by Dudley Parr, illustrations by Ted Walke
Cruising in the murky waters of western Pennsylvania's big rivers is one of the oldest and largest freshwater fishes of North America. With its long, paddle-shaped snout, grayish-colored body, and large tail, this creature looks like a cross between a swordfish and a shark. But this gentle giant has no teeth and feeds only on zooplankton and aquatic insect larvae that it filters from the water. In the South, this living relic is called the spoonbill. Known as Polyodon spatula to the biologist, this creature is the paddlefish.
Paddlefish can live to be 30 or more years old. As one of the largest freshwater fishes, paddlefish may grow to six feet or more in length and weigh more than 100 pounds. Paddlefish vary in color from black to bluish-gray, which fades to white on the sides and belly. The skin is smooth and nearly scaleless. They have small eyes near the base of the rostrum (snout), providing only poor vision. The large tail, with the top portion bigger than the bottom portion, gives them a shark-like appearance. The mouth is large and toothless, but combined with the closely set gill rakers, the mouth makes an effective seine to filter the zooplankton on which it feeds. The elongated opercula (gill covers) allow for expansion of the gill openings and mouth while filter-feeding. Another characteristic that marks the paddlefish as an ancient fish is its skeleton. The skeleton is made entirely of cartilage except for the jaw, which is bone.
photo at right-Craig Bihrle
The paddle-shaped rostrum, as the snout is properly called, is approximately one-third the fish's total length. Although paddlefish fry are not born with the bill for which they are named, the rostrum starts growing shortly after birth. Biologists are not sure about the rostrum's function. For years, many people believed wrongly that it was used to dig in the mud. The rostrum has many sensory and electro receptors that may aid in detecting concentrations of zooplankton. The rostrum may help balance the fish while swimming with its large mouth open. However, paddlefish that have lost part or all of the rostrum seem to suffer no ill effect and so cast doubt on its true use.
view from above
view from below
Paddlefish are found only in North America. There is only one other species in the Polyodon family, which is found in China. Paddlefish are found in the large, free-flowing rivers of the Mississippi Basin. They prefer backwaters, ox bow lakes, and areas where currents are reduced. Big islands, bridge pilings, shoals, and sand bars provide such sheltered areas. Examples of good paddlefish habitat in the Three Rivers area are the confluence of the Beaver and Ohio rivers, around Neville Island in the Ohio, and the islands and bridges at the upper end of Pool 2 on the Allegheny. Although lakes and reservoirs can provide good feeding areas for paddlefish, the dams that create them have inundated suitable spawning habitat and are barricades to paddlefish during spawning migrations.
Compared to most fish, paddlefish mature late in life. Males reach sexual maturity at seven to nine years of age, or after about one-fourth of their expected life span. Females mature at 10 to 12 years of age, or after about one-third of their expected life span. Although males may spawn every year, females require two or more years to produce up to 10 to 12 pounds of eggs. The eggs are valuable as a source of high-quality caviar. photo at right-Craig Bihrle
Until 1960, little was known about paddlefish spawning behavior or habitat requirements. Environmental conditions have to be just right for spawning to occur. Paddlefish need clean gravel bars with good current flows. The water temperature must be near 60 degrees, the water flows must be high and rising, and all of this needs to happen in the spring. A sudden water level rise of six feet has been documented to trigger spawning activity. These environmental factors don't coincide every year. Thus, paddlefish may not spawn every year.
When spawning does occur, it is a simple act. A large female, accompanied by a couple of usually smaller males, swims over the selected gravel bar. Both sexes release their respective eggs and milt. Fertilization occurs in the water and the eggs become sticky. The sticky eggs adhere to the gravel substrate so that they don't wash away. The high water flow keeps the eggs well-oxygenated and keeps debris and silt from covering them. In about a week, the eggs hatch and the larval paddlefish are swept downstream to quieter nursery waters. In a few days, the yolk sac is absorbed and the young fish feed first on small insects. Then they begin their lifelong pursuit of zooplankton.
Young paddlefish are not good swimmers. Their only defense from being eaten is to grow large fast. It is amazing that the paddlefish can attain its great size feeding only on creatures the size of the period at the end of this sentence. This means that volume of food is the key to paddlefish survival and growth.
In some states, paddlefish populations are healthy enough to support active sport fisheries. Because paddlefish feed on microscopic organisms, traditional fishing techniques are not successful. Most anglers catch paddlefish by snagging. In recent years, a few paddlefish have been inadvertently "foul-hooked" and released by Pennsylvania anglers in the Ohio and Allegheny rivers. The paddlefish season is permanently closed in Pennsylvania. The flesh is compared to swordfish in flavor and the roe (eggs) is sought for caviar. A recent estimate of the value of a pound of processed paddlefish eggs was $360.
