Link to U.S. Geological Survey Home Page

In cooperation with the National Park Service

Baseline Assessment of Instream and Riparian-Zone Biological Resources on the Rio Grande in and Near Big Bend National Park, Texas


By J. Bruce Moring

U.S. Geological Survey
Water-Resources Investigations Report 02–4106


Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at http://access.adobe.com/.

pdf version (78.3 MB)


Photograph showing the Rio Grande just downstream of Santa Elena Canyon in Big Bend National Park, August 1998 (photograph by Patrick O. Keefe, U.S. Geological Survey).

Contents

Abstract

Introduction

Methods of Assessment

Site Selection and Establishment

Stream-Habitat Assessment

Fish-Community Assessment

Benthic Macroinvertebrate Assessment

Data Management and Analysis

Results of Assessment

Stream Habitat

Fish Community

Benthic Macroinvertebrates

Summary

Selected References

 

FIGURES

     1. Map showing baseline biological assessment sites in and near Big Bend National Park, Texas

 2–6. Planimetric reach maps for:

              2. Rio Grande above Colorado Canyon

              3. Rio Grande below Santa Elena Canyon

              4. Rio Grande at Johnson Ranch

              5. Rio Grande above Boquillas Canyon  

              6. Rio Grande below Maravillas Creek (Black Gap Wildlife Refuge)

              7. Graph showing reach sinuosity for five bioassessment reaches in and near Big Bend National Park, Texas

              8. Graph showing reach slope for five bioassessment reaches in and near Big Bend National Park, Texas

 9–13. Boxplots showing:

              9. Streamflow velocity and selected stream-habitat measures for five bioassessment reaches in and near Big    
                  Bend National Park, Texas

            10. Bank height to channel width ratio for five bioassessment reaches in and near Big Bend National Park, Texas

            11. Embeddedness of cobble for five bioassessment reaches in and near Big Bend National Park, Texas

            12. Gravel and larger particle size of bed material for five bioassessment reaches in and near Big Bend National 
                  Park, Texas

            13. Bank vegetation coverage for five bioassessment reaches in and near Big Bend National Park, Texas

14–26. Graphs showing:

14. Relative abundance of selected species of bank vegetation for five bioassessment reaches in and near
      Big Bend National Park, Texas

15. Number of fish species for five bioassessment reaches in and near Big Bend National Park, Texas

16. Number of fish versus number of species for five bioassessment reaches in and near Big Bend
      National Park, Texas

17. Menhinick’s species richness for fish communities for five bioassessment reaches in and near Big
      Bend National Park, Texas

18. Results of cluster analysis to indicate similarity of fish communities for five bioassessment reaches in
      and near Big Bend National Park, Texas

19. Relative abundance of major fish families for five bioassessment reaches in and near Big Bend
      National Park, Texas

20. Relative abundance of major fish trophic groups for five bioassessment sites in and near Big Bend
      National Park, Texas

21. Results of cluster analysis to indicate similarity of benthic aquatic-insect communities for five
      bioassessment reaches in and near Big Bend National Park, Texas

22. Comparison of total aquatic-insect taxa and richest targeted habitat (RTH) aquatic-insect taxa for five
      bioassessment reaches in and near Big Bend National Park, Texas

23. Number of aquatic-insect taxa versus number of aquatic-insect individuals (richest targeted habitat
      [RTH] samples only) for five bioassessment reaches in and near Big Bend National Park, Texas

24. Mechanic's taxa richness for aquatic insects for five bioassessment reaches in and near Big Bend
      National Park, Texas

25. Relative abundance of ephemeroptera and trichoptera taxa (richest targeted habitat [RTH] samples
      only) for five bioassessment reaches in and near Big Bend National Park, Texas

26. Relative abundance of major aquatic-insect trophic groups (richest targeted habitat [RTH] samples
      only) for five bioassessment reaches in and near Big Bend National Park, Texas

 

TABLES

    1. Name, location, and general description of U.S. Geological Survey Rio Grande bioassessment reaches in and near
        Big Bend National Park, Texas

    2. Stream-habitat measures for bioassessment reaches on the Rio Grande in and near Big Bend National Park, Texas

    3. Fish taxa and individual counts of fish collected in the Rio Grande in and near Big Bend National Park, Texas

    4. Taxonomic classification of benthic macroinvertebrates and counts for individual taxa collected in the Rio Grande in
         and near Big Bend National Park, Texas

ABBREVIATIONS

cm, centimeters

km, kilometers

L, liters

m, meters

m/s, meters per second

m2, square meters

m3/s, cubic meters per second

µm, micrometers

mg/L, milligrams per liter

mm, millimeters


Abstract

Five study sites, and a sampling reach within each site, were established on the Rio Grande in and near Big Bend National Park in 1999 to provide the National Park Service with data and information on the status of stream habitat, fish communities, and benthic macroinvertebrates. Differences in stream-habitat conditions and riparian vegetation reflect differences in surface geology among the five sampling reaches. In the most upstream reach, Colorado Canyon, where igneous rock predominates, streambed material is larger; and riparian vegetation is less diverse and not as dense as in the four other, mostly limestone reaches. Eighteen species of fish and a total of 474 individuals were collected among the five reaches; 348 of the 474 were minnows. The most fish species (15) were collected at the Santa Elena reach and the fewest species (9) at the Colorado Canyon and Johnson Ranch reaches. The fish community at Colorado Canyon was least like the fish communities at the four other reaches. Fish trophic structure reflected fish-community structure among the five reaches. Invertivores made up at least 60 percent of the trophic structure at all reaches except Colorado Canyon. Piscivores dominated the trophic structure at Colorado Canyon. At the four other reaches, piscivores were the smallest trophic group. Eighty percent of the benthic macroinvertebrate taxa collected were aquatic insects. Two species of blackfly were the most frequently collected invertebrate taxon. Net-spinning caddisflies were common at all reaches except Santa Elena. The aquatic-insect community at the Boquillas reach was least similar to the aquatic-insect community at the other reaches.




U.S. Department of the Interior, U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/wri024106
Page Contact Information: GS Pubs Web Contact
Last modified: Friday, September 16 2005, 04:23:47 PM
FirstGov button  Take Pride in America button