is expensive and labor-intensive. Water temperature range is 10–28°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 feeding requirements make paddlefish impractical for most aquaponics setups. They're included here for completeness and 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; some states restrict paddlefish culture to protect wild populations.

Further reading

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