U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5217

Prepared in cooperation with the U.S. Fish and Wildlife Service

Abundance of Host Fish and Frequency of

Glochidial Parasitism in Fish Assessed in Field and 

Laboratory Settings and Frequency of Juvenile Mussels

or Glochidia Recovered from Hatchery-Held Fish,

Central and Southeastern Texas, 2012–13
Cover.

Diagram showing the life cycle of unionid mussels native to Texas (illustration by L.S. Coplin, U.S. Geological Survey).
Abundance of Host Fish and Frequency of 

Glochidial Parasitism in Fish Assessed in 

Field and Laboratory Settings and Frequency 

of Juvenile Mussels or Glochidia Recovered 

from Hatchery-Held Fish, Central and 

Southeastern Texas, 2012–13

By Christopher L. Braun, Charrish L. Stevens, Patricia D. Echo-Hawk,

Nathan A. Johnson, and James B. Moring

Prepared in cooperation with the U.S. Fish and Wildlife Service

Scientific Investigations Report 2014–5217

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Braun, C.L., Stevens, C.L., Echo-Hawk, P.D., Johnson, N.A., and Moring, J.B., 2014, Abundance of host fish and 

frequency of glochidial parasitism in fish assessed in field and laboratory settings and frequency of juvenile mussels 

or glochidia recovered from hatchery-held fish, central and southeastern Texas, 2012–13: U.S. Geological Survey 

Scientific Investigations Report 2014–5217, 53 p., http://dx.doi.org/10.3133/sir20145217.

ISSN (print) 2328-031X

ISSN (online) 2328-0328

ISBN 978-1-4113-3870-8
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Background Information .....................................................................................................................4

Historical Range and Recent (2011) Occurrence of Target Mussel Species..............................7

Purpose and Scope ..............................................................................................................................7

Methods of Investigation .............................................................................................................................7

Site Selection and Reconnaissance .................................................................................................7

Mussel Surveys...................................................................................................................................13

Fish Collection and Field Processing...............................................................................................13

Glochidia Recovery at U.S. Geological Survey Laboratory .........................................................16

Juvenile Mussel and Glochidia Recovery at the U.S. Fish and Wildlife Service

Hatchery..................................................................................................................................16

Quality Assurance...............................................................................................................................17

Abundance of Host Fish..............................................................................................................................17

Frequency of Parasitism in Fish Assessed for Glochidia in Field and Laboratory Settings ............27

Frequency of Juvenile Mussels or Glochidia Recovered from Hatchery-Held Fish ........................45

Summary........................................................................................................................................................50

References....................................................................................................................................................51

Figures

1. Map showing location of sites sampled for fish and mussels in

selected streams as part of a mussel host-fish study, central and

southeastern Texas, 2012–13......................................................................................................3

2. Diagram showing life cycle of unionid mussels native to Texas ..........................................6

3. Map showing historical range for the Texas fatmucket and counties

of known recent (2011) occurrence as part of a mussel host-fish study,

central and southeastern Texas.................................................................................................8

4. Map showing historical range for the golden orb and counties of known

recent (2011) occurrence as part of a mussel host-fish study, central and

southeastern Texas ......................................................................................................................9

5. Map showing historical range for the smooth pimpleback and counties

of known recent (2011) occurrence as part of a mussel host-fish study, central

and southeastern Texas.............................................................................................................10

6. Map showing historical range for the Texas pimpleback and counties

of known recent (2011) occurrence as part of a mussel host-fish study,

central and southeastern Texas...............................................................................................11

7. Map showing historical range for the Texas fawnsfoot and counties of

known recent (2011) occurrence as part of a mussel host-fish study, central

and southeastern Texas.............................................................................................................12

8. Bar graph showing abundance of potential host fish from sites

sampled in 2012 as part of a mussel host-fish study, central and

southeastern Texas, 2012–13....................................................................................................18
iv

9. Bar graph showing abundance of potential host fish from sites sampled

in 2013 as part of a mussel host-fish study, in central and southeastern

Texas, 2012–13.............................................................................................................................28

10. Pie diagram and graphs showing A, percentage, and B, number of

parasitized fish that were assessed in the field or laboratory for glochidia

at 10 sites in 2012 as part of a mussel host-fish study, central and

southeastern Texas, 2012–13....................................................................................................30

11. Pie diagrams and graphs showing A, percentage; B, number; and

C, total length of fish grouped by family that were assessed in the field

or laboratory for glochidia in 2012 as part of a mussel host-fish study,

central and southeastern Texas, 2012–13 ..............................................................................31

12. Pie diagram and graph showing A, percentage, and B, number of

parasitized fish that were assessed in the field or laboratory for glochidia

at nine sites in 2013 as part of a mussel host-fish study, central and

southeastern Texas, 2012–13....................................................................................................32

13. Pie diagram and graphs showing A, percentage; B, number; and

C, average total length of fish grouped by family that were assessed in

the field or laboratory for glochidia in 2013 as part of a mussel host-fish

study, central and southeastern Texas, 2012–13...................................................................43

14. Bar graphs showing percentage of parasitized fish and average total length

of fish grouped by species that were assessed in the field or laboratory

for glochidia in A, 2012; and B, 2013; as part of a mussel host-fish study,

central and southeastern Texas, 2012–13 ..............................................................................44

15. Bar graphs showing average number of juvenile mussels or glochidia

collected per fish species by site from fish held at the U.S. Fish and

Wildlife Service San Marcos National Fish Hatchery and Technology Center

in 2013 as part of a mussel host-fish study, central and southeastern

Texas, 2012–13.............................................................................................................................46

16. Graphs showing composite from all sites sampled in 2013 of A, average number of juvenile mussels or glochidia collected per fish

species; and B, total number of glochidia collected per fish species

from fish held at the U.S. Fish and Wildlife Service San Marcos National

Fish Hatchery and Technology Center as part of a mussel host-fish study,

central and southeastern Texas, 2012–13 ..............................................................................49
v

Tables

1. Study sites sampled for mussels and fish as part of a mussel host-fish

study, central and southeastern Texas, 2012–13.....................................................................5

2. Mussel survey results, including condition as part of a mussel

host-fish study, central and southeastern Texas, 2012–13 ..................................................14

3. Number of fish collected and glochidial parasitism by species from

sites sampled in 2012 as part of a mussel host-fish study, central and

southeastern Texas, 2012–13....................................................................................................19

4. Juvenile mussels or glochidia recovered from hatchery-held fish

collected in 2012 in central and southeastern Texas and submitted

to U.S. Fish and Wildlife Service National Fish Hatchery and Technology

Center in San Marcos, Tex., as part of a mussel host-fish study, 2012–13 .......................27

5. Number of fish collected and glochidial parasitism by species from

sites sampled in 2013 as part of a mussel host-fish study, central

and southeastern Texas, 2012–13 ............................................................................................33

6. Juvenile mussels or glochidia recovered from hatchery-held fish

collected in 2013 in central and southeastern Texas and submitted

to U.S. Fish and Wildlife Service National Fish Hatchery and Technology

Center in San Marcos, Tex., as part of a mussel host-fish study, 2012–13 .......................47

Conversion Factors and Datums

SI to Inch/Pound

Multiply By To obtain

Length

millimeter (mm) 0.0394 inch (in.)

centimeter (cm) 0.394 inch (in.)

meter (m) 3.28 foot (ft)

kilometer (km) 0.6215 mile (mi)

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as °F = (1.8 × 

°C) + 32.

