Pallid Sturgeon

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).

Maximum size: 168 cm TL; weight: up to 45 Kg.

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.

Species rare, listed as endangered by the U.S. Fish and Wildlife Service (Mayden & Kuhajda, 1997).