A mesohabitat scale assessment of available in-channel 

habitat in relation to streamflows is considered by many ecologists 

and fluvial geomorphologists to be critical for the development of 

practical tools in river management (Harper and Everard, 1998; 

Newson and Newson, 2000), and the availability of functional 

habitat is essential for maintaining viable fish populations 

(Lapointe and others, 2013). Mesohabitats are visually distinct 

units of habitat within a stream with apparent uniformity (Pardo 

and Armitage, 1997; Parasiewicz, 2001) and with similar 

depth, velocity, slope, substrate, and cover. Mesohabitat-scale 

assessments provide information on habitat area as a function of 

alterations in river flow, channel planform, and other activities 

(Parasiewicz, 2001). 

Mesohabitat use by Rio Grande silvery minnows, along 

with the physical properties of depth, velocity, and substrate, 

have been the subject of previous studies (Dudley and Platania, 

1997; Dudley and others, 2012, 2013; Moring and others, 

2014); however, information on the spatial extent of available 

mesohabitats over a range of streamflows throughout the Middle 

Rio Grande remains sparse (Remshardt and Tashjian, 2003). To 

better understand the spatial extent of available mesohabitats over 

a range of streamflows, the U.S. Geological Survey (USGS), in 

cooperation with the U.S. Army Corps of Engineers, Albuquerque 

District, and the U.S. Fish and Wildlife Service New Mexico 

Fish and Wildlife Conservation Office in Albuquerque, N. Mex., 

evaluated physical characteristics and mapped mesohabitats 

associated with small-bodied fish assemblages during 2011–12 

during moderate and low streamflow at 15 sites on the Middle Rio 

Grande in New Mexico, in the reach between Cochiti Dam and 

Elephant Butte Reservoir. 

Introduction

From its headwaters in Colorado to its terminus 

at the Gulf of Mexico (fig. 1), the Rio Grande 

provides vital habitat to a variety of species adapted 

to its natural flood regime (Schmidt and others, 

2003). The Rio Grande is the second longest river in 

North America. The principal natural flood regime 

from the headwaters downstream to Presidio, Texas, 

is the result of snowmelt runoff between April and 

July in Colorado and New Mexico; downstream 

from Presidio, the natural flood regime is the result 

of summer thunderstorms (U.S. Army Corps of 

Engineers and others, 2007; Schmidt and others, 

2003). Native species in the Rio Grande, including 

Hybognathus amarus (Rio Grande silvery minnow) 

(fig. 2) and other small-bodied fish, are adapted to 

the natural flood regime of the Rio Grande (Sublette 

and others, 1990; Crawford and others, 1993). 

Background on this species and associated issues as 

well as a complete description of the study area can 

be found in the companion report to this one (Braun 

and others, 2015).

 Federally listed as an endangered species in 

1994 (U.S. Fish and Wildlife Service, 1994), the 

Rio Grande silvery minnow historically occupied 

about 4,000 kilometers (km) in the main stems of 

the Rio Grande and the Pecos River (fig. 1) (U.S. 

Fish and Wildlife Service, 2010). The decline of 

the Rio Grande silvery minnow throughout its 

historical range has been attributed to modifications 

of the natural streamflow regime, channel drying, 

construction of reservoirs and low-head diversion 

dams, stream channelization, declining water 

quality, and interactions with nonnative fish (Cook 

and others, 1992; Edwards, 2005; U.S. Fish and 

Wildlife Service, 2010). Natural populations of the 

Rio Grande silvery minnow currently (2015) are 

found only in the reach of the Rio Grande in N. Mex. 

that extends about 280 km between Cochiti Dam 

and Elephant Butte Reservoir (fig. 1) (U.S. Fish and 

Wildlife Service 2010; Gonzales and others, 2014), 

referred to as the “Middle Rio Grande” for the 

purpose of this report. 

Methods of Investigation

The physical characteristics and fish 

assemblage of stream mesohabitats were 

characterized within a 1-km length of stream 

channel at 15 sites distributed along the Middle 

Rio Grande and were selected starting about 

3 km downstream from Cochiti Dam and 

ending about 40 km upstream from Elephant 

Butte Reservoir (table 1, fig. 3). Sites along 

the Middle Rio Grande were grouped into four 

river reaches separated by diversion dams. In 

downstream order, the names of the diversion 

dams followed by short names of the sites 

(in parentheses) were Cochiti (Peña Blanca), 

Angostura (Bernalillo, La Orilla, Barelas, Los 

Padillas), Isleta (Los Lunas I, Los Lunas II, 

Abeytas, La Joya, Rio Salado), and San Acacia 

(Lemitar, Arroyo del Tajo, San Pedro, Bosque 

del Apache I, and Bosque del Apache II). The 

Cochiti, Angostura, and Isleta reaches are 

bound by upstream and downstream diversion 

dams (fig. 3), whereas there is a diversion dam 

at the upstream boundary of the San Acacia 

reach, but the downstream boundary of the 

reach is the upstream extent of Elephant Butte 

Reservoir. Stream habitat was mapped in the 

field by using a geographic information system 

(GIS) in conjunction with a Global Positioning 

System (GPS). The four reaches delineated 

in this report are also being assessed as part 

of the Middle Rio Grande Bosque Initiative 

(MRGBI). The MRGBI “is an ongoing, 

congressionally supported, interagency 

ecosystem management effort to coordinate 

activities related to the ecological restoration 

and management of the Middle Rio Grande” 

(U.S. Fish and Wildlife Service, 2014, p. 1).

U.S. Geological Survey site name

U.S. Geological

Survey site

number

Short name

MRGBI

reach

names1

Mapping

Fish and

aquatic

habitat

Fish and

aquatic

habitat

Fish and

aquatic

habitat

Mapping Mapping

Rio Grande nr Pena Blanca, N. Mex. 353330106213500 Peña Blanca PNB Cochiti Nov. 10 Nov. 11 -- -- -- --

Rio Grande dws Hwy 550 at Bernalillo, N. Mex. 351848106333400 Bernalillo BRN Angostura Nov. 11 Nov. 12 -- -- -- --

Rio Grande ups Montano Rd NW at Albuquerque, N. Mex. 350859106402600 La Orilla LOR Angostura Nov. 16 Nov. 17 -- -- Aug. 11 Aug. 13

Rio Grande ups Hwy 314 at Albuquerque, N. Mex. 350432106400500 Barelas BAR Angostura Nov. 9 Nov. 10 -- -- Aug. 10 Aug. 11

Rio Grande ups I-25 nr Los Padillas, N. Mex. 345732106410800 Los Padillas PAD Angostura Nov. 15 Nov. 16 -- -- Aug. 9 Aug. 10

Rio Grande ups Hwy 6 at Los Lunas, N. Mex. 344852106424200 Los Lunas I LL1 Isleta Nov. 12 Nov. 14 -- -- June 5 June 6

Rio Grande nr Los Chavez, N. Mex. 344457106443300 Los Lunas II LL2 Isleta Nov. 14 Nov. 15 -- -- June 6 June 7

Rio Grande ups Hwy 60 nr Contreras, N. Mex. 342644106481300 Abeytas ABY Isleta Nov. 28 Nov. 29 -- -- June 7 June 8

Rio Grande nr La Joya, N. Mex. 341842106511100 La Joya LJY Isleta Nov. 29 Nov. 30 -- -- Aug. 8 Aug. 9

Rio Grande dws Arroyo Rosa de Castillo, San Acacia 341542106520700 Rio Salado RSL Isleta Nov. 30 Dec. 1 -- -- Aug. 7 Aug. 8

Rio Grande nr Lemitar, N. Mex. 341044106530300 Lemitar LEM San Acacia Dec. 1 Dec. 2 -- -- Aug. 6 Aug. 7

Rio Grande dws Arroyo del Tajo nr Socorro, N. Mex. 340215106515500 Arroyo del Tajo ATJ San Acacia Dec. 1 Dec. 3 -- -- June 8 June 9

Rio Grande dws Hwy 380 nr San Antonio, N. Mex. 335403106505800 San Pedro SPD San Acacia 2

Dec. 3 2Dec. 6 2Feb. 6 2Feb. 7 June 9 June 11

Rio Grande N of Bosque del Apache, San Antonio, N. Mex. 335229106505800 Bosque del Apache I BA1 San Acacia -- -- 2

Feb. 7 2Feb. 8 June 11 June 12

Rio Grande at Bosque del Apache nr San Antonio, N. Mex. 334833106512200 Bosque del Apache II BA2 San Acacia 2

Dec. 6 -- 2Feb. 8 2Feb. 9 June 12 June 13

1

2

MRGBI reach names are from U.S. Fish and Wildlife Service (2014); colors associated with reaches are used throughout the report. Inclement weather made accurate mapping and representative fish sampling impossible. As a result, the San Pedro, Bosque del Apache I, and Bosque del Apache II sites were revisited

 in February 2012, when weather conditions were more suitable. 

[MRGBI, Middle Rio Grande Bosque Initiative; nr, near; dws, downstream from; ups, upstream from; --, no data were collected during this time period]

Dates sampled

November–December 2011 February 2012 July–August 2012

Map

identifier

Table 1. Study sites and sampling dates in the Middle Rio Grande,New Mexico, 2010–11 (reach names are from U.S. Fish and Wildlife Service, 2014).

BIG BEND

NATIONAL PARK

BIG BEND RANCH

STATE PARK

TEXAS

U.S. part

of the Rio

Grande Basin

Map

extent

COLORADO NEW MEXICO

COCHITI DAM

ELEPHANT BUTTE DAM

MULATO DAM

FOSTER’S WEIR

Lake

Sumner

Red Bluff

Reservoir

Amistad

Reservoir

Falcon

Reservoir

Elephant Butte

Reservoir

Caballo

Reservoir

Cochiti

Lake

Rio Chama

River

Pecos River Rio Grande

GULF OF

MEXICO

Albuquerque

Santa

Rosa

Socorro

Roswell

El Paso

Presidio

Pecos

Del Rio

Laredo

0 50 100 MILES

0 50 100 KILOMETERS

100 ̊

100 ̊

105 ̊

105 ̊

35 ̊

35 ̊

30 ̊ 30 ̊

EXPLANATION

Historical distribution

Current (2015) natural distribution

 (U.S. Fish and Wildlife Service, 2010)

Current (2015) reintroduced distribution (U.S. Fish

 and Wildlife Service, 2010)—Based on

 reintroduction initiated in December 2008

Base modified from U.S. Geological Survey

1:2,000,000-scale digital data

Universal Transverse Mercator projection, zone 13

North American Datum of 1983 

TEXAS

NEW MEXICO

MEXICO

Figure 1. Historical and current distribution of Hypognathus amarus (Rio Grande silvery minnow) in the 

Rio Grande and Pecos River, New Mexico and Texas.

