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Paddlefishes Temporal range: Late Cretaceous–Recent PreꞒ Ꞓ O S D C P T J K Pg N
American Paddlefish, Polyodon spathula
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Acipenseriformes
Family:	Polyodontidae Bonaparte, 1838
Genera
Polyodon Psephurus

Paddlefish (family Polyodontidae) are primitive Chondrostean ray-finned fishes. The paddlefish can be distinguished by its large mouth and its elongated, spatula-like snout, called a rostrum, which is longer than the rest of the head. These fish are not closely related to sharks, which are in a different taxonomic class, but they do have some body parts that resemble those of sharks such as their skeletons, primarily composed of cartilage, and their deeply forked heterocercal tail fins. This type of fish's age is hard to determine but many scientists think that they live 50 years or more.

There are only two modern species of these fish: the Chinese paddlefish (Psephurus gladius) and the American paddlefish (Polyodon spathula). Both have declined greatly in abundance, and the Chinese species may now be extinct. In some areas, paddlefish are referred to as "Spoonbill", "Spoonies" or "Spoonbill Catfish". The American species is Missouri's State Aquatic Animal.

Classification

There are two currently or recently extant genera in this family and four (if not five) extinct genera: Polyodontidae

• Subfamily †Paleopsephurinae
  • Genus †Paleopsephurus MacAlpin, 1947
    • Species †Paleopsephurus wilsoni MacAlpin, 1947

      

• Subfamily Polyodontinae
  • Genus †Crossopholis Cope, 1883
    • Species †Crossopholis magnicaudatus Cope, 1883
  • Genus Polyodon Lacépède, 1797
    • Polyodon spathula Walbaum, 1792 American paddlefish
    • †Polyodon tuberculata Grande & Bemis, 1991
  • Genus Psephurus Günther, 1873
    • Psephurus gladius E. von Martens, 1862 Chinese paddlefish (Not recently verified extant, and perhaps now extinct)
• Subfamily †Protopsephurinae Grande & Bemis, 1996
  • Genus †Protopsephurus Lu, 1994
    • Species †Protopsephurus liui Lu, 1994

The Chinese paddlefish (Psephurus gladius) is (or was) known only from the Yangtze River in China. Nine-foot (3-meter) specimens weighing 300 kilograms (660 lb) have been recorded, and reports of 7 metres (23 ft) fish exist, although the existence of such large specimens is doubtful. They may now be extinct, with a recently completed three-year survey of the Yangtze finding no specimens.

The American paddlefish (Polyodon spathula) is currently known from the Mississippi River watershed in the United States, including slow-flowing waters of the Mississippi River itself, as well as various tributaries including the Missouri River, Ohio River, Yellowstone River, Wisconsin River, Des Moines River, and Arkansas River systems. These fish were also found historically in Lake Erie, in the Great Lakes, but in May 2000, the Canadian Species at Risk Act listed the paddlefish as being extirpated in Canada.

The American paddlefish is one of the largest freshwater fish in North America. They commonly reach 5 feet (1.5 m) or more in length and can weigh more than 60 pounds (27 kg). The largest American paddlefish on record, weighing 144 pounds (65 kg), was caught by Clinton Boldridge in the Atchison Watershed in Kansas. The largest unofficial record was 206 pounds from Lake Cumberland in Kentucky; postcards from the 1960s show a photo of this huge fish.

Fossils of other kinds of paddlefish have been found. One such species is Crossopholis magnicaudatus, from the Eocene-age Green River Shale deposit in Wyoming.

Physical characteristics

Early investigators once thought that paddlefishes used their snouts to dig vegetation from the bottom of lakes and rivers. In fact, they feed by filtering out zooplankton from the water, using filaments on their gill arches called gill rakers, and in this respect appear similar to the basking shark.

As in many of the distantly related shark class, the paddlefish's rostrum contains receptors that can detect weak electrical fields, suggesting that they use their rostrum as an antenna to detect zooplankton. Even though the rostrum seems to help the fish feed, fish with severely damaged or missing rostrums are able to feed and appear to be just as healthy as other fish with them intact.

The rostrum also helps the fish to feed by acting as a stabilizer. As the fish moves through the water with its mouth open, the rostrum creates lift, much like a wing of an airplane. This helps the fish by keeping its head in a steady position and helps it keep from diving to the bottom.

Paddlefish lay their eggs in midstream over bare rocks or gravel. The eggs are adhesive and stick to the rocky substrate. The young are swept downstream after hatching and grow to adulthood in deep freshwater pools.

Status

Paddlefish were at one time very abundant in most central U.S. river systems, but populations have declined greatly due to overharvesting, sedimentation, and river modification. One of the major reasons for declining paddlefish numbers are the dams constructed on many major U.S. river systems. Paddlefish avoid fish ladders because of the metal rebar used in construction, which disrupts their electro-magnetic sense organs. The dams block paddlefish migration routes that are very important to the fish for spawning.