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
vi
Abundance of Host Fish and Frequency of Glochidial 

Parasitism in Fish Assessed in Field and Laboratory 

Settings and Frequency of Juvenile Mussels or Glochidia 

Recovered from Hatchery-Held Fish, Central and 

Southeastern Texas, 2012–13 

By Christopher L. Braun,1 Charrish L. Stevens,2 Patricia D. Echo-Hawk,2 Nathan A. Johnson1, and

James B. Moring1

Abstract

In 2012–13, the U.S. Geological Survey (USGS), in 

cooperation with the U.S. Fish and Wildlife Service (USFWS), 

completed the first phase of a two-phase study of mussel 

host-fish relations for five endemic mussel species in central 

and southeastern Texas that were State-listed as threatened on 

January 17, 2010: (1) Texas fatmucket (Lampsilis bracteata), 

(2) golden orb (Quadrula aurea), (3) smooth pimpleback 

(Quadrula houstonensis), (4) Texas pimpleback (Quadrula 

petrina), and (5) Texas fawnsfoot (Truncilla macrodon). On 

October 6, 2011, the USFWS announced the completion of 

a status review and determined that the five mussel species 

warranted listing under the Endangered Species Act; however, 

listing of these species at that time was precluded by higher 

priority listing actions, and currently (December 2014), they 

remained unlisted. 

Freshwater mussels are long-lived, sedentary organisms 

that spend their larval stage as obligate parasites on the gills 

or fins of fishes, and many of these larvae, which are referred 

to as “glochidia,” can survive only on a narrow range of 

host-fish species. Results from both study phases are likely to 

provide information useful for propagation of rare mussels, 

reintroduction of host fish, population and reproduction 

monitoring, habitat restoration and enhancement, and adaptive 

management.

The abundance of host fish, frequency of parasitism in 

fish, and frequency of juvenile mussels or glochidia recovered 

from hatchery-held fish was assessed by collecting fish and 

mussels at 14 sites distributed among seven streams in central 

and southeastern Texas (juvenile mussels and glochidia were 

not differentiated in hatchery-held fish). All fish collected and 

assessed in this study were wild-caught. Qualitative surveys 

of the resident mussel communities were made, focusing on 

the five candidate species. A subsample (3 percent in 2012 and 

19 percent in 2013) of the fish collected during aquatic biota 

surveys was submitted to the USFWS San Marcos National 

Fish Hatchery and Technology Center to collect juvenile 

mussels and glochidia recovered from the host fish, which 

were held for 28 days in holding tanks to allow time for most 

of the attached glochidia to release from the gills of the fish 

after transforming into juvenile mussels. All fish not sent to 

the hatchery were assessed for glochidia in the field or in the 

USGS Texas Water Science Center laboratory in Austin, Tex. 

Juvenile mussels and glochidia that were recovered from fish 

at the hatchery were submitted for use in the second phase 

of this study, the development of deoxyribonucleic acid 

(DNA) identification keys to determine mussel and host-fish 

relationships through DNA-based molecular identification 

(DNA typing of the juvenile mussels and glochidia). Reporting 

on the results of DNA-based molecular identification research 

is beyond the scope of this report.

In 2012, the majority of the fish that were collected, 

in terms of total number and species types, belonged to the 

sunfish family Centrarchidae (centrarchids; 1,277 individuals 

and at least 10 species). Redbreast sunfish (Lepomis 

auritus) was the most common species collected in 2012 

(603 individuals), but the largemouth bass (Micropterus 

salmoides) species was caught at all 10 sites. The largest 

number of species (19) was collected at the San Saba Menard 

site (San Saba River near Menard, Tex.) on May 22, 2012. 

In 2013, most of the fish that were collected, in terms 

of total number and species types, were centrarchids 

(763 individuals) and cyprinids (10 species), respectively. 

Blacktail shiner (Cyprinella venusta) was the most common 

species collected in 2013 (287 individuals), but bluegill 

(Lepomis macrochirus) was the only species that was caught 

at all nine sites. The largest number of individuals (382) and 

1

U.S. Geological Survey.

2

U.S. Fish and Wildlife Service.
2 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

species (19) was collected from the Colorado Columbus site 

(Colorado River near Columbus, Tex.) on June 11, 2013. 

A minimum of two fish (any species) parasitized with 

glochidia was collected from each of the 10 sites sampled 

during 2012. The highest percentage of parasitized fish 

(19.1 percent) was measured at the Guadalupe Victoria site 

(Guadalupe River near Victoria, Tex.). The catfish family 

Ictaluridae (ictalurids) exhibited the highest proportion of 

parasitized fish (12.1 percent). Of the nine sites sampled in 

2013, the Pedernales Fredericksburg site (Pedernales River 

near Fredericksburg, Tex.) had the highest proportion of 

parasitized fish at 22.7 percent. Ictalurids again exhibited the 

highest frequency of parasitism (26.5 percent).

Of the fish that were not sent to the hatchery but assessed 

for glochidia in the field or in the laboratory in 2012, at least 

13 species were parasitized, and longear sunfish (Lepomis 

megalotis) was the species with the highest percentage of 

parasitized individuals (17.3 percent). Of the fish that were 

not sent to the hatchery but assessed for glochidia in the 

field or in the laboratory in 2013, only eight species were 

parasitized, and flathead catfish (Pylodictis olivaris) was the 

species with the highest percentage of parasitized individuals 

(42.9 percent).

With the exception of the San Antonio Charco site, fish 

were submitted to the hatchery from all sampling sites in 2013. 

During the first sampling period in 2013 (April 1–5), slightly 

more than half (16 out of 29) of the fish species (on a per site 

basis) that were submitted to the hatchery released juvenile 

mussels and glochidia. Compared to the other sampling 

periods in 2013, substantially fewer glochidia per fish were 

present on fish submitted to the hatchery during the second 

sampling period in 2013 (April 29–May 2). Although only 

two sites were sampled during the third sampling period in 

2013 (June 10–11), more juvenile mussels and glochidia were 

recovered at the hatchery during this sampling period (107) 

than were recovered during the first two sampling periods in 

2013 combined (102). An average of 17 juvenile mussels or 

glochidia was recovered per largemouth bass submitted to the 

hatchery from the Guadalupe Victoria site during the third 

sampling period.

A total of 19 fish species collected at nine sites was 

submitted to the hatchery in 2013, and 14 of these species 

had juvenile mussels or glochidia that were recovered at the 

hatchery. The three most productive species, in terms of the 

average number of juvenile mussels or glochidia recovered, 

were longear sunfish, spotted bass, and largemouth bass, 

each of which averaged more than two juvenile mussels or 

glochidia recovered per individual.

Introduction

Mussels play an important role in aquatic environments 

by modifying aquatic habitat to make it more suitable for 

themselves and other organisms. Mussels capture organic 

matter from the water column when they siphon, using 

it to build body and shell, while excreting nutrients that 

are immediately available to plant life. Mussels deposit 

any remaining organic material to the sediment, making it 

available for other invertebrates and fish to consume. During 

feeding, mussels filter the water they live in by removing 

phytoplankton as well as the fungi and bacteria attached to the 

organic particles they have removed from the water column. 

The mussel shells also act as a vital substrate on which algae 

and insect larvae attach. Because mussels anchor themselves 

to stream or lake bottoms, they may actually stabilize the 

lake or stream bottom, thereby minimizing scouring effects 

associated with floods and wave action. Mussels are also an 

important food source for several different kinds of terrestrial 

and aquatic animals, including muskrats and raccoons, as well 

as several species of fish (Minnesota Department of Natural 

Resources, 2014).

