8094

• UCREFRP Catalog Number: 8094
• Author: Dryer, M. P. and A. J. Sandvol.
• Title: Recovery Plan for the Pallid Sturgeon ‎(
• USFW Year: 1993.
• Copyright Material: NO

invertebrates (principally the immature stages of insects) composed .most of
the diet of shovelnose sturgeon, while pallid sturgeon and presumed hybrids.
consumed a greater proportion of fish (mostly cyprinids). Other researchers
also reported a higher incidence of fish in the diet of pallid sturgeon than
in the diet of shovelnose sturgeon (Cross 1967; Held 1969).
Most piscivorous Missouri River species eat large quantities of aquatic insect
larvae in early life and even as adults.. Shovelnose sturgeon were found to
consume large numbers of Hydropsyche spp. and Psychomyiidae (Tricopteran
larvae) (Modde and Schmulbach 1977).
gge and Growth: Little is known about age and growth of pallid sturgeeon. The
total length of pallid sturgeon was significantly greater than that of
shovelnose sturgeon in the lower Missouri and Mississippi Rivers for each age
group in which comparable data were available (Carlson et al. 1985). Fogle
(1963) estimated growth rates using cross sections of pectoral fin rays from
six pallid sturgeon from Lake Oahe in South Dakota. He estimated that growth
of these fish was relatively rapid during the first 4 years, but that growth
decreased to approximately 70 mm (4 in) per year between .ages 5 and 10.
Carlson and Pflieger (1981) presented data (n=8) from the Missouri and-
Mississippi Rivers in Missouri, which showed slightly slower growths than from
pallid sturgeon in South Dakota.
By interpreting cross. sections of pectoral fin rays, L, Jenkins (pers. comm.
1991) estimated that pallid sturgeon can-live more than 40 years.
Reasons for Decline
Habitat Loss: Destruction. and alteration of habitats by .human modification. of
the river system is believed to be the primary cause of declines in
reproduction, .growth, and survival of pallid sturgeon.. It is unlikely that
successfully reproducing populations of pallid sturgeon can be recovered
without restoring the habitat elements (morphology, hydrology, temperature
regime, cover, and sediment/organic matter transport)- of the Missouri and
Mississippi Rivers necessary for the species continued survival..
On the main stem of the Missouri River, approximately 36 percent of riverine
habitat within the pallid sturgeon's range was eliminated by constructipn of
six massive earthen dams between 1926 and 1952 and another 40 percent has been
channelized. The remaining 24 percent has been altered due to .changes in
water flows caused by dam operations.
These dams also are believed to have adversely affected pallid sturgeon by
blocking migration routes and by causing inundation of spawning and nursery
areas.
Channelization of the Missouri and Mississippi Rivers began at the turd of-;the
century and continues to the present. Channelization causes changes in water
velocity, reduces the width of the river, and prevents water flow into.
backwaters.. In the channelized reach downstream of Sioux City, Iowa,. the
Missouri River that was once a diverse assembledge of braided channels,
sandbars, and backwaters is now confined within a narrow channel of rather
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