My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
Pallid Sturgeon Recovery Plan
CWCB
>
Water Supply Protection
>
DayForward
>
5001-6000
>
Pallid Sturgeon Recovery Plan
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
4/8/2013 4:34:02 PM
Creation date
3/6/2013 2:34:12 PM
Metadata
Fields
Template:
Water Supply Protection
Description
related to the Platte River Endangered Species Partnership (aka Platte River Recovery Implementation Program or PRRIP),
State
NE
Basin
South Platte
Water Division
1
Date
11/7/1993
Author
Pallid Sturgeon Recovery Team, U.S. Fish and Wildlife Service
Title
Recovery Plan for the Pallid Sturgeon (Scaphirhynchus albus)
Water Supply Pro - Doc Type
Report/Study
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
64
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
there was a clear relationship between poor year class development in most <br />native species studied and the artificial hydrograph. <br />Before impoundment behind Missouri River reservoirs (1926 to 1952), peak <br />discharges generally occurred in April, and then again with a larger peak in <br />June (Pflieger and Grace 1987). Today, dam operations reduce flows from April <br />to July for flood control, and increase flows from July to April for <br />navigation, water supply, and hydropower. In addition to such seasonal shifts <br />in the flow patterns, main stem dams operating for daily hydropower needs can <br />cause daily fluctuations in water levels in tailwater areas by as much as 2 to <br />3 m (6.6 to 9.8 ft). This fluctuation can disrupt the macroinvertebrate <br />community and larval fish rearing areas for many miles downstream of the dam <br />by alternately flooding and dewatering habitats. <br />Modde and Schmulbach (1973) observed that factors affecting shovelnose <br />sturgeon prey availability within the unchannelized Missouri River include <br />temperature, seasonal recruitment, and changes in density influenced by the <br />timing and discharge rates from Gavins Point Dam. They hypothesized that the <br />reduction in numbers of shovelnose sturgeon may be due to reduced availability <br />of prey species caused by high discharges from Gavins Point Dam. <br />Before the Missouri River was channelized and impounded, it annually eroded <br />3.1 hectares /km of its floodplain (U.S. Army Corps of Engineers 1981). Most <br />of this erosion has stopped due to channelization and impoundment. Erosion <br />was a natural function of the river system, and through erosion, inorganic <br />sediments, organic matter, and large woody debris were introduced into the <br />river. This material import was essential to the habitat dynamics and <br />nutrient cycling of the river system. Such sediment and nutrient discharge <br />are the raw materials for habitat development in the Missouri and Mississippi <br />River system. Construction of dams eliminated 80 percent of this material. <br />Fremling (1989) reports that the sediment.load of the middle Mississippi River <br />has declined 66 percent from pre -1935 levels, mainly due to sediment <br />entrapment in Missouri River impoundments. This lack of sediment delivery <br />upset the natural channel equilibrium and was replaced by a variety of <br />nonequilibrium processes such as hydraulic sorting and bed paving, which <br />eventually will eliminate all sediment movement. This has already occurred to <br />some extent and has resulted in reduced bed roughness and, therefore, reduced <br />substrate diversity. This has reduced the reproductive success of substrate <br />spawners, such as sauger (Stizostedion canadense), sturgeon, and paddlefish <br />(Hesse and Mestl 1993b). <br />The turbidity caused by suspended sediment also provided the pallid sturgeon <br />and other native fish, adapted to living in a nearly sightless world, with <br />cover while moving from one snag or undercut bank to another. Today, water <br />clarity has increased dramatically, and this essential cover is gone. Under <br />such conditions, predation by sight- feeding predators, such as northern pike <br />(Esox lucius), walleye (Stizostedion vitreum), and smallmouth bass <br />(micropterus do7omieui), can be expected to significantly impact native <br />species not equipped by evolution with good eyesight. <br />12 <br />
The URL can be used to link to this page
Your browser does not support the video tag.