Figure 2. Nursery raised Hybognathus amarus (Rio 

Grande silvery minnow) with tagged dorsal fin; colored 

dorsal fin tag was attached for identification purposes 

and corresponds to the reach of the Middle Rio Grande 

in which it was released. 

Purpose and Scope

This report documents differences in the mapped spatial extents 

and physical characteristics of in-channel fish habitat evaluated at the 

mesohabitat scale during winter 2011–12 (moderate streamflow) and 

summer 2012 (low streamflow) at 15 sites on the Middle Rio Grande in 

New Mexico starting about 3 km downstream from Cochiti Dam and 

ending about 40 km upstream from Elephant Butte Reservoir (fig. 3). 

The results of mesohabitat mapping, physical characterization, and fish 

assemblage surveys are summarized from the data that were collected. The 

report also presents general comparisons of physical mesohabitat data, such 

as wetted area and substrate type, and biological mesohabitat data, which 

included fish assemblage composition, species richness, Rio Grande silvery 

minnow relative abundance, and Rio Grande silvery minnow catch per 

unit effort. Selected water-quality properties (water temperature, specific 

conductance, dissolved oxygen, and pH) that were collected during lowflow conditions were published and analyzed in Braun and others (2015) 

and are not discussed in this report. 

NEW MEXICO

Area enlarged

0 20 40 MILES

0 20 40 KILOMETERS

Base modified from U.S. Geological Survey

1:1,000,000-scale digital data

Universe Transverse Mercator zone 13 projection

North American Datum of 1983 

EXPLANATION

Middle Rio Grande Bosque Initiative

 (MRGBI) reach names (tables 1 and 3)

 Cochiti reach

 Angostura reach

 Isleta reach

 San Acacia reach

Map identifiers followed by short

 names for sampling sites (table 1)

 PNB - Peña Blanca

 BRN - Bernalillo

 LOR - La Orilla

 BAR - Barelas

 PAD - Los Padillas

 LL1 - Los Lunas I

 LL2 - Los Lunas II

 ABY - Abeytas

 LJY - La Joya

 RSL - Rio Salado

 LEM - Lemitar

 ATJ - Arroyo del Tajo

 SPD - San Pedro

 BA1 - Bosque del Apache I

 BA2 - Bosque del Apache II

Sampling site and map identifier (table 1)

Lower San Juan Riverside Drain

U.S. Geological Survey streamflow-gaging station

 and station number

PNB

08317400 ¤£66

£¤285

£¤285

£¤380

£¤60

£¤550

£¤64

UV96

VU55

UV549

UV6

UV107

£¤550

*-25

*-40

-*25 Cochiti reach

Angostura reach

Isleta reach

San Acacia reach Rio

Grande

Jemez Ri ver

Rio

Puerco

Ala

mosa Creek

ArroyoComanche

Rio

Gallina

Jemez River

Rio Salado

Rio Chama

El Rito

Galisteo Creek

RioTusas

SantaFe Ri v er

Elephant Butte

Reservoir

BOSQUE DEL APACHE

NATIONAL WILDLIFE REFUGE 

SAN ALAMEDA BRIDGE

Lower San Juan

Riverside Drain

LL1

BRN

SPD

LEM

LJY

ATJ

PAD

ABY

RSL

PNB

BA1

LOR

BAR

BA2

LL2

08317400

08319000

08329918

08329928

08330000

08331160

08331510

08355050

08355490

ANGOSTURA

DIVERSION DAM

COCHITI

DAM

ISLETA

DIVERSION

DAM

SAN ACACIA

DIVERSION

DAM

JEMEZ

CANYON

DAM

Los Lunas

Tierra

Amarilla

Bernalillo

Los Alamos

Alameda

Bosque Farms

Escondida

Los Padillas

La Joya

San Acacia

San Antonio

Lemitar

Santa Fe

Albuquerque

Socorro

107°30'

107°00' 106°30' 106°00'

36°30'

35°30'

35°00'

34°30'

34°00'

33°30'

36°00'

08330875

SANDOVAL

COUNTY

BERNALILLO

COUNTY

VALENCIA

COUNTY

SOCORRO

COUNTY

RIO ARRIBA

COUNTY

SANTA FE

COUNTY

LOS ALAMOS

COUNTY

Figure 3. Sites where mesohabitats were assessed and Middle Rio Grande Bosque Initiative reaches on the Middle Rio Grande in New Mexico, 2011–12. 

Description of Study Area

Braun and others (2015) provided a detailed description of 

the Middle Rio Grande; a brief description is provided herein. 

The Middle Rio Grande is an arid part of the Rio Grande Basin 

dependent on inflows from upstream. Historically, discharge 

in the Middle Rio Grande fluctuated between seasonal peaks 

from snowmelt runoff and from localized thunderstorms in 

the spring and early summer (U.S. Army Corps of Engineers 

and others, 2007) to periods of river fragmentation during 

late summer when some river segments would go dry (Tetra 

Tech, Inc., 2014). Today, the Middle Rio Grande is a highly 

regulated system influenced by numerous storage and flood 

control reservoirs, low-head diversion dams, and almost 1,500 

km of irrigation canals and drainages between Cochiti Dam 

and Elephant Butte Reservoir. Dams, diversions, and canals 

have not altered the preregulation seasonal streamflow pattern 

(fig. 4) but have dampened the magnitude and duration of 

extreme streamflow events and have led to extended periods 

when the river is dry downstream from Albuquerque during 

the summer to the early fall irrigation period (U.S. Bureau of 

Reclamation, 2012). 

The channel planform of the Middle Rio Grande has 

changed during the last 100 years from a braided aggrading 

channel to one that is mostly degrading, transitioning from 

a braided, sand-bed channel to a narrower, single-threaded 

channel that is dominated by a gravel bed through much of its 

length (Makar and AuBuchon, 2012). Between 1935 and 1989, 

the river channel area of the Middle Rio Grande decreased 

by about 50 percent (Crawford and others, 1993). Channel 

narrowing can be attributed to reductions in sediment supply, 

changes in peak spring flows caused by upstream flood control, 

channelization activities, and other river training actions used 

to manage flows for irrigation purposes (Makar and Aubuchon, 

2012). The effects of changes in the Rio Grande planform on 

native fish species were summarized by Schmidt and others 

(2003, p. 25–26):

Historically, the Rio Grande had a mobile bed and erodible 

banks, and the channel changed from year to year. Today’s 

channel is smaller, more stable, changes less from year to 

year, and infrequently inundates its former floodplain.*** 

The Rio Grande silvery minnow is adapted to the former 

wide shallow braided channel and associated habitats, and 

its population has declined greatly in response to channelization and diminished flows.

Daily mean discharge, in cubic feet per second (ft3/s)

LOR, 746 ft3/s (Nov. 17)

LOR, 430 ft3

/s (Aug. 13)

C

BRN, 570 ft3/s (Nov. 12)

B

PNB, 552 ft3/s (Nov. 11)

A

ABY, 940 ft3/s (Nov. 29)

LEM, 921 ft3

/s (Dec. 2)

RSL, 970 ft3

/s (Dec. 1)

LJY, 991 ft3

/s (Nov. 30)

LEM-4.13 ft3

/s (Aug. 7)

LJY, 49.5 ft3

/s (Aug. 9)

RSL, 37.9 ft3

/s (Aug. 8)

ABY, 179 ft3

/s (June 8)

F

LL1, 258 ft3

/s (June 6)

LL2, 243 ft3

/s (June 7)

LL1, 749 ft3

/s (Nov. 14)

E

PAD, 851 ft3/s (Nov. 16)

PAD, 334 ft3

/s (Aug. 10)

D

SPD, 68.3 ft3/s (June 11)

BA2, 45.7 ft3

/s (June 13)

BA1, 48.0 ft3/s (June 12)

SPD, 857 ft3

/s (Dec. 6)

BA1, 633 ft3/s (Feb. 8)

BA2, 588 ft3

/s (Feb. 9)

H

November December January February March April May June July

2011

August

2012

November December January February March April May June July

2011

August

2012

ATJ,140 ft3

/s (June 9)

ATJ, 870 ft3

/s (Dec. 3)

G

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

2,000

2,500

1,500

1,000

500

0

Measured discharge at sampling sites

EXPLANATION

Peña Blanca, PNB Daily mean discharge

Bernalillo, BRN

La Orilla, LOR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

Figure 4. Measured discharge at sampling sites and daily mean discharge at U.S. Geological Survey streamflow-gaging stations on the Middle Rio Grande, New Mexico. A, 08317400 Rio Grande below 

Cochiti Dam, N. Mex.; B, 08319000 Rio Grande at San Felipe, N. Mex.; C, 08329928 Rio Grande at Alameda, N. Mex.; D, 08330000 Rio Grande at Albuquerque, N. Mex.; E, 08331160 Rio Grande near Bosque farms, 

N. Mex.; F, 08331510 Rio Grande at State Highway 346 near Bosque, N. Mex.; G, 08355050 Rio Grande at bridge near Escondida, N. Mex.; and H, 08355490 Rio Grande above U.S. Highway 380 near San Antonio,

N. Mex.; November 1, 2011–August 31, 2012. 

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/110.3133/sim3350.

Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 1 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service
U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 2 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service

Fish Collection

Fish assemblage surveys 

were done at each sampling site 

(except at the Peña Blanca and 

Bernalillo sites during summer 

2012) at moderate and low 

streamflows. Mesohabitat types 

were subsampled (with targeted 

minimums of 20 mesohabitats per 

sampling site in winter 2011–12 

and 30 mesohabitats per sampling 

site in summer 2012) in proportion 

to their relative abundance at each 

reach. If three or fewer of a given 

mesohabitat type occurred in a 

sampling site, then all mesohabitats 

of that type were typically sampled. 

Fish were collected by using a 

seine while wading during both 

winter and summer sampling. 

The sampling approach was the 

same as the sampling approach 

described in Moring and others 

(2014) and was deliberately 

biased toward collecting fish from 

shallow, low-velocity, nearshore 

habitats preferred by Rio Grande 

silvery minnow and similar fish; 

for example, 3.0-millimeter mesh 

seines were used, as opposed to 

a larger mesh size, to increase 

the likelihood of collecting Rio 

Grande silvery minnow and other 

minnow species. Additional 

details on the fish assemblage 

surveys are provided in Braun 

and others (2015).