One other reason for the decreased numbers of paddlefish is overfishing. Pennsylvania Fish and Boat Commissioners are reintroducing the species to historical habitats in the Ohio and Allegheny rivers in an effort to establish a secure breeding population once again. Reintroduction efforts may take many years, since paddlefish mature slowly, lengthening the time required to establish a breeding population. Oklahoma has drastically reduced sportfish harvest of paddlefish to one per person per day to help sustain populations. Paddlefish are a protected species in Wisconsin, where they occur only in the Wisconsin River south of the Prairie Du Sac hydroelectric dam.

Caviar harvest

During the last century, paddlefish and sturgeon have been commercially exploited for their eggs (roe), called caviar. Paddlefish and sturgeon are two of the most important fish for freshwater caviar. Paddlefish take many years before they are able to spawn. A female may take nine to ten years, when they are about 42 inches long, and males seven-years-old and 40 inches long are able to spawn. The female releases adhesive eggs randomly over the water bottom and abandons them. They are capable of producing over a half million eggs a year, but they may not spawn every year.

The Oklahoma Fish and Game Department set up Paddlefish Survey stations in various highly fished areas in the state. The Fish and Game biologists record length and weight measurements, and cut a portion of the lower jaw to determine age. To encourage participation in past surveys the Fish and Game Department has offered fish cleaning and preparation services, returning the cleaned fish in heat-sealed packaging, and has offered key tag souvenirs. The Fish and Game department keeps the eggs (roe) for licensed resale, with the proceeds keep the study funded without expense to the public.

Current threats

Paddlefish are targeted by poachers for their valuable eggs, and are protected by law over a large part of their range. Habitat destruction is also causing their numbers to decrease more rapidly. Paddlefish need free-flowing rivers that have shallow pools with sandy, rocky bottoms for their spawning. Water temperature is also important for spawning. Modification of rivers by the construction of dams, dredging, and water removal for agricultural use reduces paddlefish spawning grounds.

Free-flowing lakes with reservoirs can also provide paddlefish breeding habitat. One such area is the Missouri River-Lake Sakakawea system in North Dakota. This area is capable of producing good paddlefish numbers because it is a free-flowing system with many good areas for paddlefish to spawn.

Fishing for paddlefish

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In most of its range the paddlefish is a protected species, and fishing for paddlefish is a felony in many areas. Any paddlefish caught accidentally should be released unharmed as quickly as possible.

Because paddlefish are filter feeders, they do not take conventional lures. This factor, and their generally low abundance, makes them an unattractive target for many sport fishermen. Also, because they will not take lures, the methods employed to catch paddlefish provide little possibility of releasing the fish in good health and usually result in the death of the fish. In an increasingly conservation-minded sportfishing community, using methods that result in the death of a fish which is in chronic decline nationally is considered unethical. Most anglers instead use conventional methods to catch and release more abundant species such as bass, walleye, pike, trout, perch, crappie, whitefish, suckers, salmon, and catfish.

However, a few states still allow sport fishing for paddlefish. Where legal, taking paddlefish is done with a bow and arrow, a spear, or by snagging (deliberately foul-hooking the fish in the fins or tail). Snagging is the usual method.

Poachers also use these methods to target paddlefish in areas where paddlefish fishing is not legal. Snagging paddlefish is prohibited in most states. Suspect paddlefish fishing activity can be reported to fish and wildlife officers who will verify legality. Some jurisdictions pay a financial reward to citizens whose report leads to prosecution of a poacher. One example is the Iowa DNR, and their Turn In Poachers (TIP) Program which was started in August 1985. The private TIP organization was established by concerned sportsmen and women under the guidance of the Iowa Department of Natural Resources Law Enforcement Bureau. Both groups recognized the need for an added dimension to fish and game law enforcement in the State of Iowa to aid in the fight against poaching.

References

1. Froese, Rainer; Pauly, Daniel (eds.). "Family Polyodontidae". FishBase. January 2009 version.
2. Revkin, Andrew C. (2009-09-30). "For Chinese Paddlefish, a Long Goodbye". The New York Times. Retrieved 2010-05-20.
3. ^ Wiley, Edward G. (1998). Paxton, J.R. & Eschmeyer, W.N. (ed.). Encyclopedia of Fishes. San Diego: Academic Press. pp. 77–78. ISBN 0-12-547665-5.{{cite book}}: CS1 maint: multiple names: editors list (link)
4. Missoulian.com

• Grandfishingreport.com on spoonbills

External links

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Paddlefish" – news · newspapers · books · scholar · JSTOR (September 2011) (Learn how and when to remove this message)

• The Chinese Paddlefish Website - containing many photographs of Psepherus.
• ARKive - images and movies of the paddlefish (Polyodon spathula)
• FishBase entry for Polyodontidae
• USGS UMESC Paddlefish Study
• Sites.state.pa.us
• Fisheries.org
• DNR.state.oh.us
• Stochastic synchronization of electroreceptors in the paddlefish
• Outdoorlife.com
• Earthwave Society

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• Polyodontidae