About 51 species of freshwater mussels live in Texas 

(Howells and others, 1996). In 2007 and 2008, the U.S. 

Fish and Wildlife Service (USFWS) was petitioned by 

the conservation group WildEarth Guardians (WildEarth 

Guardians, 2014) to list 12 freshwater mussel species that live 

in Texas and neighboring States as threatened or endangered 

with a need for species protection under the Endangered 

Species Act. Of the 12 mussel species endemic to central and 

southeastern Texas, 5 were selected as targeted mussel species 

for the determination of host-fish relationships documented 

in this report: (1) Texas fatmucket (Lampsilis bracteata), 

(2) golden orb (Quadrula aurea), (3) smooth pimpleback 

(Quadrula houstonensis), (4) Texas pimpleback (Quadrula 

petrina), and (5) Texas fawnsfoot (Truncilla macrodon). The 

five mussel species were State-listed as threatened on January 

17, 2010 (Texas Parks and Wildlife Department, 2010), and 

on October 6, 2011, the USFWS announced the completion 

of a status review and determined that the mussel species 

warranted listing under the Endangered Species Act (U.S. 

Fish and Wildlife Service, 2011c). Their listing at that time, 

however, was precluded by higher priority listing actions and 

currently (December 2014), they remained unlisted. Lack of 

adequate research on Texas freshwater mussels has resulted 

in little to no information on their biological and ecological 

needs, including habitat requirements and host-fish use. In 

some instances, the reduction in size of mussel populations has 

been caused by shifting fish community dynamics instead of 

the hydrological environment of the mussels themselves (Haag 

and Warren, 1998). 

In 2012–13, the U.S. Geological Survey (USGS), in 

cooperation with the USFWS, completed the first phase of a 

two-phase study of mussel host-fish relations for five endemic 

mussel species in central and southeastern Texas (fig. 1) that 

were State-listed as threatened on January 17, 2010. These 

freshwater mussel species are under a Federal Candidate 

Notice of Review by the USFWS (U.S. Fish and Wildlife 

Service, 2013) and were targeted for investigation in this 

study. The abundance of host fish, frequency of parasitism in 

fish, and frequency of juvenile mussels or glochidia recovered 
laf14-0664_fig01

!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

San Angelo

Austin

Corpus Christi

El Paso

San Antonio

Houston

Fort Worth

Dallas

Lubbock

Amarillo

Colorado San Saba

Colorado Nada

San Antonio Charco

San Saba 126

Colorado Garwood

Llano Castell

Llano Junction

Pedernales Fredericksburg

San Marcos Palmetto

San Saba Menard

Guadalupe Kerrville

Guadalupe Victoria

San Saba 208

Colorado Columbus

EXPLA

Basins and s (Texas fat pimpleba fawnsfoot and south Brazos Riv Colorado R San Saba  Llano Riv Pedernal Guadalupe  San Marc San Antoni Nueces RivStudy sites w Sampled in  Sampled in  Sampled in 

San Saba 208

Colorado Nada

Llano Junction

!

!

!

0 100 200 MILES

0 100 200 KILOMETERS

Brazos River

San Marcos

 River

GULF OF MEXICO

San Saba River

Llano River

San Antonio River

Guadalupe River

Pedernales River

Nueces

Rive r

Colorado River

Base modified from U.S. Geological Survey digital data, various scalesTexas Centric Mapping System, Albers Equal Area projectionNorth American Datum of 1983

35°

30°

95°

100°

105°

35

35

45

20

30

10

10

20

40

27

Figure 1. Location of sites sampled for fish and mussels in selected streams as part of a mussel host-fish study, central and southeastern Texas, 201
4 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

from hatchery-held fish was assessed by collecting fish and 

mussels at 14 sites distributed among seven streams in central 

and southeastern Texas. All fish collected and assessed in this 

study were wild-caught. In this report, the short names listed 

in table 1 are used for referring to sampling sites and are 

provided on all of the map-based figures.

Methods of investigation for the first phase of this twophase study are outlined in this report and include detailed 

descriptions of site selection and reconnaissance, mussel 

surveys, fish collection and field processing, glochidia 

recovery in the USGS Texas Water Science Center laboratory 

in Austin, Tex. (hereinafter referred to as “the laboratory”), 

along with juvenile mussel and glochidia recovery at the 

USFWS San Marcos National Fish Hatchery and Technology 

Center in San Marcos, Tex. (hereinafter referred to as “the 

hatchery”). Results from the first phase of the study are also 

described in this report and include abundance of host fish, 

frequency of parasitism in fish assessed for glochidia in 

the field and laboratory, and frequency of juvenile mussels 

or glochidia on hatchery-held fish. Juvenile mussels and 

glochidia that were recovered from fish at the hatchery, 

collected during the first phase of the study, were submitted 

for use in the second phase of this study for development of 

deoxyribonucleic acid (DNA) identification keys to determine 

mussel and host-fish relationships through DNA-based 

molecular identification (DNA typing of the juvenile mussels 

and glochidia) for the five mussel species of concern. Results 

from both study phases are likely to provide information 

useful for future recovery efforts that might include 

propagation of rare mussels, reintroduction of host fish, 

population and reproduction monitoring, habitat restoration 

and enhancement, and adaptive management.

Background Information 

Native freshwater mussels in the family Unionidae 

(unionids) have appreciably decreased in numbers and 

distribution throughout the United States (Randklev and 

others, 2009). It has been estimated that of the 297 species 

documented in the United States and Canada, 12 percent are 

thought to be extinct, 23 percent are considered threatened or 

endangered (Williams and others, 1993), and approximately 

43 percent are in need of conservation (Vaughn and Taylor, 

1999). Freshwater mussels possess a suite of biological 

characteristics that render them susceptible to reductions in 

habitat range, extirpation (local extinction), and extinction 

(Vaughn and Taylor, 1999). Unionids are long-lived, sedentary 

organisms that spend their larval stage as obligate parasites 

on the gills or fins of fishes, and many of these larvae (fig. 

2), which are referred to as “glochidia,” can survive only on 

a few host-fish species (Vaughn and Taylor, 1999; Randklev 

and others, 2009). As a result, extirpation and extinction of 

host-fish species, overharvesting of mussels, urban sprawl, 

stream impoundments, agriculture practices, introduction 

of alien species, and varied land-management policies have 

reduced or eliminated many unionid populations (Neck, 

1982; Bogan, 1993; Strayer, 1999; Vaughn and Taylor, 

1999; Watters, 1999; Lydeard and others, 2004). A major 

factor in the demise of freshwater mussels has been the 

large-scale impoundment of streams during the past 75 

years. Impoundments not only affect the free-flowing state 

of the stream but also affect the ability of fish to migrate 

longitudinally, which can affect mussel distribution and 

population structure (Vaughn and Taylor, 1999).

Knowledge of host fish is essential for understanding 

both mussel abundance and patterns of mussel distribution; 

this knowledge is also essential for the development of 

effective conservation programs (Haag and Warren, 1998). 

Poor recruitment in some mussel populations has been 

attributed to the lack of proper fish hosts caused by humaninduced changes in the fish assemblage (Haag and Warren, 

1998). If populations of the primary host fish for mussels 

decline, it is likely that mussel populations that depend on 

these hosts will also decline (Ziuganov and others, 2001). 