Physical Characteristics Over a Range of Streamflows

Physical characteristics 

including stream velocity, depth, 

and substrate type associated 

with different mesohabitats 

were measured over a range 

of streamflows. Instantaneous 

discharge measurements were 

made at most sites in accordance 

with standard USGS discharge 

measurement methods (Rantz 

and others, 1982; Turnipseed and 

Sauer, 2010). At the Barelas site on 

November 10, 2011, and August 11, 

2012, and the Los Lunas II site on 

November 15, 2011, the daily mean 

discharge was obtained from the 

USGS National Water Information 

System (NWIS) for the nearest 

upstream USGS streamflow-gaging 

station (table 1). Instantaneous 

discharge measurements were 

stored in NWIS (U.S. Geological 

Survey, 2014). 

During summer 2012, stream 

velocity and depth were recorded at 

the centroid of each seine haul by 

the crew of technicians collecting 

fish, whereas stream velocity, 

depth, dominant substrate type and 

size, and percent embeddedness 

were recorded during winter 

2011–12 and summer 2012 by 

a second crew of technicians 

who were collecting mesohabitat 

data along randomly selected 

transects within each sampled 

mesohabitat. Additional details 

on the mesohabitat data collection 

methods are provided in Braun 

and others (2015). Velocity and 

depth measurements were made 

by wading the stream with a 

FlowTracker hand-held acoustic 

Doppler velocimeter attached to 

a wading rod (SonTek, 2013). 

Standard USGS protocols 

for measuring velocity were 

followed (Rantz and others, 1982; 

Turnipseed and Sauer, 2010). 

Additional details on the velocity 

measurements are provided in 

Braun and others (2015).

Fish Assemblage Composition

Fish Assemblage Composition 

and Mapped Mesohabitat 

Features

By evaluating fish assemblage 

composition (that is, the number of 

individuals of each species collected either 

at a given sampling site or reach containing 

one or more sampling sites) over a range of 

streamflows during different times of the 

year, insights can be gained into the types 

of mesohabitats used by different species, 

including the Rio Grande silvery minnow, 

and how differences in the number of 

mapped mesohabitats and number of types 

of mesohabitats (depending on the amount 

of streamflow) correspond to changes in fish 

assemblages. 

The average number of fish collected per site during the winter and summer 

sampling periods in each of the four reaches (Cochiti, Angostura, Isleta, and San 

Acacia) was determined by dividing the total number of fish collected per reach by the 

number of sites sampled per reach. The average number of fish collected decreased 

in the downstream direction during winter 2011–12, when the average number of 

fish collected was 1,394 in the Cochiti reach (based on a single sampling at the only 

site in the Cochiti reach, the Peña Blanca site), 154 in the Angostura reach, 97 in the 

Isleta reach, and 39 in the San Acacia reach (table 3). During summer 2012, the site 

in the Cochiti reach was not sampled, and only 3 of the 4 sites in the Angostura reach 

were sampled (the Bernalillo site was not sampled). In the three reaches sampled 

during summer 2012, substantially more fish were collected on average in each reach 

compared to winter 2011–12, with summer averages of 593 fish in the Angostura reach, 

946 fish in the Isleta reach, and 697 fish in the San Acacia reach. 

 In the three reaches sampled in both the winter and summer, the average number 

of species collected per sampling site was higher in summer 2012 compared to winter 

2011–12. The average number of species collected per sampling site within each reach 

generally decreased between the upstream and downstream reaches in both winter 

2011–12 (6.5, 4.4, and 2.2, respectively, in the Angostura, Isleta, and San Acacia 

reaches) and summer 2012 (8.0, 8.0, and 7.2, respectively, in the Angostura, Isleta, and 

San Acacia reaches). The Angostura reach likely maintains greater fish diversity in part 

because it maintains a more consistent discharge relative to the reaches downstream and 

does not go dry from year to year.

The relative abundance of Rio Grande silvery minnows, calculated as the number 

of Rio Grande silvery minnows collected at a sampling site during a sampling period 

(winter 2011–12 or summer 2012) divided by the total number of Rio Grande silvery 

minnows collected at all sampling sites during the same sampling period, was highest in 

the San Acacia reach during 

both winter 2011–12 (about 

62 percent) and summer 

2012 (about 54 percent). 

The relative abundance of 

Rio Grande silvery minnows 

was higher in the Angostura 

reach (about 26 percent) 

in winter 2011–12 than in 

the Isleta reach (about 12 

percent), but the reverse 

was true in summer 2012, 

when the relative abundance 

was about 41 percent in 

the Isleta reach and about 

5 percent in the Angostura 

reach. No Rio Grande silvery 

minnows were collected at 

the Peña Blanca site in the 

Cochiti reach during the one 

time it was sampled (winter 

2011–12). 

The catch per unit 

effort of Rio Grande silvery 

minnows (RCPUE) was 

calculated by dividing the 

number of Rio Grande 

silvery minnows collected 

at a sampling site during 

a sampling period (winter 

2011–12 or summer 2012) 

by the sum of the total area 

seined (in square meters 

[m2]); the resulting quotient 

was multiplied by 100 m2 to 

obtain the RCPUE. The use 

of RCPUE to standardize 

fish data allows for direct 

comparisons between stream 

reaches or mesohabitats of 

different sizes (Nielsen and 

Johnson, 1983). The RCPUE

was highest on average per 

sampling site in the San 

Acacia reach during both 

winter 2011–12 (2.91) and 

summer 2012 (0.20). Like 

the relative abundance, the 

average RCPUE per site 

was higher in the Angostura 

reach (1.33) in winter 

2011–12 compared to the 

Isleta reach (0.47), but the 

reverse was true in summer 

2012, when the RCPUE was 

0.14 in the Isleta reach and 

0.03 in the Angostura reach. The RCPUE was substantially higher in winter 2011–12 

relative to summer 2012 because not only were there far more Rio Grande silvery 

minnows caught in winter 2011–12 (163) than in summer 2012 (22), but the seined area 

tended to be higher in summer 2012 because of a change in methodology between the 

two sampling events (as many as 20 mesohabitats were selected for seining in winter 

2011–12 as compared to 30 mesohabitats in summer 2012). The RCPUE in the Cochiti 

reach was 0 percent in winter 2011–12 because no Rio Grande silvery minnows were 

collected at the Peña Blanca site.

Among all sampling sites, the highest fish-species richness for the winter sampling 

period was measured at the Abeytas site (9 species); the highest fish-species richness 

for the summer sampling period was measured at the Los Lunas I site (10 species). 

The lowest fish-species richness for the winter sampling period was measured at 

the Los Lunas II and Bosque del Apache II sites (one species each); the lowest fishspecies richness for the summer sampling period was measured at the Rio Salado site 

(five species) (table 3). In all cases, the number of species collected at each sampling 

site in winter 2011–12 was less than (or equal to, in the case of the Los Padillas and 

Abeytas sites) the number of species collected at the same sampling site in summer 

2012. In all cases, the total number of fish collected at each sampling site in winter 

2011–12 was less than the number of fish collected 

at the same sampling site in summer 2012. In winter 

2011–12, the most fish were collected at Peña Blanca 

(1,394), and the least were collected at Los Lunas 

II (1); whereas in summer 2012, the most fish were 

collected at Lemitar (1,729), and the least were 

collected at San Pedro (269). It stands to reason 

that there would be greater species richness and 

a larger number of fish collected in summer 2012 

relative to winter 2011–12 because lower flows (and 

subsequently shallower mesohabitats) in summer 

2012 increased the likelihood of seining success. 

Not only is seining easier at shallow depths (because 

of the potential for increased speed and mobility 

from the crew of technicians collecting fish), but the 

overall fish density for each sampling site is also 

higher in the summer (assuming the number of fish 

remains relatively consistent) because the volume 

of water in which the fish are confined is smaller. 

However, it should be noted that the fishing effort 

was commensurate with the number of mesohabitats 

sampled for fish. In most cases, the number of 

mesohabitats sampled for fish increased from about 

20 in winter 2011–12 to about 30 in summer 2012. 

Fewer than 20 mesohabitats were mapped in winter 

2011–12 at Bernalillo (17), La Joya (18), and Lemitar 

(16) (fig. 7), so the number of mesohabitats where 

fish were collected was less than 20 at these three 

sites. 

To account 

for differences 

in sampling 

effort between 

winter 2011–12 

and summer 

2012 associated 

with differences 

in the number 

of mesohabitats 

seined, relative 

abundances 

of Rio Grande 

silvery minnows 

were calculated 

for each of the 

sampling sites 

during both 

winter 2011–12 

and summer 

2012 (table 3). 

The highest 

relative abundance of Rio Grande silvery minnows during winter 2011–12 occurred at 

Arroyo del Tajo (46.0 percent) followed by La Orilla (12.9 percent). Conversely, no 

Rio Grande silvery minnows were collected at 3 of the 15 sites sampled (Peña Blanca, 

Los Lunas II, and Abeytas) during winter 2011–12. The highest relative abundance of 

Rio Grande silvery minnows during summer 2012 occurred at Lemitar (45.5 percent) 

followed in succession by Los Lunas I (22.7 percent) and Los Lunas II (18.2 percent). 

Conversely, no Rio Grande silvery minnows were collected at 7 of the 13 sites sampled 

(La Orilla, Los Padillas, Abeytas, La Joya, Rio Salado, Bosque del Apache I, and 

Bosque del Apache II) during summer 2012. 

At the mesohabitat scale, Rio Grande silvery minnows were collected in 6 of the 

8 mesohabitat types mapped in this study (table 4). Rio Grande silvery minnows were 

collected most often in runs (101 individuals from 35 mesohabitats), followed by flats 

(32 individuals from 9 mesohabitats) and pools (28 individuals from 9 mesohabitats). 

The RCPUE by mesohabitat type was highest in pool mesohabitat types (1.44), 

followed by riffles (1.06) and runs (0.77).

Table 4. Rio Grande silvery minnow collection information based on mesohabitat type in the Middle Rio Grande, 

New Mexico, 2011–12.

