Dedicated to the Conservation of Southeastern Fishes
Paddlefish Making Comeback In Area Rivers
October 9, 2005
Lurking in the muddy depths of the Ohio River, bottom-dwelling ogres have been reported from Aliquippa to Weirton. The shark-like bottom-dwelling beasts of the backwaters have been estimated by worried residents to be as much as 5 feet long and weigh 150 pounds. Their yawning mouths and paddle-like beaks have been seen on full moon nights as they glide through the murky waters. However, the creatures are apparently docile, and boaters, anglers and swimmers need not worry about an attack by the giants of the deep.
Paul G. Wiegman
Well, I guess that could be a headline someday. Especially if an unsuspecting boater or angler came across what is the most unusual fish to ply our local rivers. That oddity, what someone might call the Ogre of the Ohio, is the paddlefish or spoonbill (Polyodon spathula).
Paddlefish are relatives of sturgeons and are known from fossil records that date back millions of years. These large, freshwater fish were once common throughout the Mississippi watershed from the Gulf of Mexico to Minnesota. Paddlefish were found in the large rivers of western Pennsylvania.
Deterioration in water quality, changes in the structure and flow of local waterways, and overharvest led to the extirpation (no longer present in Pennsylvania) of this odd species. Today, as the problems of the past have been reversed by conservation efforts, the water quality of area rivers has improved enough for paddlefish to again glide the deep pools and sluggish backwaters.
To jump start the return, the Pennsylvania Fish & Boat Commission reintroduced young paddlefish into the Ohio and Allegheny Rivers. The goal of the project is to re-establish a stable breeding population and thus add one more species to the aquatic diversity. The results of the effort will take time to judge because the species is long-lived and takes years to grow from young to breeding adults.
Recent net surveys are finding some sizable specimens of these oddities. Adults can indeed be monsters. A fully grown paddlefish is nearly 5 feet long and will weigh up to 150 pounds by age 17. They are believed to live for more than 50 years.
The common name of paddlefish or spoonbill comes from its long, flattened snout. The snout (technically called a rostrum) extends forward from the head, adding to the already long body. The rostrum is flattened top to bottom like a paddle. It was once thought that the species used the paddle to stir up the bottom mud or aquatic vegetation to shake loose small worms and insect larvae for food.
More recent studies of the rostrum and feeding habits have shown that the spoon shaped snout is an electrosensitive receptor that is used to locate concentrations of tiny aquatic plants and animals. These microscopic organisms are plentiful in healthy river water. When a paddlefish finds these microscopic organisms with its snout, it opens the gaping mouth and allows water to flow through rows of gill rakers just inside the jaw. As the water flows through these living filters, algae and tiny animals are sieved out and become food for the paddlefish.
This is the same feeding strategy used by some whales plying the open ocean. It's fascinating that the largest of marine species live on the smallest. The same is true for the paddlefish. It is one of the largest of our native fishes and it feeds on the smallest organisms found in the water.
Paddlefish mouths are large for the relatively thin sleek body, and the mouths have no teeth, again because they are filter feeders. The body of paddlefish is soft with a smooth, scaleless skin. Beneath, the skeleton is soft and pliable. The fish has no bones but a skeleton made of cartilage. This plastic-like material, half way between skin and bone, is a feature paddlefish share with sharks. In addition, their body is blue-gray on the upper surface and lighter below, and has a "Y"-shaped tail, both shark-like features. Nonetheless, paddlefish are not related to marine sharks, but are in a group of fishes all to themselves.
In the spring, when rivers are high from winter melt water, female paddlefish scatter sticky eggs over shallow, gravelly river bottoms. The young hatch and are on their own as soon as they are born. They are carried downstream into deeper water where they grow. That means that although local rivers are divided into large navigation pools separated by dams, if the species does take hold it will move into waterways where paddlefish were not originally stocked with young. The need of breeding females for shallow gravel bars points up the conservation need for local rivers to develop natural shallows for this and many other species.
Paddlefish aren't often seen by anglers. They are filter feeders and don't go after worms or lures. The breeding season is the most likely time to see paddlefish. As the females glide over shallow beds of gravel, they occasionally breach the surface and their long beaks can be seen.
At other times of the year, quietly drifting the backwaters of the Emsworth Dam in a kayak, canoe or small boat with the motor off, you might be fortunate to get a glimpse of an adult paddlefish slowly swimming near the surface with its huge mouth agape. If you do get to see one of these odd native fishes you're not facing a monster of the deep but rather are fortunate to have spotted one of the oddest fish in area rivers.