An increase in nonnative fish or changes in the presence 

or abundance of native host fish can cause changes in fish 

community structure and composition, which can alter mussel 

and host-fish relationships. Conservation plans for native 

freshwater mussels should include detailed information about 

the host fish that are critical for completion of the life cycle of 

the mussel (Martel and Lauzon-Guay, 2005). 

In the second phase of the study, and only mentioned 

in this report to provide additional context for the results 

described in this report, the collection of tissue samples to 

develop a DNA library from adult mussels began in 2009 

and continues to the present (2014). This library has many 

applications and can be used to determine host-fish use in 

the wild for the five candidate mussel species by capturing 

naturally parasitized fish and identifying juvenile mussels 

or glochidia by using DNA-based molecular identification 

data. Juvenile mussels and glochidia were submitted for DNA 

typing that were collected from 1 of 2 sources, either hatcheryheld fish or fish that were assessed for glochidia in the field or 

the laboratory (only glochidia that were still attached to fish 

were collected in the field or laboratory). Previous studies in 

different parts of the United States have used a DNA-typing 

approach to identify relations between mussels and their host 

fish in the Pacific Northwest (Gustafson and Iwamoto, 2005), 

Maine (Kneeland and Rhymer, 2008), and more recently, 

the St. Croix River in Minnesota (Boyer and others, 2011). 

Plans are that all DNA data obtained from this assessment of 

five threatened mussels and their host fish in Texas will be 

submitted to public DNA databanks, and all specimens will be 

vouchered in public museums to ensure open access to data.
Table 1. Study sites sampled for mussels and fish as part of a mussel host-fish study, central and southeastern Texas, 2012–13.[USGS, U.S. Geological Survey; --, not sampled]

USGS station 

number USGS station name

Short name 

(unique site 

identifier 

assigned to 

each USGS 

station name) 

(figs. 1, 3, 4–10, 

12, and 15)

Reach 

midpoint 

latitude

(decimal 

degrees)

Reach 

midpoint 

longitude

(decimal 

degrees)

Approximate 

reach 

length 

(meters) 

Water 

temperature 

collected 

with a 

continuous 

temperature 

probe?

292652096225300 Colorado River below Farm Road 950 near Garwood, Tex. Colorado Garwood 29.4478 96.3813 1,600 no 

311221098340800 Colorado River below Highway 190 near San Saba, Tex. Colorado San 

Saba

31.2057 98.5689 200 yes 

292341096192900 Colorado River near County Road 475 near Nada, Tex. Colorado Nada 29.3946 96.3247 1,200 no 

294040096310200 Colorado River near Kleimann Road near Columbus, Tex. Colorado Columbus 29.6779 96.5173 610 no 

284952097033200 Guadalupe River at Highway 77 near Victoria, Tex. Guadalupe Victoria 28.8311 97.059 200 no 

300300099093300 Guadalupe River near Concho Drive at Kerrville, Tex. Guadalupe Kerrville 30.05 99.1592 350 yes 

304212098573100 Llano River at Farm Road 2768 at Castell, Tex. Llano Castell 30.7032 98.9586 400 no 

303520099355100 Llano River at County Road 385 near Junction, Tex. Llano Junction 30.589 99.5976 460 no 

301316098540200 Pedernales River at Boos Lane near Fredericksburg, Tex.1 Pedernales Fredericksburg 230.2203, 330.2223 298.9003, 398.9033 2200; 3530 no 

08188200 San Antonio River near Charco, Tex. San Antonio 

Charco

28.7339 97.6431 210 no 

293519097350700 San Marcos River at Palmetto State Park, Tex. San Marcos Palmetto 29.5886 97.5852 330 no 

311418098360700 San Saba River at County Road 126 near San Saba, Tex. San Saba 126 31.2384 98.602 230 no 

311323098470500 San Saba River at County Road 208 near San Saba, Tex. San Saba 208 31.2231 98.7846 200 yes 

305358099543800 San Saba River below Beyer Crossing near Menard, Tex. San Saba Menard 30.8995 99.9107 1,250 yes 

1Study reach was downstream from Boos Lane bridge in 2012 and upstream from Boos Lane bridge in 2013.2In 2012.3In 2013.
laf14-0664_fig02 

Fish host Adult Sub-adult Fertilization Glochidia (young larvae) Glochidia on gills, fins, or epidermis MUSSEL LIFE CYCLE Mantle lure Female Male EXPLANATION Figure 2. Life cycle of unionid mussels native to Texas.
Methods of Investigation 7

Historical Range and Recent (2011) Occurrence 

of Target Mussel Species

Texas fatmucket, golden orb, smooth pimpleback, Texas 

pimpleback, and Texas fawnsfoot were once widely distributed 

throughout the major river basins of central and southeastern 

Texas (U.S. Fish and Wildlife Service, 2011b). As of the status 

review in 2011, each of the species was found in low densities 

at reduced locations. Texas fatmucket was found historically 

in large sections of the Colorado, Guadalupe, and San Antonio 

River Basins, but its known range has been reduced to include 

only parts of eight counties and no longer includes the San 

Antonio River or its tributaries (fig. 3). Golden orb was 

found historically in large sections of the San Antonio and 

Guadalupe River Basins and in a small section of the Nueces 

River Basin, but its known range has been reduced to include 

only parts of seven counties (fig. 4). Smooth pimpleback was 

found historically in large parts of the Brazos and Colorado 

River Basins, but its known range has been reduced to include 

only parts of 16 counties located almost exclusively in the 

lower halves of each basin (fig. 5). Texas pimpleback was 

found historically in most of the Guadalupe River Basin in 

addition to large parts of the Colorado and San Antonio River 

Basins, but its known range has been reduced to include only 

parts of five counties (fig. 6). Texas fawnsfoot was found 

historically in most of the Brazos and Colorado River Basins, 

but its known range has been reduced to 12 counties on the 

upper and lower Brazos River and middle and lower Colorado 

River (fig. 7).

Purpose and Scope

The purpose of this report is to describe the abundance 

of host fish, frequency of parasitism in fish assessed for 

glochidia in the field and in laboratory settings, and frequency 

of juvenile mussels or glochidia on hatchery-held fish at 14 

stream sites in central and southeastern Texas during 2012–13. 

Qualitative surveys of the resident mussel communities 

were made, focusing on the five candidate species for listing 

under the Endangered Species Act (Texas fatmucket, golden 

orb, smooth pimpleback, Texas pimpleback, and Texas 

fawnsfoot). Reporting on the results of DNA-based molecular 

identification of juvenile mussels and glochidia is beyond the 

scope of this report.

Methods of Investigation 

The Colorado, Guadalupe, and San Antonio River 

Basins were selected for fish and mussel sampling on the 

basis of historical ranges and known counties of recent (2011) 

occurrence for each of the target mussel species (U.S. Fish 

and Wildlife Service, 2011a; figs. 3–7). Sampling locations 

on streams in each river basin were chosen on the basis of 

the number of candidate mussels likely present at each site, 

accessibility to the sites, and satellite imagery. Satellite imagery 

provides evidence of desirable site characteristics, such as 

overhanging vegetation (which provides fish cover) and the 

presence of multiple mesohabitat types, and helps to confirm 

site accessibility.

