|Family overview: Paddlefish are known from fossil records to be millions of years old. They are related to sturgeons. In North America, and Pennsylvania, there is only one paddlefish species, Polyodon spathula, which is called the “paddlefish.” Its closest living relative is a species that lives in China.
Paddlefish are widely distributed throughout the Mississippi River watershed. In some states, the paddlefish is a threatened species because of the loss and degradation of its large-river habitat. It prefers big, deep pools with sluggish current. In Pennsylvania, paddlefish were once reported to be in Lake Erie, the Allegheny River and Clarion River, but were believed to be extirpated (no longer present in the state). Paddlefish were recently reintroduced by the Pennsylvania Fish & Boat Commission into their historical habitats in the Ohio and Allegheny rivers, in an effort to reestablish a secure, breeding population. Reintroduction efforts for species that take many years to mature require many years to determine the success of such efforts.
The genus name “Polyodon” means “many teeth,” referring to the fish’s many gill rakers. The species name “spathula,” like “spatula,” refers to a blade or paddle.
Identification: The paddlefish’s most distinctive feature is its snout, or rostrum. This “paddle” is longer than the rest of the head and flattened on top and bottom, like a paddle. The snout is thought to be an organ of touch. It may also act as a stabilizer, keeping the fish swimming in a horizontal position when its jaw is extended downward during filter-feeding. Paddlefish have many long gill rakers that let them strain tiny food organisms from the water. Like the sturgeon, the paddlefish tail’s upper lobe is longer than its lower lobe, but it has no bony scales or plates on its body. The skeleton is mostly cartilage. The paddlefish’s gill cover extends backward in a long, flat point. The body color is generally medium to pale blue-gray. Young paddlefish don’t have the adult’s paddle-shaped snout. Young paddlefish also have teeth, which the adults lack.
A paddlefish swims through the water swinging its open mouth from side to side while filter-feeding for zooplankton and other small aquatic insects.
Life history: Paddlefish are travelers. They range long distances in the spring in the large rivers where they live to spawn on submerged gravel bars in swift current. During the spawning season, they may be seen breaking the water’s surface. Paddlefish release their adhesive eggs randomly over the bottom, and abandon them. Large females may produce over one-half million eggs a year, but may not spawn every year. Like sturgeons, paddlefish take a long time to become sexually mature and capable of spawning. Paddlefish males are ready at seven years and about 40 inches long. Females take nine or 10 years, and are about 42 inches long when they first spawn. Paddlefish grow rapidly and may reach five feet long when they are 17 years old. They are believed to live for 20 years or more. The world hook and line record is over 140 pounds.
Unlike its sturgeon relatives, the paddlefish does not feed on the bottom. Instead, it swims near the surface or in shallow water, feeding on minute plant and animal organisms, and on small aquatic insects, like mayflies.