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Polyodon spathula:   (click for more)

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Synonyms
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  • Squalus spathula  Walbaum, 1792: 52.
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  • Polyodon folium  Bloch & Schneider, 1801:457.
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  • Spatularia reticulata  Shaw, 1804:362.
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  • Platirostra edentula  Lesueur, 1817:227.
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  • Acipenser lagenarius  Rafinesque, 1820:86.
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  • Proceros maculatus  Rafinesque, 1820:87.
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  • Platirostra spatula  Owen, 1853:83.
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  • Polyodon spathula  Jordan & Gilbert, 1883:83.
    FAO Names
    En - Mississippi paddlefish, Fr - Spatule d'Amérique, Sp - Espátula.
    3Alpha Code: PAM     Taxonomic Code: 1170200201
    Scientific Name with Original Description
    Squalus spathula  Walbaum, 1792:52. Artedi Piscium Pt.3. Mississippi River, Louisiana.
    Diagnostic Features
    Snout prolonged, expanded into a thin flat blade, somewhat flexible.  Spiracles present. Opercular skin produced behind into a long acute flap, nearly reaching to ventrals. No tongue. No barbels.  Jaws and palatines with many fine deciduous teeth.  Gill rakers long and in the hundreds. Gill rakers become fully functional when fish reach 225-250 mm eye-to-fork length (Rosen & Hales, 1981). Isthmus papillose in the young. Gill membranes considerably connected to one another, free from the isthmus.  Ventrals near the middle of the body. Dorsal well behind them. Anal mostly behind the dorsal and somewhat larger. Caudal fin heterocercal, the lower caudal lobe is well developed, so that the fin is nearly homocercal. D: 50-60; A:50-65; V:45; caudal fulcra:13-20.  Skin smooth, or nearly so, except rhombic plates on the sides of the bent portion of the tail.  Colour pale olivaceous (mostly from Jordan & Evermann, 1896) 
    Geographical Distribution
    Mississippi River system, particularly Missouri and their major tributaries. Although peripherical range has dwindled, paddlefish still occur over most of their historical range and are still found in 22 states of the USA (Graham, 1997).
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    Habitat and Biology
    The Mississippi paddlefish inhabits slow-flowing water of large rivers, usually in water deeper than 1.3 m, and with abundant zooplancton. Adult specimens typically swim through the water both day and night.Adult specimens typically swim with the nonprotrusible mouth open, strining zooplancton and aquatic insect larvae indiscriminately through the gill rakers. Adult paddle fish are indiscriminate filter feeder ingesting all material strained from the water colum by the gill rakers. Its stomachs contain the same organisms as the plankton but smaller forms (small cyclopoid, copepodits, nauplii, rotifers, etc. ) were almost entirely absent. Daphnia pulex, calanoids copepodits, Diaptomus siciloides was the most important food item by volume (Rosen & Hales, 1981). Juveniles, in which neither gill rakers nor the paddle are completely developed, pick individual zooplankters present, mainly insects (Rosen & Hales, 1981).
    The age at first maturity is 7 to 9 years for males and 10 to 12 years for females. The spawn only at 2- to 5-year intervals. Appropiate spawning areas are degradated by damming, which decreases water flow and leads to siltation. 
    Size
    Maximum size: 221 cm TL; maximum weight: 91 kg; maximum reported age: 30 years.
    Interest to Fisheries
    Arkansas and Tennessee report the largest commercial fisheries: 136.000-181.000 Kg and Tennessee 60.328 kg, respectively, in 1992. All states bordering the Missouri River now prohibit commercial fishing for paddlefish because harvest were small and size of fish was decreasing (Graham, 1997).
    Local Names
    DENMARK : Skestør .
    FINLAND : Lapasampi .
    FRANCE : Poisson spatule .
    GERMANY : Paddelfisch ,  Löffelstör .
    ITALY : Pesce spatola .
    NORWAY : Skjestør .
    POLAND : Wioslonos amerykanski .
    PORTUGAL : Peixe-espátula .
    RUSSIAN FED. : Veslonos .
    SPAIN : Pez espátula .
    SWEDEN : Skedstör .
    UNITED KINGDOM : Mississippi paddlefish .
    USA : Paddlefish .
    Bibliography
    Bemis, W.E, E.K. Findeis & L. Grande - 1997. An overview of Acipenseriformes Environ. Biol. Fish. .  48: 25-71..
    Birstein, V.J. - 1993. Sturgeons and paddlefishes: threatened fishes in need of conservation. Conserv. Biol. .  7: 773-787..
    Carlander, K.D - 1969. Handbook of freshwater fishery biology , volume 1. The Iowa State University Press, Ames. Iowa . 
    Dingerkus, G & W.M. Howell - 1976. Karyotypic analysis and evidence of tetraploidy in the North American paddlefish, Polyodon spathula. Science .  194(4267): 842-844..
    Graham, K. - 1997. Contemporary status of the North American paddlefish, Polyodon spathula. Environ. Biol. Fish. .  48: 279-289 ..
    Houser, A. - 1965. Growth of paddlefish in Fort Gibson Reservoir, Oklahoma. Trans. Am. Fish. Soc. .  94(1):91-93 ..
    Jordan, D.S & B.W. Evermann - 1896. The fishes of North and Middle America, a descriptive catalogue of the species of fish-like vertebrates found in the waters of North America, north of the isthmus of Panama. Bull. U.S.Natn. Mus. .  47, Part I: 1240 p ..
    Mero, S.W., D.W. Willis & G.J. Power - 1994. Walleye and sauger predation on paddlefish in Lake Sakakawea, North Dakota. N. Am. J. Fish. Manage. .  14(1):226-227..
    Nelson, J.S - 1994. Fishes of the world 2nd ed. John Wiley and Sons, Inc. N. York. .  523 p ..
    Page, L.M & B.M. Burr - 1991. A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. .  432. p.
    Reed, B.C.,, W.E. Kelso & D.A. Rutherford - 1992. Growth, fecundity, and mortality of paddlefish in Louisiana. Trans. Am. Fish. Soc. .  121(3):378-384..
    Rosen, R.A & D.E. Hales - 1981. Feeding of paddlefish, Polyodon spathula. Copeia. .  2: 441-455 ..
    Rosen, R.A., D.C. Hales & D.G. Unkenholz - 1982. Biology and exploitation of paddle fish in the Missouri River below Gavins Point Dam. Trans. Am. Fish. Soc. .  111(2):216-222..
     
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