[RGSM, Rio Grande silvery minnows; m2, square meters; RCPUE, catch per unit effort; —, not applicable because no RGSM were 

collected in these mesohabitat types]

Mesohabitat 

type

Number of

mesohabitats 

where RGSM 

were collected

Number of RGSM

collected in each

mesohabitat type

Number of seine 

hauls made in each

mesohabitat type

Total area 

seined (m2) RCPUE1

riffle 6 13 47 1,227 1.06

run 35 101 458 13,161 0.77

pool 9 28 97 1,941 1.44

isolated pool 2 5 52 930 0.54

forewater 0 0 10 324 —

backwater 1 6 66 1,521 0.39

embayment 0 0 21 654 —

flat 9 32 237 6,185 0.52

1

Calculated as the number of RGSMs collected within a given mesohabitat type divided by the total area (in square meters) seined 

within that mesohabitat type × 100. 

Mapped Mesohabitat Features

The total number and number of types of mesohabitats were generally 

larger at sampling sites during summer 2012, when streamflows were low, 

compared to winter 2011–12, when streamflows were moderate. During 

summer, streamflow also tended to decrease in the downstream direction in 

the study area. Decreases in streamflow in the summer compared to the winter 

typically led to increases in channel complexity in terms of the number 

of different wetted mesohabitat types present (fig. 7A), total number of 

mesohabitats present (fig. 7B), and the number of channel bars mapped (fig. 

7C). Decreases in streamflow also led to reductions in wetted area at all of the 

sampling sites that were mapped in both winter 2011–12 and summer 2012 

(fig. 7D). Summary statistics associated with winter 2011–12 are based on 

maps generated in November and December 2011 as well as February 2012. 

For sampling sites that were mapped more than once during winter 2011–12 

(San Pedro and Bosque del Apache II), the data associated with sampling in 

February 2012 was used in the calculation of summary statistics because the 

data were accompanied by the collection of physical habitat and fish data, 

whereas no such data were collected in association for San Pedro and Bosque 

del Apache II from December 2011 because of inclement weather. 

Decreases in streamflow between winter 2011–12 and summer 2012 

also led to decreased wetted areas of mesohabitats that were mapped at each 

sampling site. Sampling sites in the lower part of the Angostura reach and 

the upper part of the Isleta reach that pass through or near the city limits 

of Albuquerque, N. Mex., remain perennially wet throughout the year. Six 

sampling sites within these reaches (La Orilla, Barelas, Los Padillas, Los 

Lunas I, Los Lunas II, and Abeytas) had the largest wetted area for the winter 

2011–12 period, and 5 of these 6 sites had the largest wetted area for the 

summer 2012 period (fig. 7D). The wide channel conditions and sustained 

flow at the Barelas site produced the largest wetted areas (113,199 m2 during 

winter 2011–12 and 103,094 m2 during summer 2012) of all sampling 

sites. The greatest difference between wetted areas at a single sampling site 

between winter 2011–12 and summer 2012 was measured at the Abeytas site, 

where a difference in wetted area of 60,314 m2 was measured. The smallest 

wetted area in winter 2011–12 was measured at the Bernalillo site (37,144 

m2), whereas the smallest wetted area in summer 2012 was measured at the 

Lemitar site (13,547m2).

Table 2. Description of mesohabitat types used to describe the study sites as defined by observations and 

physical parameters measured over the course of the study.

[Mesohabitat types and descriptions are modified from Platania (1993)]

Mesohabitat type Description

Riffle Relatively shallow and low to moderate velocity feature characterized by moderately 

turbulent water

Run Relatively high velocity feature with laminar flow and a non-turbulent surface

Pool Feature with little or no velocity that may be deep in places

 Channel Type of pool where current moves in the same flow direction as the channel

 Eddy Type of pool where current moves in the opposite direction relative to flow

Isolated Pool Type of pool that is separate from the main channel; frequently a portion of a former 

backwater or forewater that has become disconnected from a secondary channel

Forewater Slackwater feature oriented into the principal direction of flow

Backwater Slackwater feature oriented in an opposing direction to the principal flow direction

Embayment Slackwater feature located adjacent to the channel and oriented perpendicular to flow

Flat Very shallow, low velocity feature typically located on the periphery of an existing point or 

channel bar; caused by a slight rise in stage

Point Bar Crescent-shaped depositional feature located on the inside of a stream bend; typically either 

devoid of or containing annual vegetation

Channel Bar Transitory parcel of land surrounded by water; typically either devoid of or containing 

annual vegetation

Table 3. Relative abundance of Rio Grande silvery minnows collected during sampling events in winter 2011-12 and summer 2012 on

the Middle Rio Grande, New Mexico.

[MRGBI, Middle Rio Grande Bosque Initiative; RGSM, Rio Grande silvery minnow; CPUE, catch per unit effort; m2, square meters; —, no data were collected 

during this time period] MRGBI Reach Name

Short Name

Winter 2011–12 Summer 2012

Relative

abundance

of 

RGSM1,

in percent

CPUE 

for 

RGSM2

Fish 

species 

richness3

Number of 

RGSM 

collected

Total 

number 

of fish 

collected

Total

area

seined

(m2)

Relative

abundance

of 

RGSM1,

in percent

CPUE 

for 

RGSM2

Fish 

species 

richness3

Number of 

RGSM 

collected

Total 

number 

of fish 

collected

Total

area

seined

(m2)

Cochiti Peña 

Blanca 0 0 4 0 1,394 661 — — — — — —

Aggostura

Bernalillo 1.23 0.38 8 2 450 531 — — — — — —

La Orilla 12.9 2.82 6 21 107 744 0 0 8 0 479 1,089

Barelas 7.98 1.03 5 13 23 1,259 4.55 0.08 9 1 530 1,254

Los Padillas 4.29 1.10 7 7 34 634 0 0 7 0 770 1,185

 Isleta

Los Lunas I 2.45 0.58 3 4 29 693 22.7 0.35 10 5 1,490 1,442

Los Lunas 

II 0 0 1 0 1 651 18.2 0.35 9 4 817 1,155

Abeytas 0 0 9 0 165 717 0 0 9 0 1,216 1,176

La Joya 0.61 0.18 5 1 218 564 0 0 7 0 791 924

Rio Salado 8.59 1.58 4 14 74 885 0 0 5 0 417 780

 San Acacia

Lemitar 7.98 2.46 3 13 57 529 45.5 0.88 8 10 1,729 1,142

Arroyo del 

Tajo 46.0 10.3 3 75 125 729 4.55 0.07 8 1 290 1,416

San Pedro 3.07 0.68 2 5 6 738 4.55 0.08 7 1 269 1,314

Bosque del 

Apache I 1.23 0.27 2 2 3 735 0 0 6 0 528 1,002

Bosque del 

Apache II 3.68 0.82 1 6 6 735 0 0 7 0 670 1,260

1

Calculated as the number of RGSMs collected at a site during a sampling period divided by total number of RGSMs collected at all sites during the same sampling period multiplied by 

100. Percentages may not sum to 100 because of rounding differences.

2

Calculated as the number of RGSMs collected at a site during a sampling period divided by the total area (in square meters) seined multiplied by 100. 

3

Total number of species collected.

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.

Mesohabitat Assessments Sampling Assessments and 

Streamflow 

During this study, 13 of the 15 sites were 

assessed under two different seasonal streamflow 

regimes during winter 2011–12 and summer 2012 

(table 1, fig. 4); the two remaining sites (Peña 

Blanca and Bernalillo) were only assessed in 

winter 2011–12. Mesohabitats were mapped and 

sampled during a period of moderate streamflow 

between November 2011 and February 2012 and 

during a period of low streamflow between June 

and August 2012 (table 1; fig. 4). In winter 2011–

12, sites were sampled generally from upstream 

to downstream, whereas in summer 2012, sites 

were sampled in an order that would ensure the 

Middle Rio Grande was flowing at all sites at 

the time of sampling. The reordered sampling 

during low streamflow conditions facilitated the 

assessment of as many sites as possible, as well 

as the measurement of physical properties and 

sampling of fish. Those sites that were at the 

greatest risk of drying were visited in early June 

2012, and those sites that were expected to have 

streamflow throughout the summer were visited 

in August 2012. The period of comparatively 

low streamflows in the summer of 2012 was an 

opportunity to determine available habitat during 

a time of the year when water temperatures in the 

Middle Rio Grande are seasonally high and the 

stream channel is more accessible for sampling, 

thus providing more ideal conditions for the 

evaluation of habitat use by and distribution of 

fishes at low flow.

The approach used to assess mesohabitats in the 

Middle Rio Grande was modified from Parasiewicz 

and Dunbar (2001) (fig. 5). Mesohabitat assessments 

generally consist of (1) geospatial measurements to 

document the sampling site, (2) physical measurements 

of the stream properties, and (3) biological sampling at 

the site. Geospatial measurements (data 

associated with a particular location) 

are made as a first step to generate maps 

over a range of streamflows (that is, how 

the various mesohabitat types change 

under different streamflow conditions) 

(Bovee and others, 1998, 2008). 

Geospatial and physical measurements 

provide a description of the ecohydraulic habitat conditions for the 

streamflow at the time the measurements 

are made. Physical measurements and 

biological measurements are used to 

determine habitat use by selected fish 

species.

For this study, the following 

mesohabitats were mapped at each study 

site when present: riffles, runs, pools 

(channel and eddy), isolated pools, 

forewaters, backwaters, embayments, 

and flats (table 2, fig. 6). Point bars 

and channel bars were also mapped to 

provide a more complete assessment of 

the active channel at each site. Data from 

two types of pools—channel and eddy—

were combined into a “pools” category 

for analysis. 

Digital mapping techniques were 

used for all geospatial measurements. 

The hardware, software, and field 

methods that were used to accomplish 

the study mapping goals were selected 

specifically to overcome the challenges 

of working in a remote, arid riverine 

environment. A geographic information 

system (GIS) (Esri, 2013) and Global 

Positioning System (GPS) were used to 

create the map in the field. Location data 

were collected by using a Trimble DSM 

232 modular receiving unit (Trimble, 

2015a) with an OmniSTAR subscription 

(Trimble, 2015b) for real-time, subfoot 

accuracy observations needed for 

mapping. The GPS observations were 

directly read into a field laptop computer 

for onsite visualization within the GIS, 

and polygons were created by using 

location information, aerial photography, 

and editing tools.

Field mapping was accomplished by using a variety 

of approaches based on streamflow, stream depth, and 

streambank accessibility. Each study reach was visited 

twice (except for Peña Blanca and Bernalillo, which were 

only sampled in winter 2011–12) (table 1), corresponding 

to the periods of moderate and low streamflows identified 

for this study. For the majority of the field mapping, the 

edge of the water throughout a site reach was extracted 

from high-resolution, remotely sensed imagery, which 

was used as a framework for all subsequently mapped 

mesohabitats within a given reach at a site. The field data 

collection process required two individuals working in 

tandem, communicating by 

using a wireless connection 

between the GPS receiver and 

laptop computer. After the edge 

of water was delineated, the 

study reach was subdivided 

into smaller polygons, each 

representing individual 

mesohabitats. Individual 

mesohabitats were created 

by walking boundaries of 

each mesohabitat or through 

photointerpretation in the field. 