Reintroducing the paddlefish
Paddlefish have been swimming in the large rivers of the Mississippi Basin since before the dinosaurs. Until the early 1900s, their range included the Ohio, Allegheny, Clarion, and Kiskiminetas rivers in Pennsylvania. Paddlefish stocks declined throughout much of their range because of the channelization of rivers, building dams, and degradation of water quality from pollution. In Pennsylvania, paddlefish are currently classed as extirpated. The last documentation of paddlefish in Pennsylvania waters was in 1919. Today, the only paddlefish in Commonwealth waters are those put there by the Fish and Boat Commission.
Since 1991, the Commission has been stocking fingerling paddlefish in the Ohio and Allegheny rivers as part of its Paddlefish Restoration Plan. In the late 1980s, a private citizen from the Pittsburgh area, Mike Koryak, first suggested reintroducing extirpated, native fishes. As indicated by the return of many other fish species, the water quality in the Three Rivers area has greatly improved during the last 35 years. Given the improved water quality, the abundance of zooplankton, and presence of appropriate habitat, it seems likely that the paddlefish could once again take up residence in Pennsylvania.
After careful study, a plan was developed with the objective of restoring a paddlefish population to the Ohio and Allegheny rivers. The female paddlefish takes 10 years to reach reproductive age, so the project will span at least a decade.
Each May, James E. Harvey, Manager of the Linesville Fish Culture Station, and his staff receive paddlefish fry from the U.S. Fish and Wildlife Service in South Dakota. Using paddlefish hatchery methods developed in Missouri, South Dakota, and Texas, they raise the young paddlefish, which grow rapidly at approximately one inch per week.
In late July, Rick Lorson, Commission Area 8 Fisheries Manager, and his crew tag each paddlefish with a tiny coded wire. The coded wire, which indicates where and when the fish was hatched and stocked, is inserted into the tip of the rostrum. If the fish is later collected, a tag detector will indicate the presence of the wire tag. The tag can then be recovered without killing the fish, and the origin of the fish can be determined. Along with measurements of length and weight, knowing the age and origin is important for evaluating the paddlefish's comeback. In future years, surveys will be conducted to assess the paddlefish population and the success of the program.
Photo at right, Commission personnel tag each paddlefish with a tiny coded wire. The coded wire indicates where and when the fish was hatched and stocked. It is inserted into the tip of the rostrum. If the fish is later collected, a tag detector will indicate the presence of the wire tag. The tag can then be recovered without killing the fish, and the origin of the fish can be determined.top. photo-Dudley Parr
About 10 weeks after the eggs are received, the paddlefish have grown to about 10 inches and are ready for stocking. This usually occurs in early August. With the help of the local waterways conservation officers, an average of 10,000 young paddlefish are stocked each year.
So far, no surveys that target paddlefish have been conducted. The Commission is currently seeking a funding source for evaluation of the restoration efforts. However, the Fish & Boat Commission does have some data on paddlefish in Pennsylvania. Since 1992 there have been a total of 12 reported paddlefish sightings. With each successive year, the average size of the fish sighted has gone up. Six paddlefish were inadvertently snagged by anglers and released. (Remember, in Pennsylvania, there is no open season on paddlefish.) Three of those paddlefish were captured during other river study projects. Another two paddlefish were found dead along the shore, and one was spotted swimming below a dam.
Although the sample is too small to give an accurate assessment, it tells us that there are paddlefish in Pennsylvania and they seem to be getting bigger.
The paddlefish predates the dinosaurs and is little changed from its ancient ancestors. This fact makes paddlefish sensitive to environmental degradation. The lock and dam system, dredging, and deteriorated water quality are all manmade conditions that led to the paddlefish's demise in Pennsylvania. We have cleaned up our waters enough for paddlefish to survive. For as much as we take from our rivers, it is important for us to give something back. It is right for us to return this great fish to its place in our waters. With diligent monitoring of water pollution and persistent cleanup efforts, we can continue to improve water quality for ourselves as well as for the paddlefish. If the Paddlefish Plan proves successful in Pennsylvania, the sturgeon, and other extirpated large river species, will be considered for restoration.
The author thanks Commission Area 8 Fisheries Manager Rick Lorson for his help in preparing this article.
Paddlefish Polyodon spatula
1. Rostrum (bill) -The paddle-shaped bill, for which the fish is named, may aid in balance while feeding and in detecting concentrations of zooplankton.
2. Eyes-Small, weak eyesight.
3. Operculum (gill cover)-Elongated, swept-back shape helps water pass through efficiently while filter-feeding.
4. Heterocercal tail-Spinal column curves up into the upper part of the tail. Triangular dorsal fin.
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January/February 1999 PA Angler & Boater
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