A subsample of fish collected during aquatic biota surveys 

was submitted to the hatchery to collect juvenile mussels from 

host fish, which were held in holding tanks to allow time for 

most of the attached glochidia to mature and release from the 

gills of the fish. The fish that were not sent to the hatchery were 

assessed for glochidia in the field or in the USGS laboratory 

in Austin, Tex., and encysted glochidia were extracted in the 

laboratory, if present. Juvenile mussels and glochidia recovered 

at the hatchery were submitted to Nathan Johnson (research 

biologist with the USGS Southeast Ecological Science Center 

in Gainesville, Florida) for use in the second phase of this 

study, the development of DNA identification keys to determine 

mussel and host-fish relationships through DNA typing of the 

juvenile mussels and glochidia.

Site Selection and Reconnaissance 

Preliminary sites were selected on the basis of 

recommendations from experts in the field of freshwater 

mussels in Texas (Lyubov Burlakova, State University of New 

York at Buffalo, oral commun., 2012; Robert G. Howells, 

BioStudies, oral commun., 2012; Alexander Karatayev, State 

University of New York at Buffalo, oral commun., 2012; and 

Charles Randklev, Texas A&M Institute of Renewable Natural 

Resources, oral commun., 2012–13), in addition to professional 

judgment of the authors. After the preliminary sites were 

selected, field reconnaissance of the sites was done to reduce 

the number of final sampling sites. Attempts were made to 

find representative sites from the upper and lower parts of the 

Colorado, Guadalupe, and San Antonio River Basins; however, 

this was not attainable for the upper part of the San Antonio 

River, so only the lower part of the San Antonio River was 

sampled.

Established populations of the five candidate mussel 

species are distributed among the Brazos (smooth pimpleback 

and Texas fawnsfoot), Colorado (Texas fatmucket, smooth 

pimpleback, Texas pimpleback, and Texas fawnsfoot), 

Guadalupe (Texas fatmucket, golden orb, and Texas 

pimpleback), San Antonio (Texas fatmucket, golden orb, and 

Texas pimpleback), and Nueces (golden orb) River Basins 

(Howells and others, 1996). All five candidate species were 

considered initially because of the uncertainty associated with 

historical records and recent (2011) records on locations where 

these species have been found. Historical records on occurrence 

and follow-up site reconnaissance were used to locate candidate 

mussel populations. Mussel populations were considered 

acceptable for study if indicators of successful recruitment were 

present. Indicators of successful recruitment include a broad 

range in size classes (and presumably ages) (Darr and others, 

2013) and presence of subadult mussels (fig. 2).
laf14-0664_fig03 *This species is not necessarily d

recent occurrence and could be reFor more detailed information on  http://www.fws.gov/southwest/

Tex K  HiBas o B C    G  S NStu S S S

San Saba 208 Colorado Nada Llano Junction 0 25 50 MILES 0 25 50 KILOMETERS Base modified from U.S. Geological Survey digital data, various scales Texas Centric Mapping System, Albers Equal Area projection North American Datum of 1983 32° 31° 30° 29° 101° 100° 99° 98° 97° 96° San Angelo San Antonio Austin RUNNELS COUNTY MENARD COUNTY KIMBLE COUNTY MASON COUNTY GILLESPIE COUNTY LLANO COUNTY KERR COUNTY TRAVIS COUNTYBrazos River GULF OF MEXICO San Saba River Llano River San Antonio River Pedernales River Nueces River Colorado River Guadalupe River San Marcos River 

A

Colorado San Saba Colorado Nada Colorado Columbus San Antonio Charco San Saba 126 Colorado Garwood Llano Castell Llano Junction Pedernales Fredericksburg San Marcos Palmetto San Saba Menard Guadalupe Kerrville Guadalupe Victoria San Saba 208 35 35 10 10 37 Figure 3. Historical range for the Texas fatmucket (Lampsilis bracteata) and counties of known recent (2011) occurrence as part of a mussel host-fis

southeastern Texas.
laf14-0664_fig04

Gol K  H Bas o B C    G  S NStu S S S

Guadalupe Victoria

San Antonio Charco

San Marcos Palmetto

KERRCOUNTY

GUADALUPE

COUNTY

CALDWELL

COUNTY

GONZALES COUNTY

VICTORIA COUNTY

GOLIAD

COUNTY

LIVE OAK

COUNTY GULF OF MEXICO

San Antonio River

Pedernales River

Nueces River

Colorado River

Guadalupe

R

iv

e

r

San Marcos River

*This species is not necessarily drecent occurrence and could be reFor more detailed information on  http://www.fws.gov/southwest/

Base modified from U.S. Geological Survey digital data, various scalesTexas Centric Mapping System, Albers Equal Area projectionNorth American Datum of 1983

San Antonio

Austin

30°29°28°

99° 98° 97°

0 25 50 MILES

0 25 50 KILOMETERS

San Antonio Charco Guadalupe Victoria

Pedernales Fredericksburg

San Marcos Palmetto

Guadalupe Kerrville

A

35

35

10

10

37

Figure 4. Historical range for the golden orb (Quadrula aurea) and counties of known recent (2011) occurrence as part of a mussel host-fish study, c

southeastern Texas.
laf14-0664_fig05 *This species is not necessarily d

recent occurrence and could be reFor more detailed information on  http://www.fws.gov/southwest/

Smo Kn  HisBas o B Co    G  Sa NStu Sa Sa Sa

San Saba 208 Colorado Nada Llano Junction 0 50 100 MILES 0 50 100 KILOMETERS Base modified from U.S. Geological Survey digital data, various scales Texas Centric Mapping System, Albers Equal Area projection North American Datum of 1983 101° 100° 99° 98° 97° 96° 33° 32° 31° 30° 29° Houston Dallas Fort Worth San Angelo San Antonio Austin HAMILTON COUNTY CORYELL COUNTY MCLENNAN COUNTY BURNET COUNTY SAN SABA COUNTY FALLS COUNTY MILAM COUNTY LEON COUNTY BRAZOS COUNTY BURLESON COUNTY COUNTY GRIMES WASHINGTON COUNTY WALLER COUNTYCOLORADO COUNTY WHARTON COUNTY ROBERTSON COUNTY Brazos River San Saba River Llano River San Antonio River Pedernales River Nueces River Colorado RiverGuadalupe River San Marcos River GULF OF MEXICO 

A

Colorado San Saba Colorado Nada olorado Nada Colorado Columbus Columbus San Saba 126 Colorado Garwood olorado Garwood Llano Junction Llano Castell Pedernales Fredericksburg San Marcos Palmetto San Saba MenardGuadalupe Kerrville San Saba 208 35 35 10 10 37 35 35E 35W 20 20 30 Figure 5. Historical range for the smooth pimpleback (Quadrula houstonensis) and counties of known recent (2011) occurrence as part of a mussel h

southeastern Texas.
laf14-0664_fig06

*This species is not necessarily drecent occurrence and could be reFor more detailed information on  http://www.fws.gov/southwest/

Tex Kn  His Bas o B Co    G  Sa NStu Sa Sa Sa

San Saba 208

Colorado Nada

Llano Junction

0 25 50 MILES

0 25 50 KILOMETERS

Base modified from U.S. Geological Survey digital data, various scalesTexas Centric Mapping System, Albers Equal Area projectionNorth American Datum of 1983

