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Scaphirhynchus albus:   (click for more)

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FAO Names
En - Pallid sturgeon, Fr - , Sp - .
3Alpha Code: PHS     Taxonomic Code: 1170100402
Scientific Name with Original Description
Parascaphirhynchus albus  Forbes and Richardson, 1905: 37-44, Pls. 4-7. Bull. Illinois State Lab. Nat. Hist. v. 7 (art. 4) :38, Pls.4, 5(1), 6(1), 7(1). Mississippi River at or near Grafton, Illinois, USA.
Diagnostic Features
Spiracle absent. Snout flat, elongated and pointed. Caudal peduncle depressed, long, and completely armored. Mouth small, transverse. Lower lip continuous, with 4 lobes. Branchiostegal connection narrow. With spines at the snout tip and in the preorbital region. Eye very small. Inner barbels positioned anterior to outer barbels. Inner barbels shorter than outer ones. Barbels with accesory fringe.  14-18 (common 15-16) dorsal scutes. 40-48 (43-45) lateral scutes. 9-13 (11) ventral scutes. There are 9 scutes posterior to dorsal fin, 7-8 scutes posterior to anal fin, and 4-5 scutes between anus and anal fin. Most of the belly is naked at all ages, though large specimens may have small scattered scutes laterally, near the pelvic fins, or in the breast.  Very ligth, the upper parts bluish gray in life, the lower parts of the sides and belly shading from very ligth gray to almost milky white (mostly from Mayden & Kuhajda, 1996). 
Geographical Distribution
Endemic to Mississippi River Basin but naturally limited to the Missouri and lower Mississippi river drainages. Historic range includes Atchafalaya River, lower Mississippi River upstream to confluence with Missouri River, and Missouri River (Mayden & Kuhajda, 1997).
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Habitat and Biology
Inhabits the main channels of the rivers, along sandbars at the inside of river bends and behind wing dikes with deeply scoured trenches, usually in areas with swift current (Carlson et al., 1985).Prefer turbid water conditions that historically characterized the Missouri and lower Mississippi rivers. The abundance of this rare species has declined markedly following channelization and dam construction in these rivers.  The composition by frequency and volume of food categories is dominated by fishes and by aquatic insects, mainly Trichoptera, followed by Ephemeroptera, Odonata and Diptera (Carlson et al. 1997). The diet of adults is dominated by fishes (Cyprinidae). The habitat alterations have also impacted the naturally turbid characteristics of the Missouri and lower Mississippi rivers to the extent that, forage species of the pallid sturgeons are declining, being replaced with aquatic species adapted to these clear, lentic environments.
Males mature at 5-9 years, with 2 or 3 year intervals between spawning. The maturation of females is estimated to occur by 9 to 12 or 15 to 20 years of age, with 3 to 10 year intervals between spawning (Keenlyne & Jenkins, 1993). Pallid sturgeon has been observed with mature gametes coinciding with Spring high river flow levels. Spawning probably occur between Abril to mid-June and the spawning habitat is unknown. Like sholvenose sturgeon, eggs of pallid sturgeon probably are adhesive and require current for proper development.  Males reach 39 years, while females may live 41 years.
Size
Maximum size: 168 cm TL; weight: up to 45 Kg.
Interest to Fisheries
Species rare, listed as endangered by the U.S. Fish and Wildlife Service (Mayden & Kuhajda, 1997).
Local Names
UNITED KINGDOM : Pallid Sturgeon .
USA : Pallid Sturgeon .
Remarks
According to Mayden & Kuhajda (1997), there is no empirical evidence to support that the pallid and sholvenose sturgeon are the same species, or different ones in which the hybridization in the wild is common, as supported by some previous authors.
Bibliography
Bailey, R.M & F.B. Cross - 1954. River sturgeons of the American genus Scaphirhynchus: characters, distribution and synonymy. Pap. Michigan Acad.Sci., Arts and Letters .  39: 169-208..
Birstein, V.J. - 1993. Sturgeons and paddlefishes: threatened fishes in need of conservation. Conserv. Biol. .  7:773-787..
Birstein, V.J., Bemis, W.E & J.R. Waldman - 1997. The threatened status of acipenseriform species: a summary. Environm. Biol. Fish. .  48:427-435..
Carlson, D.M., W.L Phliegger, L. Trial & P.S. Haverland - 1985. Distribution, biology, and hybridization of Scaphirhynchus albus and S. platorynchus in the Missouri and Mississippi rivers. Environ. Biol. Fish. .  14: 51-59..
Keenlyne, K.D, E.M. Grossman & L.G. Jenkins - 1992. Fecundity of the pallid sturgeon. Trans. Am. Fish. Soc. .  121(1):1391-140 ..
Keenlyne, K.D & L.G. Jenkins - 1993. Age at sexual maturity of the pallid sturgeon. Trans. Am. Fish. Soc. .  122(3):393-396..
Keenlyne, K.D & S.J. Maxwell - 1993. Length conversions and length-weight relations for pallid sturgeon N. Am. J. Fish. Manage. .  13:395-397..
Mayden, R.L. & B.R. Kuhajda - 1996. Systematics, taxonomy, and conservation status of the endangered Alabama sturgeon, Scaphirhynchus suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae). Copeia .  1996(2): 241-273..
Mayden, R.L. & B.R. Kuhajda - 1997. Threatened fishes of the world: Scaphirhynchus suttkusi Williams & Clemmer, 1991 (Acipenseridae). Environ. Biol. Fish. .  48: 418-419..
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..
Williams, J.D & G.H. Clemmer - 1991. Scaphirhynchus suttkusi , a new sturgeon from the Mobile Basin of Alabama and Mississippi. Bull. Alabama Mus. Nat. Hist. .  10:17-31..
 
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