Fish

Paddlefish

Polyodon spathula · also called American paddlefish, spoonbill

Vulnerable ↓ filter feeder Rivers & wetlands

A paddlefish looks like a fish designed by committee: a shark’s cartilage skeleton, a shape built for endless cruising, and a long flat snout that does not dig or strike but simply listens for the electrical hum of drifting plankton. Its Asian relative was even larger — until dams and decades of overfishing on the Yangtze River ended in the species being declared extinct in 2022.

Overview

The American paddlefish, Polyodon spathula, is an ancient, shark-shaped filter feeder of the Mississippi River basin, reaching around 2 metres. It belongs to Acipenseriformes, the same ancient order as the sturgeons, with a fossil record over 300 million years old, and as an adult it has no functional teeth, relying entirely on straining zooplankton through comb-like gill rakers.

A snout that senses electricity

The long, flat rostrum is covered in electroreceptors that detect the faint electrical fields given off by swarming plankton, letting the fish locate dense prey patches in murky or dark water without needing to see them — then swim straight in with its mouth open.

A relative already lost

The Chinese paddlefish, once the largest freshwater fish in Asia at 3 metres or more, was declared extinct in 2022 after Yangtze River dams blocked its spawning migration and decades of overfishing removed breeding adults faster than the slow-maturing species could replace them — one of the starkest freshwater fish extinctions of modern times.

Status

Vulnerable — the American paddlefish has declined significantly from dams, channelisation, and historic overfishing for its roe, now farmed as a caviar substitute that has eased some pressure on wild sturgeon.

Paddlefish: common questions

How does a paddlefish use its long snout?

The paddle-shaped snout is not used for digging, probing, or striking prey the way it might first appear, but as a highly sensitive electrical detector. Its surface is covered in an enormous number of tiny pores connected to electroreceptor cells that pick up the weak electrical signals given off by the muscles of tiny swimming animals such as zooplankton, letting the fish sense where a dense swarm of prey is located, even in dark or turbid water, well before it could see or otherwise detect it, and then swim directly into that patch with its mouth open to filter feed.

Is a paddlefish related to a shark?

Not closely, despite a similar overall shape and a skeleton made mostly of cartilage rather than bone. A paddlefish is a bony fish belonging to Acipenseriformes, the ancient order that also includes the sturgeons, while sharks belong to an entirely separate and much older lineage of cartilaginous fish. The superficial similarities in body shape and skeletal material arose independently in the two groups through convergent evolution, both having found that a cartilage-heavy, streamlined build suits a life of steady cruising through open water.

What happened to the Chinese paddlefish?

The Chinese paddlefish, once the largest freshwater fish in Asia, declined drastically over the second half of the 20th century as a result of intense overfishing that removed breeding adults faster than the slow-growing, slow-maturing species could replace them, combined with the construction of major dams on the Yangtze River that blocked its long upstream spawning migration and fragmented its habitat. Surveys failed to find any surviving individuals for years despite extensive searching, and in 2022 the species was formally assessed and declared extinct, one of the largest and most significant freshwater fish extinctions documented in recent times.

Why are paddlefish farmed for their eggs?

Paddlefish roe has a flavour and texture reasonably comparable to traditional sturgeon caviar, and because paddlefish grow somewhat faster and are generally easier to farm than most sturgeon species, aquaculture operations in several countries raise them specifically to harvest and sell their eggs as a caviar substitute or blend. This provides a commercially viable alternative source of roe that reduces some of the market pressure driving illegal or unsustainable fishing of wild sturgeon, whose populations have collapsed across much of their range from a combination of overfishing for caviar, damming, and pollution.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Polyodon spathula
Diet: A filter feeder that swims forward with its huge mouth open, straining zooplankton, tiny crustaceans, and other minute animals from the water through long, comb-like gill rakers, needing no visual targeting at all to locate concentrated patches of prey
A snout that senses electricity: The long, flat, paddle-shaped snout, called a rostrum, is densely covered with tens of thousands of tiny electroreceptor organs that detect the faint electrical fields produced by the muscle contractions of swarming zooplankton, letting the fish find and swim directly into dense prey patches even in murky water or darkness
An ancient, nearly toothless lineage: Paddlefish belong to Acipenseriformes, the same ancient order as the sturgeons, a group with a fossil record stretching back over 300 million years, and the adult has no functional teeth, relying entirely on filtering rather than biting or grasping prey
One of the largest North American freshwater fish: The American paddlefish can grow to around 2 metres long and over 45 kilograms, with a skeleton made mostly of cartilage rather than bone, similar to a shark, though the two are not closely related and arrived at a broadly similar body plan independently
A relative now extinct: The Chinese paddlefish, once the largest freshwater fish in Asia at up to 3 metres or more, was formally declared extinct in 2022 after decades of overfishing and the damming of the Yangtze River blocked its spawning migration, making it one of the most significant documented freshwater fish extinctions of the modern era
Farmed for roe as a caviar substitute: American paddlefish are farmed in several countries, and their eggs are harvested and sold as a caviar substitute, providing an alternative source of roe that has helped reduce some of the fishing pressure on wild and farmed sturgeon, whose own populations are heavily depleted
A slow-growing, long-lived fish: Paddlefish grow slowly, do not reach breeding maturity for roughly 7 to 10 years in females, and can live several decades, which makes wild populations slow to recover from overfishing, habitat loss, or the river damming that blocks the long upstream migrations they need to spawn successfully
Range: The Mississippi River basin and its major tributaries in the central United States, in large, slow-flowing rivers, backwaters, and connected lakes and reservoirs, historically also including some Great Lakes tributaries, requiring long stretches of connected river and specific gravel bars for spawning, with the related Chinese paddlefish formerly found in the Yangtze River system before its extinction.
Conservation status: Vulnerable ↓ ≈ The American paddlefish is assessed as Vulnerable, having declined significantly across much of its range in the Mississippi River basin due to dam construction that blocks spawning migrations and floods the gravel bars it needs to lay eggs, river channelisation, pollution, and historic overfishing for its roe. Some populations are now maintained partly through stocking programmes. Its close relative the Chinese paddlefish of the Yangtze River suffered a far worse fate, declining from a healthy population to extinction over the course of the 20th century as dams blocked its migration and overfishing removed breeding adults, and it was formally declared extinct in 2022, one of the starkest recent examples of a large freshwater fish being lost entirely in the wild