Paddlefish

Polyodon spathula

Family: Polyodontidae | Genus: Polyodon

Freshwater | Filter feeder (planktivorous) | Long-lived: up to 55 years | North America | Up to 221 cm

The Mississippi paddlefish (Polyodon spathula) is a large freshwater species native to North America, notable for its long lifespan and its distinctive spoon-shaped snout. This species commonly reaches around 120 cm in length, though the largest recorded individual measured 221 cm and weighed 90.7 kg. Adult paddlefish are  toothless, as their mouths are adapted to filter-feeding on plankton — although juveniles do possess numerous small teeth. The paddlefish is considered a living fossil, retaining many primitive anatomical traits from ancient fish lineages.

Geographical distribution

The paddlefish inhabits the extensive Mississippi River basin, ranging from south-western New York to Montana and southern Louisiana.
It is also found in Gulf Coast drainages, from Mobile Bay in Alabama to Galveston Bay in Texas (USA). Although it once had a much broader distribution, it is now restricted to these areas due to habitat degradation and river modification.

Habitat

This species prefers deep freshwater environments such as large, slow-moving rivers, lakes, and reservoirs. Some of its habitat characteristics are:

Depth: commonly found at depths greater than 1.2 m.
Slow currents: requires calm waters for efficient plankton filtration.
Demersal zones: lives mostly near the bottom, though it feeds throughout the water column.
Large river systems: highly sensitive to habitat fragmentation caused by dams and other artificial barriers.
Plankton-rich freshwater environments: the abundance of plankton is crucial for feeding and survival, making biological productivity a key factor.

Lifestyle and behaviour

The paddlefish is a specialised filter feeder with an extended upper jaw that helps channel plankton towards the mouth.

Social behaviour

They are non-territorial, it typically moves alone or in loose groups, particularly during spawning migrations.
A single female may spawn with several males throughout the breeding season.
It can live for up to 55 years, making it one of North America’s longest-lived freshwater fish species.

Reproduction

Oviparous species with a highly specific reproductive cycle.
Spawning occurs every 2–3 years, mainly in  spring, coinciding with river flooding.
The embryos develop a notochord (a primitive backbone) within 24 hours, and hatch after five days.
Adults migrate upstream to spawn on gravel banks, relying on suitable environmental conditions.
Females lay between 300,000 and 600,000 eggs, but the lack of parental care results in low survival rates.
Late sexual maturity: males mature at around 7 years, females at 9–10 years, making populations especially vulnerable to overfishing and environmental change.

Relationship with its environment

Plays a vital ecological role as a plankton filter feeder, helping maintain balance within large aquatic systems.
Populations depend on the natural state of river systems and are highly sensitive to hydrological alterations, water pollution and overexploitation.

Diet

In the wild

Plankton, including:

Algae (phytoplankton)
Microscopic crustaceans (zooplankton)

Under human care

Fed with nutrient-rich plankton-based diets, although maintaining this species is challenging due to its large size and filter-feeding needs.

Conservation status

The paddlefish (Polyodon spathula) is listed as Vulnerable on the IUCN Red List.

Populations have declined significantly due to  overfishing, habitat alteration  from human construction, and river pollution .

Protecting its natural environment — especially through the restoration of migratory routes and the improvement of water quality — is essential for the species’ long-term survival.

Main threats

Overfishing  for meat and roe.
Habitat fragmentation and degradation of river systems.
Water pollution and sedimentation.
Interruption of migratory pathways.