Fish
American Paddlefish
Polyodon spathula · also called American paddlefish, Mississippi paddlefish, spoonbill, spoonbill catfish
The American paddlefish looks like a shark that swallowed a canoe paddle. It cruises the Mississippi’s murky rivers with its mouth hanging open, straining clouds of near-invisible plankton, and it navigates those swarms with an electrical sixth sense spread across a snout as long as a person’s arm.
Overview
American paddlefish live in the large, slow rivers, backwaters, and reservoirs of the Mississippi basin and Gulf drainages. They are filter feeders, eating almost nothing but zooplankton strained through comb-like gill rakers as they swim with the mouth agape. Adults are toothless, commonly 1.2–1.5 m, with the biggest past 2 m and 90 kg.
The electric paddle
The long flat rostrum is not a scoop — it is a sensory antenna covered in tens of thousands of electroreceptors that detect the tiny electrical fields of individual plankton, letting the fish find and hold position in a swarm where eyesight is useless.
Deep ancestry
Paddlefish are close cousins of sturgeons and have barely changed in over 120 million years, keeping a mostly cartilage skeleton, near-scaleless skin, and a shark-like tail. Only two species ever existed; the Chinese paddlefish was declared extinct in 2022 after the Yangtze was dammed.
Status
The American paddlefish is Vulnerable and declining, gone from the edges of its range. It needs free-flowing rivers with spring floods to spawn, which dams have removed, and it is sustained by hatchery stocking and harvest limits — while poaching for roe sold as caviar remains a pressure.
American Paddlefish: common questions
What is the paddle on a paddlefish for?
It is a sensory organ, not a tool for digging or scooping as people often assume. The long, flat rostrum is packed with tens of thousands of tiny electroreceptors (ampullary organs, similar to those of sharks) that sense the weak bioelectric fields given off by the swimming muscles and beating appendages of individual zooplankton. Because paddlefish live in turbid rivers where they cannot see their microscopic prey, this electrical sense lets them detect and home in on the dense clouds of water fleas and copepods they feed on, and to keep the fish oriented within a swarm as it feeds. The paddle also provides some hydrodynamic lift that helps counteract the drag of swimming with the mouth wide open.
How does a paddlefish eat?
By filter feeding, the same basic strategy as a baleen whale, a whale shark, or a basking shark, just at small scale. When it encounters a swarm of plankton, the paddlefish opens its enormous mouth and swims steadily forward so that water pours in and out over the gills. Long, closely spaced comb-like structures called gill rakers act as a sieve, trapping the zooplankton while letting the water pass through, and the fish periodically swallows the collected mass. Adult paddlefish have no teeth at all. Young paddlefish under about 25 cm still have some teeth and feed by picking individual prey items before switching to filter feeding as their gill rakers develop.
Is the paddlefish related to the shark?
No, despite the shark-like tail, the mostly cartilage skeleton, the smooth skin, and the electroreception, which all invite the comparison. The paddlefish is a ray-finned bony fish, in the same ancient group (Acipenseriformes) as the sturgeons, which are its closest living relatives. The similarities to sharks are a mix of shared primitive features that early bony fishes and sharks both had, and convergent evolution — the electroreceptive rostrum, for instance, solves the same problem sharks' electroreceptive snouts do, but evolved separately. Paddlefish and sturgeons split from other bony fishes very early, which is why they look so unlike a typical modern fish.
Why did the Chinese paddlefish go extinct, and is the American one at risk?
The Chinese paddlefish (Psephurus gladius) of the Yangtze, which grew to perhaps 3 metres or more, was declared extinct in 2022, with no confirmed sightings since 2003. Its collapse was driven by overfishing and, decisively, by the damming of the Yangtze — especially the Gezhouba Dam in 1981, which cut the fish off from its only known spawning grounds. The American paddlefish faces the same pressures on a less severe scale — it is listed as Vulnerable, it has disappeared from the edges of its range, and it depends on free-flowing rivers with gravel bars and spring floods to spawn, which dams and channelisation have removed across much of the Mississippi system. Where it survives, it is heavily supported by hatchery stocking, strict harvest rules, and, in some rivers, fish passage and flow management.