My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
8105
CWCB
>
UCREFRP
>
Copyright
>
8105
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
8/11/2009 11:34:21 AM
Creation date
5/22/2009 12:31:02 PM
Metadata
Fields
Template:
UCREFRP
UCREFRP Catalog Number
8105
Author
Haines, G. B., D. W. Beyers and T. Modde.
Title
Estimation of Winter Survival, Movement and Dispersal of Young Colorado Squawfish in the Green River, Utah.
USFW Year
1998.
USFW - Doc Type
Recovery Program Project 36,
Copyright Material
YES
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
18
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
<br />280 <br /> <br />Y.K. CONVERSE ET AL. <br /> <br />In this study, the association with cover is stronger than those with water velocity or depth in channel <br />margins. However, addressing the biological basis for the strong association with cover was beyond the <br />scope of this study. We suspect that the presence of cover affects local conditions of water depth and <br />velocity in channel margins. However, the distance of 2.5 m used in this study as a boundary for habitat <br />measurements along channel margins may have been too broad to detect associations between fish and <br />specific conditions of depth and velocity. Small fish are probably responding to conditions within 0.5-1 <br />m of the water's edge. If so, a stronger association between fish and velocity or depth may have been <br />masked by main channel hydraulic conditions. A better approach would be to analyze the physical <br />conditions only within the channel margin area that subadult humpback chub use, which may vary among <br />shoreline types, rather than a specific distance from shore. <br /> <br />Historic and present habitat condition <br /> <br />This study also demonstrated that mean depth, velocity and cover of shorelines vary with discharge <br />during base-flow conditions. Consequently, higher base flows, which occur a greater proportion of the <br />time in the current flow regime, may reduce subadult humpback chub habitat quality in natural habitats <br />compared with the same during pre-dam conditions in the Colorado River through Grand Canyon. <br />Reduced habitat quality may partially explain why subadults now use naturalized habitats, like vegetated <br />shorelines, which did not exist historically more than they use natural habitats like talus and debris fan <br />shorelines. <br />Vegetated shoreline habitat. Shoreline vegetation in Grand Canyon consists mainly of overhanging <br />tamarisk (Tamarix chinensis) that has stabilized sand deposits. Tamarisk is an exotic riparian plant that <br />has been present in the Colorado River since the early part of this century but was not able to stabilize <br />sand at the water's edge until the onset of flow regulation in 1962. Before that time, annual floods scoured <br />shorelines of any perennial vegetation, leaving extensive sand beaches (Turner and Karpiscak, 1980). <br />Relatively high use of vegetated shorelines by subadult humpback chub implies that subadults may <br />prefer these new areas over natural habitats, like talus or debris fans. Naturalized vegetation may be used <br />more than natural habitats for three reasons: (1) original shoreline conditions may have been modified by <br />flow regulation such that they currently provide only marginally acceptable conditions; (2) previously <br />important shoreline types are no longer present; or (3) vegetated shorelines simply provide better habitat <br />conditions than what naturally exist. Another possibility is that a combination of these conditions exists. <br />Modified shoreline conditions. Flow regulation may alter a suite of physical or biological shoreline <br />conditions, thereby limiting subadult humpback chub habitat quality. Changes in discharge cause basic <br />hydraulic changes in the river (Leopold et al., 1964). Before dam operations, base flows of the Colorado <br />River were two to five times less than the current average base flow. These results suggest that higher base <br />flows in the current flow regime increase mean depth and velocity and decrease cover. At-a-station <br />hydraulic geometry predicts that depth and velocity increase as discharge increases (Richards, 1977); <br />however, it is unclear why the occurrence of cover decreases with increasing discharge. <br />An examination of the cover/discharge relationship for individual shoreline types partially explains this <br />phenomenon. The presence of cover is the result of structural heterogeneity along the wetted perimeter of <br />the channel. The structure of bedrock, debris fan and talus shoreline types depends on morphology of <br />local geology and the shoreline angle of repose along the water's edge. These are geologically dependent <br />shoreline types. As basic geomorphology predicts (Leopold et al., 1964; Ritter, 1978), the angle of repose <br />decreases as colluvium accumulates at the toe of the slope. At higher discharges, the channel margins may <br />encounter more uniform or massive colluvium and higher angles of repose, or shoreline availability may <br />shift to more bedrock and sheer walls; consequently, structural heterogeneity would decrease with <br />increasing discharge among these shoreline types. <br />In contrast, cobble, sand and vegetation shoreline types are formed from main channel activity at high <br />discharges and are exposed as water levels recede. The structure of these shorelines is not as dependent <br />on local lithology; therefore, these shorelines are geologically independent. Because these shorelines are <br />formed by alluvial deposits, their structure and angle of repose at the water's edge is more homogeneous <br /> <br />@ 1998 John Wiley & Sons, Ltd. <br /> <br />Regul. Rivers: Res. Mgmt. 14: 267-284 (1998) <br /> <br /><. <br /> <br />~ <br /> <br />.. <br />
The URL can be used to link to this page
Your browser does not support the video tag.