Polygons created through 

this process were stored and 

attributed in an ArcGIS 10.0 

personal geodatabase (Esri, 

2013) and stored as Microsoft 

Access (1997–2003) files. 

Collectively, the database 

information and remotely sensed 

imagery made it possible to 

generate a detailed map for each 

study site at each targeted flow. 

Mesohabitat

assessment

Run

Point bar

Channel bar

Channel bar

Example river system

Physical measurement Biological sampling

Geospatial measurement

Mapping

Figure 5. Overview of the approach used to map mesohabitats in the Middle Rio Grande, New Mexico 

(modified from Parasiewicz and Dunbar, 2001). 

Riffle

Backwater

Isolated pool

Forewater

Eddy pool

Channel pool

Run

Embayment

Point bar

Channel

bar

Flat

Run

Run

Run

Riffle

Flat

Run

Margin

Pool

Secondary channel trace

Plan view Profile review

Figure 6. Mapped mesohabitat types identified in the Middle Rio Grande, New Mexico (modified 

from Platania, 1993).
Peña Blanca Sampling Site Bernalillo Sampling Site

November 10, 2011

Number of wetted mapped mesohabitats

70

0 10 20 30 40 50 60

71,327 square meters

N/O

9

70

22

21

57

20

62

61

43

66

39

68

42

18

1

2

9

4

12

37

106 ̊21’30”

35 ̊34’

35 ̊33’40”

106 ̊21’40” 106 ̊21’20”

A

0 50 100 150 200 METERS

0 125 250 375 500 FEET

37,144 square meters

November 11, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

17

N/O

N/O

12

13

10

1

17

5

7

4 3

6

2

15

16

9 8

14

0 50 100 150 200 METERS

0 125 250 375 500 FEET

106 ̊33’30”

35 ̊19’15”

35 ̊19’

35 ̊19’7.5”

35 ̊18’52.5”

106 ̊33’37.5”

B

U.S. Geological Survey hydrologist delineates 

backwaters at Peña Blanca sampling site. 

Photograph by Daniel K. Pearson, U.S. Geological 

Survey, November 10, 2011.

A B

Upper end of Bernalillo sampling site showing submerged 

bar/riffle/run complex (from left to right) in the foreground 

and cut bank in the background. Photograph by Daniel K. 

Pearson, U.S. Geological Survey, November 11, 2011.

Mapped Mesohabitat Features—Continued

 A total of eight different types of wetted mesohabitats 

were mapped across the entire study area: riffles, runs, 

pools, isolated pools, forewaters, backwaters, embayments, 

and flats. The only sampling site that contained all 8 wetted 

mesohabitat types was Abeytas on June 7, 2012, but 10 of 

the 13 sampling sites mapped in summer 2012 contained 

at least 7 of the 8 potential wetted mesohabitat types. In 

contrast, only 3 out of 15 sampling sites (Peña Blanca, La 

Orilla, and Barelas) that were mapped in winter 2011–12 

contained as many as seven different wetted mesohabitat 

types, and all 3 of these sampling sites were located in 

the most upstream part of the study area (3 of the 4 most 

upstream sampling sites). La Joya contained the fewest 

types of wetted mesohabitats in summer 2012 with five, 

whereas Los Lunas I and Rio Salado contained the fewest 

types of wetted mesohabitats in winter 2011–12 with three 

each. The average number of different wetted mesohabitat 

types per site mapped in winter 2011–12 and summer 2012 

were 5.3 and 6.8, respectively. In general, decreases in 

streamflow between winter 2011–12 and summer 2012 led 

to increased complexity in terms of the number of different 

types of wetted mesohabitats that were mapped at each 

sampling site. Barelas was the only sampling site where 

a greater number of wetted mesohabitats was mapped in 

winter 2011–12 compared to summer 2012.

Decreases in streamflow between winter 2011–12 and 

summer 2012 also led to increased complexity in terms of 

the total number of wetted mesohabitats that were mapped 

at each sampling site. More than half of the sampling sites 

that were mapped during winter 2011–12 contained fewer 

than 40 mesohabitats. During summer 2012, more than 40 

mesohabitats were mapped at all of the sites except for the 

Rio Salado site, where 40 mesohabitats were mapped. In 

winter 2011–12, the largest number of wetted mesohabitats 

mapped at a sampling site was 70 at Peña Blanca, and 

the smallest was 16 at Lemitar. In summer 2012, more 

than 100 wetted mesohabitats were mapped at three 

different sampling sites (Barelas, Los Lunas I, and Arroyo 

del Tajo) with Los Lunas I having the most at 145. The 

average number of wetted mesohabitats mapped in winter 

2011–12 was 38.1, whereas the average number of wetted 

mesohabitats mapped in summer 2012 was 84.5. In other 

words, decreases in streamflow between winter 2011–12 

and summer 2012 resulted on average in more than twice as 

many wetted mesohabitats at each sampling site in summer 

2012 relative to winter 2011–12.

In many cases, decreases in streamflow between 

winter 2011–12 and summer 2012 also led to increased 

complexity in terms of the total number of channel bars 

mapped. Channel bars are defined as a transitory parcel 

of land surrounded by water and typically either devoid 

of or containing annual vegetation (table 2). Reductions 

in stage associated with decreased streamflow resulted in 

the emergence of channel bars in areas that were shallow 

wetted mesohabitats, particularly flats and shallow runs, 

under higher streamflow conditions (figs. 8A and 8B show 

an example of this change in channel complexity at the Los 

Lunas I site). The emergence of channel bars contributes to 

the creation of additional wetted mesohabitats and higher 

complexity (particularly along the margins and at the 

downstream end of the channel bars) because of the flowaltering effects caused by the channel bars (figs. 8A and 8B). 

Los Lunas I had the most channel bars (32) of any 

of the reaches in winter 2011–12 and the second most in 

summer 2012 (44), and not surprisingly, it had the second 

most wetted mesohabitats in winter 2011–12 (59) and 

the most in summer 2012 (145). The average and median 

number of channel bars mapped in winter 2011–12 was 

16.0 and 13.0, respectively, whereas the average and 

median number of channel bars mapped in summer 2012 

was 20.5 and 19, respectively. Figure 8C shows the relation 

between the number of channel bars and the number of 

wetted mesohabitats mapped at each of the 15 sampling 

sites on the Middle Rio Grande during winter 2011–12 and 

summer 2012. 

Least-squares linear regression analyses were done 

to assess the relations between the number of wetted 

mesohabitats and the number of channel bars. In leastsquared linear regression analyses, the R-squared (R2

) or 

coefficient of determination is one indicator of the goodness 

of fit, that is, how well the regression equation fits the data 

(Iman and Conover, 1982; Helsel and Hirsch, 2002).

The largest R2 value was 0.89, which was measured at 

each of the three sites that were sampled in February 2012 

(San Pedro, Bosque del Apache I, and Bosque del Apache 

II); the identical R2 values for these three sites were not 

surprising because these three sampling sites are in close 

proximity to one another at the downstream part of the 

study area. There was also a relatively strong correlation 

(R2=0.78) between the number of channel bars and the 

number of wetted mesohabitats for all sites sampled in June 

and August 2012; however, the correlation in sites sampled 

in November and December 2011 was relatively low 

(R2=0.38).

Another factor that can contribute to channel 

complexity is bed-substrate composition. The bed-substrate 

composition of the Peña Blanca and Bernalillo sites was 

dominated by coarse-grained bed materials, particularly 

coarse gravels and cobble in samples collected in winter 

2011–12 (fig. 9). Downstream from these two sampling 

sites, the Rio Grande is characterized by a broader, more 

low-gradient channel dominated by sand. Fine-grained silts 

and clays are more prevalent in the mid-reach sampling 

sites including Los Lunas I and II, Abeytas, La Joya, and 

Rio Salado. The increase in silts and clays at these sampling 

sites could be the result of finer-grained contributions from 

two large tributaries to the Rio Grande, the Rio Puerco and 

Rio Salado, both of which join 

the Rio Grande downstream 

from Albuquerque (fig. 3).

Consistent with the 

preceding discussion, decreases 

in streamflow typically led to 

increases in channel complexity 

in terms of the number of 

different wetted mesohabitat 

types present, total number 

of mesohabitats present, and 

the number of channel bars. 

Decreases in streamflow 

also led to reductions in 

wetted area for all sampling 

sites mapped in both winter 

2011–12 and summer 2012. 

A graphical representation 

of discharge measured at or 

near each sampling site as it 

relates to channel complexity 

(represented by the number of 

wetted mesohabitats mapped) is 

shown in figure 10. In general, 

sampling sites that were mapped 

at higher discharge during 

winter 2011–12 resulted in 

the lowest number of wetted 

mesohabitats mapped, whereas 

sampling sites mapped at 

lower discharge in summer 

2012 resulted in the highest 

number of wetted mesohabitats. Lower discharge rates 

result in increased mesohabitat fragmentation, increased 

numbers of slack water mesohabitats (isolated pools, 

backwaters, forewaters, and embayments), smaller (area) 

mesohabitats, greater numbers of mesohabitats, and a 

more braided stream channel. For higher discharge rates, 

smaller mesohabitats are flooded, and the stream channel 

is simplified overall, resulting in fewer slack water 

mesohabitats, larger (area) mesohabitats, and a stream 

channel that is less braided. Based on field experience, it is 

expected that during high magnitude discharge conditions 

when the channel is bankfull, each reach should consist of 

no more than a few mesohabitats.

Maps showing the mesohabitats for each of the 15 

sites are presented in sheets 3–7. Maps are arranged 

from upstream to downstream order and grouped by 

MRGBI reach name. Numbered mesohabitats labeled 

in yellow correspond to the subset of mesohabitats 

where Rio Grande silvery minnows were caught. 

Numbered mesohabitats outlined in black on maps 

correspond to the subset of mesohabitats where physical 

habitat measurements (and water-quality properties 

were measured in summer 2012) and fish collection were 

attempted. In addition, graphs showing mesohabitat 

characteristics and selected photographs of field 

activities and site conditions are shown for each site.