101° 100° 99° 98° 97° 96°

29°30°31°32°

San Angelo

Austin

San Antonio

RUNNELS

COUNTY

CONCHO

COUNTY

SAN SABA

COUNTY

HAYS

COUNTY

VICTORIA COUNTY

Brazos River

San Saba River

Llano River

Pedernales River

Nueces

River

Colorado River

Guadalupe River San Marcos River

San Antonio River GULF OF MEXICO

UNITED STATES MEXICO

Colorado San Saba

San Saba 126

Llano Junction Llano Castell

Pedernales Fredericksburg

San Marcos Palmetto

San Saba Menard

Guadalupe Kerrville

San Saba 208

Colorado Nada

Colorado Columbus

Colorado Garwood

San Antonio Charco

Guadalupe Victoria

35

35

10

37

35

10

45

Figure 6. Historical range for the Texas pimpleback (Quadrula petrina) and counties of known recent (2011) occurrence as part of a mussel host-fish 

southeastern Texas.
laf14-0664_fig07 *This species is not necessarily d

recent occurrence and could be reFor more detailed information on  http://www.fws.gov/southwest/

Tex K  HiBas o B C    G  S NStu S S S

San Saba 208 Colorado Nada Llano Junction 0 50 100 MILES 0 50 100 KILOMETERS Base modified from U.S. Geological Survey digital data, various scales Texas Centric Mapping System, Albers Equal Area projection North American Datum of 1983 101° 100° 99° 98° 97° 96° 33° 32° 31° 30° 29° San Angelo Austin Houston Dallas San AntonioFort Worth COUNTY FALLS YOUNG COUNTY SHACKELFORD COUNTYSTEPHENS COUNTY SAN SABA COUNTY BURLESON COUNTYCOUNTY BRAZOS COUNTY GRIMES WASHINGTON COUNTY COLORADO COUNTY AUSTIN COUNTY WALLER COUNTY Brazos River GULF OF MEXICO San Saba River Llano River San Antonio River Pedernales River Nueces River Colorado River Guadalupe River San Marcos River 

UNITED STATES MEXICO Colorado Nada Colorado Columbus Columbus Colorado Garwood Colorado San Saba San Saba 126 Llano Castell Llano Junction Pedernales Fredericksburg San Marcos Palmetto San Saba Menard Guadalupe Kerrville San Saba 208 35 35 10 20 37 35E 35W35 10 20 3045 Figure 7. Historical range for the Texas fawnsfoot (Truncilla macrodon) and counties of known recent (2011) occurrence as part of a mussel host-fis

southeastern Texas.
Methods of Investigation 13

Ten sites on six different streams were sampled in 2012 

(table 1); five sites were resampled in 2013 because they 

offered a combination of living target mussel species and large 

proportions of fish parasitized with glochidia. In five cases, 

sites that had been selected for sampling in 2012 had to be 

replaced with alternate sites in 2013 for a variety of reasons. 

U.S. Geological Survey station names are listed for all sites 

sampled in 2012 and 2013 in table 1.

Sites on the lower Colorado River (Colorado Garwood, 

Colorado Nada, and Colorado Columbus; fig. 1, table 1) were 

each sampled only once. The Colorado Garwood site was 

replaced by the Colorado Nada site in hopes of collecting fish 

that were parasitized with Texas fawnsfoot glochidia because 

of the presence of abundant Texas fawnsfoot shell material 

at the Colorado Nada site. The Colorado Nada site was then 

replaced by the Colorado Columbus site in an effort to collect 

a larger proportion of fish that were parasitized with Texas 

fawnsfoot glochidia. Sites on the Llano River (Llano Castell 

and Llano Junction; fig. 1, table 1) and the San Marcos River 

(San Marcos Palmetto; fig. 1, table 1) were not revisited in 

2013. Relatively low proportions of parasitized fish were 

found at the sites on the Llano River, and none of the target 

mussel species were found at the Llano Castell site. Only one 

target mussel species (Texas fatmucket) was found at the site 

on the San Marcos River, a species that was well represented 

by the sites on the Guadalupe River.

One of the San Saba River sites (San Saba 126; fig. 1, 

table 1) had to be discontinued after it was sampled only once 

because mussels from another site on the San Saba River 

near County Road 340 were translocated to the San Saba 

126 site and scheduled for long-term monitoring by Texas 

A&M University. The Texas Department of Transportation, 

Texas Parks and Wildlife, and Texas A&M University were 

involved in the translocation effort. The San Saba 126 site was 

replaced with a second site on the San Saba River (San Saba 

208; fig. 1, table 1), which was located approximately 24 miles 

upstream from the San Saba 126 site to minimize disturbance 

to translocated mussels.

In 2013, a site was added on the San Antonio River (San 

Antonio Charco site; fig. 1, table 1) to provide coverage of an 

additional targeted river basin. A site was also added on the 

Colorado River (Colorado San Saba site; fig. 1, table 1) to 

provide additional coverage of the upper part of the Colorado 

River Basin.

As part of the reconnaissance process, continuous 

monitoring temperature probes were installed at four study 

sites (table 1) to measure and store water temperature at 

2-hour intervals. Water temperature data were collected on the 

basis that there might be a relation between water temperature 

and the number of parasitized fish collected (no relation was 

evident). The water temperature data were published in the 

USGS National Water Information System (U.S. Geological 

Survey, 2014) but are not further discussed in this report.

Mussel Surveys

At each sampling site, a search of all habitat types 

within the prescribed reach length (table 1) was done. Reach 

lengths varied from site to site on the basis of the need to 

sample the maximum number of mesohabitat (visually 

distinct units of habitat within a stream; [Pardo and Armitage, 

1997] with unique depths, velocities, slopes, substrates, and 

cover) types. Sampling followed the qualitative sampling 

methods outlined in Strayer and Smith (2003), specifically, 

random timed searches utilizing snorkeling, wading, and hand 

grubbing to approximately 15 centimeters (cm) deep; the 

utilization of viewing buckets where clear water conditions 

were present; or both. Search times varied at each site but 

generally were standardized to approximately 3 person-hours 

per site. Shorelines were searched for shell material to identify 

additional species that were not found along the prescribed 

reach length for a given search. Shell material was classified 

as fresh dead (periostracum present, nacre pearly, and soft 

tissue present); recent dead (periostracum mostly present, little 

fading of nacre, some algae stains, no tissue present); long 

dead (periostracum worn, nacre fading, lots of algae stains); 

or subfossil (little to no periostracum, white and chalky nacre, 

algae stains) (Texas Parks and Wildlife Department, 2014). 

The periostracum is the outermost, external layer of the shell, 

whereas the nacre is the pearly interior of the shell (Great 

Plains Nature Center, 2014). A species was considered extant 

at a site if it was represented by live or recently dead shell 

material (Szafoni, 2001). All mussels were identified by using 

standard taxonomic references (Howells and others, 1996; 

Neil Ford, University of Texas at Tyler, written commun., 

2010; Howells, 2010; Charles Randklev, Texas A&M Institute 

of Renewable Natural Resources, written commun., 2010), 

along with the USFWS reference collection housed at the 

Texas Coastal Ecological Services Field Office in Houston, 

Tex. After identification, mussels were returned to the stream 

as close as possible to where they were collected. Presence 

and absence data for different mussel species are shown in 

table 2.

Fish Collection and Field Processing

A fish assemblage survey was completed at each site 

during the spawning periods of targeted mussels, which varied 

by species. Timing of fish sampling was based on the best 

available knowledge and information gained during the initial 

mussel community surveys. All mesohabitats were sampled 

in a given reach, and efforts were made to sample for fish in 

areas where the targeted mussel species had been observed. 

Sampling methods were dependent on site conditions, 

fish assemblages, and abundance of target fish species. 

