This document summarizes a project that mapped riverine habitat in the Rio Grande to support the experimental reintroduction of the endangered Rio Grande silvery minnow. Researchers used high-precision GPS to map habitat types at different river flows. They collected data on physical characteristics and fish assemblages. The resulting spatial database will help understand habitat variability and fish distributions to aid conservation of the silvery minnow.

1. Mapping Instream Riverine Habitat Using High-
Precision GPS
A Project in Support of the Experimental Introduction of the Federally Endangered
Rio Grande Silvery Minnow (Hybognathus amarus) into the
Big Bend Reach of the Rio Grande
Daniel K. Pearson Bruce Moring
Geographer/GIS Specialist Senior Biologist
USGS Texas Water Science Center USGS Texas Water Science Center
Austin, Texas Austin, Texas
dpearson@usgs.gov jbmoring@usgs.gov
512.927.3561 512.927.3585
U.S. Department of the Interior
U.S. Geological Survey

2. Overview
 Background on Rio Grande silvery minnow
introduction
 Rationale and approach to river mapping
 GPS Data Collection
 Methods, equipment and musings
 Results and Data products

3. Project Support
 Funding for study USGS SSP, USFWS, MRGESP
Collaborative
Key Contacts –
 Aimee Roberson, Fish and Wildlife Biologist, Project
Lead, USFWS, Alpine, TX
 Jason Remshardt and staff, support for fish assemblage
survey, USFWS, Albuquerque, NM
 Rio Grande Silvery Minnow Technical Advisory Team
(USFWS, Texas Parks and Wildlife Service, UT-Pan
American University, Big Bend National Park, and USGS)
 Mickey Porter, Sarah Beck, USACE, Albuquerque, NM

4. Biology of Hybognathus amarus
 Historically found throughout the Rio Grande
and Pecos Basins. Population numbers
dropped after 1950s. Sustained population in
Middle Rio Grande, New Mexico
 Pelagic spawners, produce large numbers of
semi-buoyant eggs
 Prefer low-velocity habitat with sandy or silty
substrates
 Preferred habitats including side channels,
backwaters, and oxbows associated with a
meandering channel. Algal grazers.

5. Historical Change to Rio Grande
 Drivers of change
 Altered flow, peak flows and
sediment transport
 Aggrading and narrowing
channel
 Invasives (Salt cedar, exotic
river cane)
 Changes to flow contribution
from Rio Conchos
 Images: Taken near Black
Dike (Big Bend NP)
Dean and Schmidt, Role of feedback mechanisms in historic channel changes of the lower
Rio Grande in the Big Bend region., Geomorphology, 2010

6. RGSM Re-introduction to BBNP
 December 2008, silvery minnows were re-
introduced in the Rio Grande as a non-
essential experimental population under
section 10(j) of the Endangered Species Act
 1.43 million minnows released to date with 4
releases (2008-11), one additional release
(2012)
 Release sites – 1. Contrabando, 2. Santa
Elena (Terlingua Creek), 3. Rio Grande
Village, 4. Stillwell Crossing (Adam’s Ranch)

7. Release Sites/Study Area

8. Project Objectives
 River mapping and fish assemblage collocated with
release sites to understand variability among release
sites
 Determine the area, frequency, and physical
characteristics of in-channel river habitats at the
mesohabitat scale over a range of river flows.
 Determine how fish assemblage varies (composition
and distribution) among mesohabitat types and
between reaches over a range of river flows with
focus on Rio Grande silvery minnow population

9. Rationale for Mesohabitat Approach
 USFWS wanted a habitat component and fish assemblage
survey in the early stages of the introduction and in the context
of river flow!
Eco-hydraulic
Mesohabitat
River Distribution
Channel of
Geomorph. Aquatic
Biota
 “.…interest has grown in testing the hypothesis that significant
variation in assemblage among streams is explicable in terms of
hydrological patterns, which can vary substantially over short
geographic distances (Poff and Allen, 1995).”

10. Mesohabitat
 Our Mesohabitat Scheme: A priori classification of “eco-
hydraulic” habitats biased towards including more backwater
and slack-water habitats important for Rio Grande silvery
minnows and similar species.
Point bar
Eddy Pool
Inundated point bar
Riffle
` Run
 Mesohabitats used in this study include: backwater, forewater,
embayment, rapid, riffle, run/glide, pool (eddy, main channel and
isolated), submerged channel and point bars.