Number of wetted mesohabitat types

0

1

2

3

4

5

6

7

8

9

Wetted area, in square meters

Number of wetted mesohabitats Number of channel bars

November and December 2011 February 2012 June and August 2012

Sampling period

EXPLANATION

U.S. Geological Survey sampling sites

A.

B.

C.

D.

160

140

120

100

80

60

40

20

0

50

45

40

35

30

25

20

15

10

5

0

120,000

100,000

80,000

60,000

40,000

20,000

0

PNB BRN LOR BAR PAD LL1 LL2 ABY LJY RSL LEM ATJ SPD BA1 BA2

Figure 7. Number of A, wetted mesohabitat types mapped; B, wetted 

mesohabitats mapped; C, channel bars mapped; and D, wetted area at 15 

sampling sites on the Middle Rio Grande, winter 2011–12 and summer 2012.

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50

Number of channel bars

Number of wetted mesohabitats

November and December 2011

February 2012

June and August 2012

 

Sampling periods

EXPLANATION

A.

B.

C.

Least-squares linear regression lines

November and December 2011

February 2012

June and August 2012

R2=0.78

R2

=0.38

R2

=0.89

Note: R2 is coefficient of determination

Figure 8. Comparison of differences in channel complexity at the Los Lunas I site during A, November 12, 2011, and B, June 5, 

2012, following a reduction in stage; C, correlation between the number of channel bars and the number of wetted mesohabitats 

mapped at each site during winter 2011–11 and summer 2012.

Hardpan

Boulder (greater than 256)

Cobble (greater than 64 and less than or equal to 256)

Coarse gravel (greater than 12 and less than or equal to 64)

Fine gravel (greater than 4 and less than or equal to 12)

Sand (greater than 0.0625 and less than or equal to 2)

Silt and clay (less than or equal to 0.0625)

Substrate categories (size in millimeters)—

EXPLANATION

Area-weighted substrate composition, in percent

A. Winter 2011–12

U.S. Geological Survey sampling sites

0

B. Summer 2012 Not Sampled Not Sampled

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

PNB BRN LOR BAR PAD LL1 LL2 ABY LJY RSL LEM ATJ SPD BA1 BA2

U.S. Geological Survey sampling sites

PNB BRN LOR BAR PAD LL1 LL2 ABY LJY RSL LEM ATJ SPD BA1 BA2

Figure 9. Area-weighted substrate composition at 15 sampling sites on the Middle Rio Grande, A, winter 2011–12; and B, summer 2012.

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200

Discharge, in cubic feet per second

Number of wetted mesohabitats mapped

PNB

BRN

LOR

BAR*

PAD

LL1

LL2* ABY

LJY

RSL

LEM

ATJ

SPD

BA1

BA2*

LOR

BAR*

PAD

LL1

LL2

ABY

LJY

RSL

LEM

ATJ

SPD*

BA1

BA2

SPD

BA2

NOTE: Discharge was not measured in the field at locations indicated with *; plotted discharge in these cases is the daily mean discharge one day after the site was mapped

for the nearest U.S. Geological Survey streamflow-gaging station upstream from the site.

November and December 2011

February 2012

June and August 2012

Sampling periods

EXPLANATION

Figure 10. Graphical representation of discharge as it relates to channel complexity (represented by the number of wetted 

mesohabitats mapped).

86,252 square meters

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O

November 16, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

40

N/O 104,256 square meters 86,252 square meters

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O

November 16, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

40

N/O 104,256 square meters

C

Looking upstream from western edge of channel bar 

towards the bottom end of the large channel bar that 

occupies mid-channel at the top of the La Orilla reach. 

Photograph by Daniel K. Pearson, U.S. Geological Survey, 

August 13, 2012.

34

28

38

1

30

4

16

40

5

14

22

20

8 15

0 50 100 150 200 METERS

0 125 250 375 500 FEET

35 ̊9’30”

35 ̊9’15“

35 ̊9’

106 ̊40’30” 106 ̊40’15”

2*

*Habitat parameters were not measured at 

this location, but fish collection was attempted.

35 ̊9’30”

35 ̊9’15”

35 ̊9’

87

48

64

70

5

68

3

53

86

82

89

80

84

4

8

81

10

74

19

48

49

51

17

50

13

36

33

12

45

25

46

106 ̊40’30” 106 ̊40’15”

C

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Winter 2011–12

November 10, 2011

Winter 2011–12

November 16, 2011

Summer 2012

August 11, 2012

Winter 2011–12

November 11, 2011

La Orilla Sampling Site

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

ABBREVIATIONS and EXPLANATION

pools

riffles

forewaters

backwaters

flats

isolated pools

channel bar*

point bar*

*Not included in wetted mesohabitat area 

donut graphs or bar graphs showing 

number of wetted mesohabitats mapped

flat

riffle

run

pool

isolated pool

backwater

forewater

embayment

runs

Base from Middle Rio Grande Conservation District,

March–May 2012, 0.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base from Bureau of Reclamation,

February 2012, 1.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base credit in maps for Peña Blanca, Bernalillo, La Orilla,

Barelas, Los Padillas, Los Lunas I, and Los Lunas II (sheets 3 and 4) 

Base credit in maps for Abeytas, La Joya, Rio Salado, Lemitar, Arroyo del Tajo, San Pedro,

Bosque del Apache I, and Bosque del Apache II (sheets 5, 6, and 7)

U.S. Geological Survey sampling

sites short names and map identifier

Peña Blanca, PNB

Bernalillo, BRN

La Orilla, LOR

Barelas, BAR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

45,744 square meters**

Wetted mesohabitat area

NOTE: Mesohabitat area donut plots are scaled relative to one another as a function of area.

NOTE: Numbered mesohabitats labeled in yellow correspond to the subset of mesohabitats where Rio Grande silvery minnows were caught.

NOTE: Numbered mesohabitats that are outlined in black on maps correspond to the subset of mesohabitats where physical habitat measurements

 (and water-quality properties were measured in summer 2012) and fish collection was attempted. 

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O (not observed)

Total number

of wetted 

mesohabitats 

mapped

Date site was mapped

**Total areal extent of wetted

mesohabitat mapped 

Photo identifier and direction facing when

photograph was taken

A

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 3 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.
U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 4 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service

Los Lunas II Sampling Site

Los Lunas I Sampling Site

2

4

37

31

3

9

5

46

32

41

11

19

24

15

6

34 ̊45’15”

106 ̊44’30”

34 ̊45’

106 ̊44’15”

E

0 50 100 150 200 METERS

0 125 250 375 500 FEET

97,840 square meters

November 14, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

50

N/O

N/O

N/O

66,331 square meters

June 6, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

89

N/O 97,840 square meters

November 14, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

50

N/O

N/O

N/O

66,331 square meters

June 6, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

89

N/O

102,784 square meters

November 12, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

59

N/O

N/O

N/O

N/O

N/O

0 10 20 

Number of w

N/O

73,866 square meters 102,784 square meters

November 12, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

59

N/O

N/O

N/O

N/O

N/O

June 5, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

145

N/O

D

Looking downstream from a channel bar near 

the upstream end of the Los Lunas I sampling 

site. Photograph by Daniel K. Pearson,

U.S. Geological Survey, June 5, 2012.

E

Looking downstream towards narrow run between two channel 

bars; U.S. Geological Survey geographer processing mapped 

data in the foreground. Photograph by Christopher L. Braun, U.S. 

Geological Survey, November 14, 2011.

F

Looking upstream from a run near mid-reach at Los Lunas II 

sampling site. Photograph by Daniel K. Pearson, U.S. Geological 

Survey, June 6, 2012.

Winter 2011–12

November 14, 2011

34 ̊45’15”

34 ̊45’

48

1

80

85

72

40

60

13

90

70

84

86

49

82

50

57

73

25 10

28

68 64

88

54

21

53

30

106 ̊44’30” 106 ̊44’15”

F

0 50 100 150 200 METERS

0 125 250 375 500 FEET

62*

*Habitat parameters were not measured at 

this location, but fish collection was attempted.

Summer 2012

June 6, 2012

Barelas Sampling Site

Los Padillas Sampling Site

November 9, 2011 August 10, 2012

0 10 20 30 40 50 60 0 10 20 30 40 50 60

Number of wetted mapped mesohabitats Number of wetted mapped mesohabitats

35 114

N/O

N/O

113,199 square meters N/O 103,094 square meters

November 9, 2011 August 10, 2012

0 10 20 30 40 50 60 0 10 20 30 40 50 60

Number of wetted mapped mesohabitats Number of wetted mapped mesohabitats

35 114

N/O

N/O

113,199 square meters N/O 103,094 square meters

35 ̊4’45”

35 ̊4’30”

112

29

47

54

3

63

48

42

59

99

18

20

55

54

106 ̊40’30” 106 ̊40’15”

112

29

39

80

103

76

83

74

31

84

92

89

36

33

72

109

42

0 50 100 150 200 METERS

0 125 250 375 500 FEET

89,210 square meters

November 15, 2011

Number of wetted mapped mesohabitats

52

0 10 20 30 40 50 60

N/O

N/O

N/O

67,327 square meters

August 9, 2012

Number of wetted mapped mesohabitats

57

0 10 20 30 40 50 60

N/O

89,210 square meters

November 15, 2011

Number of wetted mapped mesohabitats

52

0 10 20 30 40 50 60

N/O

N/O

N/O

67,327 square meters

August 9, 2012

Number of wetted mapped mesohabitats

57

0 10 20 30 40 50 60

N/O

Oblique aerial photograph showing lower half of Los Padillas sampling site with approximate extents of readily identifiable 

mesohabitats delineated. Photograph by Daniel K. Pearson, U.S. Geological Survey, June 4, 2012.

run

point bar

channel bar

channel bar

5

14

32

24

15

16

2

4

26

29

19

9

23

27

20

8

35

7

106 ̊40’15”

35 ̊4’45”

35 ̊4’30”

106 ̊40’30”

A B

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Oblique aerial photograph showing downstream 

end of Los Padillas sampling site with 

approximate extents of readily identifiable 

mesohabitats delineated. Delineated 

mesohabitats do not correspond to mapped 

mesohabitats from either November 15, 2011, 

or August 9, 2012. Photograph by Daniel K. 

Pearson, U.S. Geological Survey, June 4, 2012.

Looking downstream along secondary channel at Los Padillas 

sampling site. Photograph by Daniel K. Pearson, U.S. Geological 

Survey, November 15, 2011.

C

U.S. Geological Survey hydrologist delineates a channel bar using GPS at the 

Barelas sampling site. Photograph by Daniel K. Pearson, U.S. Geological Survey, 

November 9, 2011.