The same reaches that were sampled for mussels were also 

sampled for fish. To ensure that fish diversity and size-class 
Table 2. Mussel survey results, including condition as part of a mussel host-fish study, central and southeastern Texas, 2012–13. [USGS, U.S. Geological Survey; --, not collected; L, live; RD1, recent dead; LD2, long dead; SF3, subfossil; FD4, fresh dead] USGS station name Short name Mussel survey results, including con

Mussel species of interest Texas fatmucket (Lamsilis bracteata) Golden orb (Quadrula aurea) Smooth pimpleback (Quadrula houstonensis) T

pim

(Q

p

Colorado River below Farm Road 950 near Garwood, Tex. Colorado Garwood -- -- L/RD-LD L/

Colorado River below Highway 190 near San Saba, Tex. Colorado San Saba -- -- L/RD-LD L/

Colorado River near County Road 475 near Nada, Tex. Colorado Nada -- -- L/RD L/

Colorado River near Kleimann Road near Columbus, Tex. Colorado Columbus -- -- RD-LD R

Guadalupe River at Highway 77 near Victoria, Tex. Guadalupe Victoria -- L/RD-LD -- L/

Guadalupe River near Concho Drive at Kerrville, Tex.5 Guadalupe Kerrville L/RD-LD L/RD -- L/

Llano River at Farm Road 2768 at Castell, Tex. Llano Castell -- -- -- 

Llano River at County Road 385 near Junction, Tex. Llano Junction FD-RD -- -- 

Pedernales River at Boos Lane near Fredericksburg, Tex.6 Pedernales Fredericksburg FD-LD -- -- 

San Antonio River near Charco, Tex. San Antonio Charco -- L/RD-LD -- 

San Marcos River at Palmetto State Park, Tex. San Marcos Palmetto -- L/RD-D -- San Saba River at County Road 126 near San Saba, Tex. San Saba 126 -- -- L/RD-LD L/

San Saba River at County Road 208 near San Saba, Tex. San Saba 208 -- -- L/RD-LD L/

San Saba River below Beyer Crossing near Menard, Tex. San Saba Menard L/RD-LD -- -- F
Table 2. Mussel survey results, including condition as part of a mussel host-fish study, central and southeastern Texas, 2012–13.—Continued[USGS, U.S. Geological Survey; --, not collected; L, live; RD1, recent dead; LD2, long dead; SF3, subfossil; FD4, fresh dead]

Short name

Mussel survey results, including condition

Additional native mussel species

Threeridge 

(Amblema 

plicata)

Rock 

pocketbook 

(Arcidens confragosus)

Tampico 

pearly 

mussel 

(Cyrtonaias 

tampicoensis)

Southern 

mapleleaf 

(Quadrula 

apiculata)

False 

spike (Quadrula 

mitchelli)

Pistolgrip 

(Tritogonia 

verrucosa)

Louisiana 

fatmucket 

(Lampsilis 

hydiana)

Yellow 

sandshell 

(Lampsilis 

teres)

Fragile 

papershell

(Leptodea 

fragilis)

Washboard

(Megalonaias 

nervosa)

Bleufer 

(Potamilus 

purpuratus)

Giant 

floater 

(Pyganodon 

grandis)

Lil

(T

la

pa

va

Colorado Garwood L/RD-LD L/RD L/RD-LD L/RD-LD -- -- -- L/RD-LD L/RD-LD -- L/RD-LD L/RD L/R

Colorado San 

Saba

L/RD-LD -- L/RD-LD L/RD-LD -- L/RD-LD -- -- L/RD-LD -- L/RD-LD -- 

Colorado Nada L/RD-LD -- -- LD-SF -- -- -- L/RD-LD L/RD-LD -- -- -- 

Colorado Columbus RD-LD -- -- -- -- -- -- RD-LD L/RD-LD -- -- -- LD

Guadalupe Victoria L/RD-LD L/RD L/RD-LD L/RD-LD -- -- FD-RD L/RD-LD L/FD-RD L/RD L/RD -- 

Guadalupe Kerrville -- -- L -- -- -- -- -- -- -- -- -- L

Llano Castell -- -- -- -- -- -- -- -- -- -- -- -- 

Llano Junction -- -- -- -- -- -- -- -- -- -- -- -- 

Pedernales Fredericksburg -- -- -- -- -- -- -- -- -- -- -- -- 

San Antonio 

Charco

L/RD-LD L/RD -- -- -- L/RD-LD -- L/RD-LD -- RD -- -- 

San Marcos Palmetto L/RD-LD -- RD -- SF LD -- L/RD-LD -- -- -- -- 

San Saba 126 L/RD-LD -- -- -- -- L/RD-LD -- -- -- -- -- -- 

San Saba 208 L/RD-LD -- -- -- -- L/RD-LD -- -- L/RD-LD -- -- -- 

San Saba Menard RD -- L/RD L/RD -- L -- -- -- -- -- -- 

1Periostracum mostly present; little fading of nacre; some algae stains; no tissue present.2Periostracum worn; nacre fading; lots of algae stains.3Little to no periostracum; white and chalky nacre; algae stains.4Periostracum present; nacre pearly; soft tissue present.5Mussel survey area also includes small impoundment upstream from the Guadalupe Kerrville site.6Study reach was moved downstream from Boos Lane bridge in 2012 to upstream from Boos Lane bridge in 2013.
16 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

variability were surveyed efficiently at each site, available 

mesohabitat types were sampled by using a combination of 

boat and barge electrofishing and seining. Most sites were 

sampled primarily by using a barge that was followed closely 

by a second barge carrying multiple species-specific holding 

tanks. Fish were identified by a fish taxonomist as soon as 

they were netted and separated by species, when possible, 

into appropriate species-specific, aerated holding tanks to 

avoid potential glochidia loss or cross-contamination between 

species. Because of limited space, it was not always possible 

to keep very large fish separated by species. To ensure 

retention of glochidia that detached from fish during handling 

and transport, water from holding tanks was transferred to 

appropriate species-specific coolers that were used to transfer 

fish to the hatchery. Sites with wide channels and deep pools 

that could not be waded effectively were electrofished from a 

cataraft (raft with two pontoons); this included all of the sites 

on the Colorado River except the Colorado San Saba site and 

the San Saba Menard site (fig. 1, table 1). Seining was also 

done in many cases to supplement electrofishing efforts by 

using a 1.0- by 3.0-meter (m), 0.17-cm mesh, flat-panel seine. 

Seining was used when certain target families, particularly 

Percidae (percids), were not collected by electrofishing. To 

minimize holding times and stress during the transfer of 

potential host fish to the hatchery in 2013, fish collection 

activity was often curtailed after suitable quantities of target 

fish species had been collected; therefore, seining was 

infrequently part of the 2013 fish-sampling efforts.

After fish assemblage surveys were completed, the 

number and species of fish were selected for submittal to 

the hatchery. Members of different families were selected 

to provide a diverse selection of potential host fish. Fish 

species that had a high proportion of glochidia parasitism in 

2012 were targeted for submittal in 2013. Tanks were aerated 

during transport, and fish survival rate was high (greater than 

95 percent). 

Fish that were not submitted to the hatchery were 

measured to the nearest millimeter (mm) to determine total 

length. Fish that could be identified in the field and assessed 

for glochidia without a microscope (typically fish with total 

lengths greater than 100 mm) were returned to the stream if 

no glochidia were present. Forceps were used to check for 

glochidia on anterior and posterior surfaces of gill filaments 

on each arch and between gill filaments. If glochidia were 

observed, then the gill arch was removed and retained. If 

the fish was heavily infested, either the head or gill arches 

were preserved. Fish that could not be identified in the 

field or that could not be checked for glochidia effectively 

without a microscope were preserved in a 95-percent ethanol 

solution, labeled by site and date, and returned to the USGS 

Texas Water Science Center for preliminary identification. 