11. Selected River Flows
 Used IHA to determine target flows (Nature
Conservancy)
 Winter to spring low-flow target = 200 – 400
cfs
 Late spring to mid summer within-bank high
pulse = 500 – 1500 cfs
 Overbank flooding
flow = using peak of
fall 2008 event
(ca. 50,000 cfs)

12. GPS Data Collection
 Map and characterize instream habitat
(mesohabitat-scale approach)
 Create a detailed reach map at each targeted
flows using high-performance GPS receiver
in conjunction with high-resolution remotely
sensed imagery
 Create spatially enabled database to capture
geographic (map), physical habitat, fish
assemble and

13. Equipment
 Trimble® DSM™ 232 modular GPS receiver
 Omnistar Subcription (XP) - offers GPS correction
services that improves the accuracy of a GPS
receiver, allows sub-foot realtime positioning
 Fed directly in GIS (no post-processing)
 Panasonic Toughbook CF-19
 Hi Capacity External Laptop Battery

14. Mapping Methods
 Capture water’s edge on both banks was
mapped first creating a boundary for each site
 Next, each mesohabitat was mapped by
delineating its perimeter with the GPS receiver
mounted in a boat or in a backpack by wading
 Each mesohabitat (e.g., rapid, riffle, run, pool,
glide, embayment, backwater) edited and
stored on a field laptop as geo-referenced
polygons using ArcGIS

15. GPS used to capture water’s edge
Rio Grande @ Terlingua Creek

16. Complete delineations and attribute
Run
SCB
Pool
Run
Rio Grande @ Terlingua Creek

17. Results – Data Collection/Mapping
 FY 2010 Sampling
 low-flow target (200-400cfs)
 high-pulse flow target (500-1500cfs)
 Low-flow sampling divided by flash flood
event ~10,000cfs
 High-pulse flow mapping possible due to
sustained release from Rio Conchos dams
(MX)

21. More Results – Extreme low-flow
 FY 2011 Sampling
 West Texas and throughout under “Extreme
Drought”
 Capture “bottom out” flows – May 2011
 Historically low flows – 1st Qtr 2011
 No measureable rainfall since September 2010
 Full habitat assessment, mapping study
reaches and fish assemblage data

22. Low flows - May 2011

24. RAPID
RIFFLE
RUN
POOL
FOREWATER
BACKWATER
EMBAYMENT
SUBMERGED BAR

25. Lessons learned…
 Requires use of multiple flotation devices –
Canoe/Kayak, Zodiac, Human
 Effort to limit impact of our presence on
habitat
 Low flow mapping much easier than high-
pulse (wadeable)
 Putting equipment in harm’s way
 GPS – Marine unit
 Panasonic laptop – Water “resistant”

26. More…
 Laptop battery good for about 4 hours
 External gives us +6 hours
 Considered use of PDA but opted for
Toughbook for larger screen size
 Other GPS units would get us better accuracy
but drawbacks
 Cost/Time
 Post-processing/Direct feed into ArcGIS
 Current imagery source
 Maps exported to GeoPDF (iPad)

27. Physical Characterization - Habitat
•Depth, velocity, substrate, at
3 to 5 points in each
mesohabitat.
•Fish cover along 1-meter
wide bank-to-bank transect at
each point.
•Margin or near-shore habitat
at mid-point transect
evaluated for percent
periphyton cover and
dominant substrate using .25
m2 quadrat

28. Fish Assemblage – (Wadeable)
 One seine haul per mesohabitat randomly
selected from nine possible locations.
 Two or more seine hauls in some very large runs.
 Per seine haul
 Length, depth and velocity (center point),
dominant substrate, and counts per species
recorded.
Left bank Right bank
Mesohabitat

29. Guild Association – Velocity
H. amarus
N. braytoni

31. Project Data Model
 Geographic Data (GPS)  Tabular Data
 Polygons  Site information
 Low-pulse  Physical Measures
 High-pulse  Margin
 Extreme low-pulse
 Fish
 Points
 Sampling  Fish cover
 Lines  Fish habitat
 ADCP  Water quality
 Electrofishing
Relationship Class

32. How do we use this technology?
For RGSM Project:
 Project management of data resources
 Answer complex spatial queries
 Using GIS or via MS Access
 Data can be exported to other formats as needed
for analysis
 Web application development
 Online access
 Mapping components

33. Next Steps
 Complete data analysis and writing of USGS
Scientific Investigation Report and a journal
article this summer
 Online publication of project database
 In first year of similar study in Middle Rio
Grande (Albuq – Elephant Butte Reservoir) in
New Mexico

34. Questions?
http://tx.usgs.gov/projects/bigbend/mapping
SMhabitat.html
 Daniel Pearson – dpearson@usgs.gov
 Bruce Moring – jbmoring@usgs.gov