A B

Downstream end of Barelas sampling site. Photograph by Daniel K. Pearson,

U.S. Geological Survey, November 9, 2011.

Winter 2011–12

November 9, 2011

3

1

47

8

20

18

17

23

13

52

6

44 45

14

5

3 35

39

37 36

29

34 ̊58’

34 ̊57’45”

34 ̊57’30”

106 ̊41’22.5” 106 ̊41’15” 106 ̊41’7.5”

C

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Winter 2011–12

November 15, 2011

1

23

7

10

59

31

30

35

13

21

22

32

46

25

37

40

8

16 17

34 ̊2’30”

34 ̊2’15”

106 ̊42’52.5” 106 ̊42’45” 106 ̊42’37.5”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Winter 2011–12

November 12, 2011

Summer 2012

August 10, 2012

34 ̊58'

34 ̊57’45”

34 ̊57’30”

6

26

1

3

20

21

5

15

17

7

11

10

27

6

26

20

21

40

1 5

1 7

47

57

49

38

53

39

1 1

1 0

48

37

27

52

30

31

46

35

55

51

0 50 100 150 200 METERS

0 125 250 375 500 FEET

106 ̊41’22.5” 106 ̊41’15” 106 ̊41’7.5”

Summer 2012

August 9, 2012

34 ̊2’30”

34 ̊2’15”

2

95

88

216

61

171

134

45

36

93

40

69

209

144

211

213

58

234

53

9

23

163

159

16

164

162

19

17 39

161

0 50 100 150 200 METERS

0 125 250 375 500 FEET

106 ̊42’52.5” 106 ̊42’45” 106 ̊42’37.5”

D

Summer 2012

June 5, 2012

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

ABBREVIATIONS and EXPLANATION

pools

riffles

forewaters

backwaters

flats

isolated pools

channel bar*

point bar*

*Not included in wetted mesohabitat area 

donut graphs or bar graphs showing 

number of wetted mesohabitats mapped

flat

riffle

run

pool

isolated pool

backwater

forewater

embayment

runs

Base from Middle Rio Grande Conservation District,

March–May 2012, 0.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base from Bureau of Reclamation,

February 2012, 1.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base credit in maps for Peña Blanca, Bernalillo, La Orilla,

Barelas, Los Padillas, Los Lunas I, and Los Lunas II (sheets 3 and 4) 

Base credit in maps for Abeytas, La Joya, Rio Salado, Lemitar, Arroyo del Tajo, San Pedro,

Bosque del Apache I, and Bosque del Apache II (sheets 5, 6, and 7)

U.S. Geological Survey sampling

sites short names and map identifier

Peña Blanca, PNB

Bernalillo, BRN

La Orilla, LOR

Barelas, BAR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

45,744 square meters**

Wetted mesohabitat area

NOTE: Mesohabitat area donut plots are scaled relative to one another as a function of area.

NOTE: Numbered mesohabitats labeled in yellow correspond to the subset of mesohabitats where Rio Grande silvery minnows were caught.

NOTE: Numbered mesohabitats that are outlined in black on maps correspond to the subset of mesohabitats where physical habitat measurements

 (and water-quality properties were measured in summer 2012) and fish collection was attempted. 

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O (not observed)

Total number

of wetted 

mesohabitats 

mapped

Date site was mapped

**Total areal extent of wetted

mesohabitat mapped 

Photo identifier and direction facing when

photograph was taken

A

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.
U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 5 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service

Lemitar Sampling Site

13,547 square meters

August 6, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

68

N/O

64,555 square meters

December 1, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

16

N/O

N/O

N/O

N/O

F

A

Measuring depths and velocities in a 

run (mesohabitat ID 10). Photograph 

by Daniel K. Pearson, U.S. Geological 

Survey, December 2, 2011.

Facing northward from the Chaparral 

Loop Bridge approximately 4.6 miles 

downstream from the Lemitar site. 

Photograph by Daniel K. Pearson, U.S. 

Geological Survey, August 6, 2012.

3

9

8

7

2 1

6

16

10

4

12

5

14

11

34 ̊11’15”

106 ̊53’7.5” 106 ̊53’ 106 ̊52’52.5”

34 ̊11’

34 ̊10’45”

F

0 50 100 150 200 METERS

0 125 250 375 500 FEET

*Habitat parameters were not measured at 

this location, but fish were collected.

15*

1

57

42

16

54

8

35

4

62

9

3

48

29

36

52

44

18

25

45

21

5

68

14

41

66

67

23

106 ̊53’7.5” 106 ̊53’ 106 ̊52’52.5”

34 ̊11’15”

34 ̊11’

34 ̊10’45”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Abeytas Sampling Site

106,058 square meters

November 28, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

49

N/O

N/O

45,744 square meters

June 7, 2012

10 20 30 40 50 60

Number of wetted mapped mesohabitats

61

0

Looking west toward a burn-scarred area from a submerged channel bar in the upstream end of the 

Abeytas sampling site. U.S. Geological Survey personnel delineating mesohabitats and editing the 

map product output. Photograph by Michael D. Porter, U.S. Army Corps of Engineers, June 7, 2012.

38

14

36

10

8

29

2

20

48

41

22

9

25

44

28

15

23

11

106 ̊48'15" 106 ̊48'

0 50 100 150 200 METERS

0 125 250 375 500 FEET

34 ̊27'15"

34 ̊27'

34 ̊26'45"

25

2

3

28

51

56

32

38

52

41

6

34

42

8

9

25

21

24

10

16

53

23

17

12

22

11

20

19

14

106 ̊48'

34 ̊27'15"

34 ̊27'

34 ̊26'45"

106 ̊48'15"

A

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Winter 2011–12

November 28, 2011

Winter 2011–12

December 1, 2011

Summer 2012

June 7, 2012

Summer 2012

August 6, 2012

La Joya Sampling Site

5

9

15

8

10

14 11

17

18

6

12

3

4

16

34 ̊19’15”

106 ̊51’15”

34 ̊19’

34 ̊18’45”

106 ̊51’22.5” 106 ̊51’7.5”

B

0 40 80 120 160 METERS

0 100 200 300 400 FEET

1

9

39

31

60

45 55

57

26

19

22

51

47

11

23

36

17

24

7

12

62

54

68

30

10

70

0 40 80 120 160 METERS

0 100 200 300 400 FEET

106 ̊51’22.5“ 106 ̊51’15“ 106 ̊51’7.5“

34 ̊19’15“

34 ̊19’

34 ̊18’45”

C

55,712 square meters

November 29, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

18

N/O

N/O

N/O

24,921 square meters

August 8, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

70

N/O

N/O

N/O

Looking southwest at isolated pool near 

the upstream end of the La Joya sampling 

site. Photograph by Daniel K. Pearson, U.S. 

Geological Survey, November 29, 2011.

Looking west toward an isolated pool that U.S. Geological 

Survey hydrologist is delineating in the upper half of the La 

Joya sampling site. Photograph by Daniel K. Pearson, U.S. 

Geological Survey, August 8, 2012.

Winter 2011–12

November 29, 2011

Summer 2012

August 8, 2012

Rio Salado Sampling Site

56,374 square meters

November 30, 2011

Number of wetted mapped mesohabitats

24

0 10 20 30 40 50 60

N/O

N/O

N/O

N/O

N/O

27,088 square meters

August 7, 2012

Number of wetted mapped mesohabitats

40

0 10 20 30 40 50 60

N/O

N/O

Looking southwest toward point bar with 

loose livestock in the Rio Salado sampling 

site. Photograph by Daniel K. Pearson, U.S. 

Geological Survey, November 30, 2011.

Looking northwest toward the downstream end 

of the Rio Salado sampling site. Suspended 

sediment (visible in the run shown in the 

foreground) is caused by reduced channel 

velocity associated with local hydraulics 

caused by San Acacia Diversion Dam. 

Photograph by Daniel K. Pearson, U.S. 

Geological Survey, August 7, 2012.

23

24

8

7 5

9

4

2

34 ̊15’45”

34 ̊15’30”

22

11

10

21 17

20

16

19

18

0 50 100 150 200 METERS

0 125 250 375 500 FEET

*Habitat parameters were not measured at 

this location, but fish collection was attempted.

106 ̊52’ 106 ̊51’45”

D

12*

Winter 2011–12

November 30, 2011

28

4

23

1

9

2

5

29

27

15

35

25

10 38

13

26

12

33

24

34 ̊15’45”

34 ̊15’30”

E

0 50 100 150 200 METERS

0 125 250 375 500 FEET

106 ̊52’ 106 ̊51’45”

Summer 2012

August 7, 2012

B

D

E

C

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

ABBREVIATIONS and EXPLANATION

pools

riffles

forewaters

backwaters

flats

isolated pools

channel bar*

point bar*

*Not included in wetted mesohabitat area 

donut graphs or bar graphs showing 

number of wetted mesohabitats mapped

flat

riffle

run

pool

isolated pool

backwater

forewater

embayment

runs

Base from Middle Rio Grande Conservation District,

March–May 2012, 0.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base from Bureau of Reclamation,

February 2012, 1.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base credit in maps for Peña Blanca, Bernalillo, La Orilla,

Barelas, Los Padillas, Los Lunas I, and Los Lunas II (sheets 3 and 4) 

Base credit in maps for Abeytas, La Joya, Rio Salado, Lemitar, Arroyo del Tajo, San Pedro,

Bosque del Apache I, and Bosque del Apache II (sheets 5, 6, and 7)

U.S. Geological Survey sampling

sites short names and map identifier

Peña Blanca, PNB

Bernalillo, BRN

La Orilla, LOR

Barelas, BAR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

45,744 square meters**

Wetted mesohabitat area

NOTE: Mesohabitat area donut plots are scaled relative to one another as a function of area.

NOTE: Numbered mesohabitats labeled in yellow correspond to the subset of mesohabitats where Rio Grande silvery minnows were caught.

NOTE: Numbered mesohabitats that are outlined in black on maps correspond to the subset of mesohabitats where physical habitat measurements

 (and water-quality properties were measured in summer 2012) and fish collection was attempted. 

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O (not observed)

Total number

of wetted 

mesohabitats 

mapped

Date site was mapped

**Total areal extent of wetted

mesohabitat mapped 

Photo identifier and direction facing when

photograph was taken

A

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.
62,763 square meters

February 7, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

33

June 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O

N/O N/O

29,176 square meters

Bosque del Apache I Sampling Site

29

33

9

24

4

13

10

22

26

18

14

5

23

30

28

21

19

12

29

33

24

4

10

5

30

12

9

13

22

26

24

18

14

23

28

21

19

16

17

33 ̊53’

106 ̊50’45”

33 ̊52’45”

106 ̊51’

33 ̊52’30”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

1

55

16

39

17

53

81

38

2

22

32

42

36

73

28

26

49

67

37

7

31

91

12

19

89

93

92

82

20

106 ̊51’ 106 ̊50’45”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Delineation of secondary channel within point bar. Location where photo was taken is not shown 

on map because the mapping effort at the Bosque del Apache I sampling site on December 7, 2011, 

could not be completed because snow and ice made determination and delineation of mesohabitat 

types problematic. Photograph by Daniel K. Pearson, U.S. Geological Survey, December 7, 2011. 

Water being transferred from the conveyance channel to the main channel of the Rio Grande 

approximately 700 feet downstream from the Bosque del Apache I site. Photograph by Daniel K. Pearson, 

U.S. Geological Survey. 

Looking southwest toward the upstream boundary of the Bosque del Apache I 

sampling site. Photograph taken by Daniel K. Pearson, U.S. Geological Survey, on 

September 28, 2011, when river bed was nearly dry and diversions for agriculture 

were still taking place.

Winter 2011–12

February 7, 2012

Summer 2012

June 11, 2012

Arroyo del Tajo Sampling Site

34 ̊2’45”

34 ̊2’30”

34 ̊2’15”

16

5

11

23

42

44

17

29

47

38

32

31

14

13

35

30

19

21

106 ̊52’ 106 ̊51’45”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

18*

46*

*Habitat parameters were not measured

at these locations, but fish collection

was attempted.

13

12

7

23

31

22

49

30 44

4

48

28

39

33

47

37

104

101

79

65

58

67

53

70

57

68

69

80

55

54

107

106 ̊52’ 106 ̊51’45”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

Winter 2011–12

December 1, 2011

Summer 2012

June 8, 2012

Seining by U.S. Fish and Wildlife personnel at unknown location within the Arroyo del Tajo 

sampling site. Photograph by U.S. Geological Survey on June 9, 2012.

80,015 square meters

December 1, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

50

N/O

N/O

N/O

49,697 square meters

June 8, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

109

N/O

San Pedro Sampling Site

1

51

27

20

67

61

47

31

25

3

82

55

58

74

81

66

60

71

59

46

12

50

76

36

86

63

54

73

106 ̊51’15” 106 ̊51’

A

40*

0 50 100 150 200 METERS

0 125 250 375 500 FEET

*Habitat parameters were not measured at 

this location, but fish were collected.

7

2 5

6

4

3

8

18

12

11

9

17

10

16

33 ̊54’30”

106 ̊51’15” 106 ̊51’

33 ̊54’15”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

1

14

18

15

13

17

9

16

11

12

10

20

19

1

7

8

5

2

6

4

3

106 ̊51’15” 106 ̊51’

0 50 100 150 200 METERS

0 125 250 375 500 FEET

33 ̊54’30”

33 ̊54’15”

43,435 square meters

December 3, 2011

Number of wetted mapped mesohabitats

25

0 10 20 30 40 50 60

N/O

N/O

42,345 square meters

February 6, 2012

Number of wetted mapped mesohabitats

20

0 10 20 30 40 50 60

N/O

N/O

N/O

30,313 square meters

June 9, 2012

Number of wetted mapped mesohabitats

84

0 10 20 30 40 50 60

N/O

Winter 2011–12

December 3, 2011

Winter 2011–12

February 6, 2012

Summer 2012

June 9, 2012

Pumps transferring water from the conveyance channel to the main channel of the Rio Grande 

near San Pedro; the photograph was taken outside the mapped area shown. Photograph by 

Daniel K. Pearson, U.S. Geological Survey, June 9, 2012.

A

Facing downstream at midchannel and approximately mid-reach in the San Pedro sampling site. 

Photograph by Daniel K. Pearson, U.S. Geological Survey, June 9, 2012. 

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

ABBREVIATIONS and EXPLANATION

pools

riffles

forewaters

backwaters

flats

isolated pools

channel bar*

point bar*

*Not included in wetted mesohabitat area 

donut graphs or bar graphs showing 

number of wetted mesohabitats mapped

flat

riffle

run

pool

isolated pool

backwater

forewater

embayment

runs

Base from Middle Rio Grande Conservation District,

March–May 2012, 0.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base from Bureau of Reclamation,

February 2012, 1.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base credit in maps for Peña Blanca, Bernalillo, La Orilla,

Barelas, Los Padillas, Los Lunas I, and Los Lunas II (sheets 3 and 4) 

Base credit in maps for Abeytas, La Joya, Rio Salado, Lemitar, Arroyo del Tajo, San Pedro,

Bosque del Apache I, and Bosque del Apache II (sheets 5, 6, and 7)

U.S. Geological Survey sampling

sites short names and map identifier

Peña Blanca, PNB

Bernalillo, BRN

La Orilla, LOR

Barelas, BAR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

45,744 square meters**

Wetted mesohabitat area

NOTE: Mesohabitat area donut plots are scaled relative to one another as a function of area.

NOTE: Numbered mesohabitats labeled in yellow correspond to the subset of mesohabitats where Rio Grande silvery minnows were caught.

NOTE: Numbered mesohabitats that are outlined in black on maps correspond to the subset of mesohabitats where physical habitat measurements

 (and water-quality properties were measured in summer 2012) and fish collection was attempted. 

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O (not observed)

Total number

of wetted 

mesohabitats 

mapped

Date site was mapped

**Total areal extent of wetted

mesohabitat mapped 

Photo identifier and direction facing when

photograph was taken

A

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 6 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service
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composition, and mesohabitat use of the Rio Grande silvery minnow over a range of 

seasonal flow regimes in the Rio Grande/Rio Bravo del Norte, in and near Big Bend 

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Bosque del Apache II Sampling Site

0 50 100 150 200 METERS

0 125 250 375 500 FEET

33 ̊49’

33 ̊48’45”

106 ̊51’22.5” 106 ̊51’15”

33 ̊48’52.5”

33 ̊48’37.5” 59

11

41

36

18

37

63

69

33

28

20

47

55 76

21

13

48

16

27

61

65

38

44

49

30

58

39

4

54

72

106 ̊51’22.5” 106 ̊51’15”

A

0 50 100 150 200 METERS

0 125 250 375 500 FEET

33 ̊49’

33 ̊48’45”

33 ̊48’52.5”

33 ̊48’37.5”

7

3

13

14

11

15

12

6

8

17

16

38

21

19

35

20

22

27

33 28

34

37

33 ̊49’

33 ̊48’45”

106 ̊51’22.5” 106 ̊51’15”

33 ̊48’52.5”

33 ̊48’37.5”

0 50 100 150 200 METERS

0 125 250 375 500 FEET

A

Delineation of left bank looking 

upstream in the Bosque del Apache 

II sampling site. Photograph by 

Daniel K. Pearson, U.S. Geological 

Survey.

Winter 2011–12

December 6, 2011

Winter 2011–12

February 8, 2012

Summer 2012

June 12, 2012

57,050 square meters

February 8, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

39

N/O

N/O

28,625 square meters

June 12, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

76

N/O

56,215 square meters

December 6, 2011

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

55

N/O

N/O

Fish Assemblage Composition and Mapped Mesohabitat Features Over a Range of Streamflows

in the Middle Rio Grande, New Mexico, Winter 2011–12, Summer 2012

By

Daniel K. Pearson, Christopher L. Braun, and J. Bruce Moring

2015 Printed on recycled paper

ISBN 978-1-4113-4010-7

9 7 8141 1 3401 0 7

ISSN 2329-1311 (print)

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3350

ABBREVIATIONS and EXPLANATION

pools

riffles

forewaters

backwaters

flats

isolated pools

channel bar*

point bar*

*Not included in wetted mesohabitat area 

donut graphs or bar graphs showing 

number of wetted mesohabitats mapped

flat

riffle

run

pool

isolated pool

backwater

forewater

embayment

runs

Base from Middle Rio Grande Conservation District,

March–May 2012, 0.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base from Bureau of Reclamation,

February 2012, 1.5-foot resolution compressed mosaic,

New Mexico State Plane Central Zone,

North American Datum of 1983

Base credit in maps for Peña Blanca, Bernalillo, La Orilla,

Barelas, Los Padillas, Los Lunas I, and Los Lunas II (sheets 3 and 4) 

Base credit in maps for Abeytas, La Joya, Rio Salado, Lemitar, Arroyo del Tajo, San Pedro,

Bosque del Apache I, and Bosque del Apache II (sheets 5, 6, and 7)

U.S. Geological Survey sampling

sites short names and map identifier

Peña Blanca, PNB

Bernalillo, BRN

La Orilla, LOR

Barelas, BAR

Los Padillas, PAD

Los Lunas I, LL1

Los Lunas II, LL2

Abeytas, ABY

La Joya, LJY

Rio Salado, RSL

Lemitar, LEM

Arroyo del Tajo, ATJ

San Pedro, SPD

Bosque del Apache I, BA1

Bosque del Apache II, BA2

45,744 square meters**

Wetted mesohabitat area

NOTE: Mesohabitat area donut plots are scaled relative to one another as a function of area.

NOTE: Numbered mesohabitats labeled in yellow correspond to the subset of mesohabitats where Rio Grande silvery minnows were caught.

NOTE: Numbered mesohabitats that are outlined in black on maps correspond to the subset of mesohabitats where physical habitat measurements

 (and water-quality properties were measured in summer 2012) and fish collection was attempted. 

August 11, 2012

0 10 20 30 40 50 60

Number of wetted mapped mesohabitats

93

N/O (not observed)

Total number

of wetted 

mesohabitats 

mapped

Date site was mapped

**Total areal extent of wetted

mesohabitat mapped 

Photo identifier and direction facing when

photograph was taken

A

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/sim3350

Suggested citation: Pearson, D.K., Braun, C.L., and Moring, J.B., 2015, Fish assemblage 

composition and mapped mesohabitat features over a range of streamflows in the Middle 

Rio Grande, New Mexico, winter 2011–12, summer 2012: U.S. Geological Survey Scientific 

Investigations Map 3350, 7 sheets, http://dx.doi.org/10.3133/sim3350.

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3350

Sheet 7 of 7

Prepared in cooperation with the

U.S. Army Corps of Engineers, Albuquerque District, and the U.S. Fish and Wildlife Service