Ethanol solution was used in place of formalin because 

formalin degrades DNA and makes tissues unsuitable for 

analysis (Nathan A. Johnson, U.S. Geological Survey, written 

commun., 2014). All small fish (total lengths less than about 

100 mm) that were not submitted to the hatchery were retained 

to be assessed for glochidia at the USGS laboratory in Austin, 

Tex.

Fish that were identified in the field during sampling were 

identified to the lowest taxonomic level possible (generally 

species). All retained fish specimens were preserved in a 

70-percent ethanol solution and deposited with the Curator of 

Ichthyology at the University of Texas Natural Science Center 

in Austin, Tex., for taxonomic verification and permanent 

deposition (University of Texas, 2012).

Glochidia Recovery at U.S. Geological Survey 

Laboratory

Fish that were not submitted to the hatchery and could 

not be assessed for glochidia without a microscope were 

retained for evaluation by USGS personnel in a laboratory 

setting. Each fish was identified to species and measured for 

total length prior to examining both sets of gills for glochidia 

by using a microscope. When observed, glochidia were 

removed with a sterilized needle and placed into a microplate 

and preserved with 95 percent ethyl alcohol. A microplate 

is a series of small test tubes (wells) that are arranged on a 

plastic plate in a regular matrix pattern, most commonly with 

96 wells (Medical Museion, 2010). Site name, collection date, 

fish species, total length, and glochidia extraction location 

were recorded, and a unique sample identifier was assigned 

that corresponded to an individual well in the microplate. 

During the reconnaissance phase of the project (2012), 

excessive amounts of fish gill tissue were often included with 

the glochidia in the wells, which contaminated some of the 

samples prior to DNA typing, rendering them unusable. In 

2013, care was taken to reduce the amount of gill material that 

was attached to glochidia placed in each well.

Juvenile Mussel and Glochidia Recovery at the 

U.S. Fish and Wildlife Service Hatchery

At the hatchery operated by the USFWS, fish were 

separated by species and placed into holding tanks. Larger fish 

were placed in individual holding tanks, whereas smaller fish 

(such as cyprinids) of the same species were often grouped 

in a single holding tank. Fish were held at temperatures 

ranging from 21 to 24 degrees Celsius (°C). Results from 

a previous passive infestation trial (Johnson and others, 

2012) indicated that most transformations from glochidia 

to juvenile mussels occurred between 17 and 26 days on 

four different species of fish for the Texas fatmucket, one 

of the target mussel species in this study, so holding tanks 

were siphoned daily for the first 28 days of each trial. Shell 

length, height, and hinge length were measured to the nearest 

0.01 mm for juvenile mussels and glochidia (fig. 2), and the 
Abundance of Host Fish 17

number of juvenile mussels or glochidia recovered per fish 

was tabulated. Not all glochidia transformed into juvenile 

mussels, and the hatchery did not differentiate glochidia 

recovered from host fish from the juvenile mussels that had 

transformed from glochidia. Only juvenile mussels that have 

detached from the host fish are viable; the glochidia that 

have detached from the host fish are not viable and will not 

develop into juvenile mussels (Hambrook and Eberle, 2000). 

Each juvenile mussel or glochidium that was recovered was 

preserved individually in 95 percent ethyl alcohol for DNAbased molecular identification (DNA results are not discussed 

in this report). Because a small number of the glochidia did 

not release from the host fish during the 28-day trials, not all 

glochidia were recovered at the hatchery. In these cases, fish 

were returned to the USGS to be examined in a laboratory for 

additional glochidia. Identifying the species of glochidia that 

were still attached to the fish returned to the USGS laboratory 

was not completed and would not indicate mussel-to-host-fish 

relations, because the glochidia will attach to nonhosts but will 

not complete metamorphosis to a free-living juvenile mussel. 

Studies have shown that glochidia will attach to nonhosts 

without complete metamorphosis (Lellis and others, 2013) 

and, in some cases, will attach to inanimate objects (Haag, 

2012). In addition, some glochidia that were observed on 

fish that were returned by the hatchery for examination in the 

USGS laboratory may not have had sufficient time to reach 

maturity over the course of the 28-day trial.

Quality Assurance

Field identification of fish was done with the aid of 

appropriate taxonomic keys by trained biologists familiar with 

the types of fish taxa found in central and southeastern Texas. 

Unidentified fish taxa retained for laboratory identification 

were provided to the Curator of Ichthyology at the University 

of Texas Natural Science Center in Austin, Tex., for taxonomic 

verification and permanent deposition (University of Texas, 

2012). Field identification of mussels was done by trained 

biologists familiar with the freshwater species present in 

central and southeastern Texas with the aid of field guides 

for mussel species in Texas or with the help of other expert 

mussel biologists from Texas Parks and Wildlife and Texas 

A&M University. All fish and mussel voucher specimens were 

labeled onsite and will be retained at the USGS laboratory in 

Austin or the University of Texas Natural Science Center in 

Austin for a minimum of 5 years. 

Abundance of Host Fish

In 2012, fish belonging to 12 families (fig. 8; composite 

of data from tables 3 and 4) were collected as potential hosts. 

The majority of the fish that were collected, in terms of total 

number and species type, belonged to the sunfish family 

Centrarchidae (centrarchids) and the carp and minnow family 

Cyprinidae (cyprinids). A total of 1,277 individuals and at 

least 10 different species of centrarchids (the number of 

different species could be higher depending on the identity 

of the unknown members of the Micropterus genus that were 

collected) and a total of 623 individuals and at least 9 different 

species of cyprinids (the number of different species could be 

higher depending on the identity of the unknown members 

of the Cyprinidae family that were collected) were collected 

in 2012 (fig. 8; composite of data from tables 3 and 4). 

Redbreast sunfish (Lepomis auritus) was the most common 

species collected in 2012 (603 individuals) (fig. 8; composite 

of data from tables 3 and 4). Other common species were 

blacktail shiner (Cyprinella venusta, 353 individuals) and 

longear sunfish (Lepomis megalotis, 220 individuals). The 

largest number of individuals (416) was collected at the Llano 

Castell site on August 22, 2012, whereas the largest number 

of species (19) was collected at the San Saba Menard site 

on May 22, 2012 (composite of data from tables 3 and 4). 

The fewest number of individuals (62) and species (7) was 

collected at the Guadalupe Kerrville site (fig. 1, table 1) on 

May 29, 2012 (composite of data from tables 3 and 4). Fewer 

than 10 individuals of a given species were collected for 20 

out of the 38 species (excluding the unknown species that 

were collected) across all 10 sites sampled for fish during 

2012. Largemouth bass (Micropterus salmoides) were caught 

at all 10 sites, and four other species (bluegill [Lepomis 

macrochirus], longear sunfish, blacktail shiner, and channel 

catfish [Ictalurus punctatus]) were caught at 9 of the 10 sites.

In 2013, fish belonging to 11 families (fig. 9; composite 

of data from tables 5 and 6) were collected as potential hosts. 

The majority of the fish that were collected in 2013, in terms 

of total number and species types, were centrarchids and 

cyprinids, respectively. A total of 686 individuals and 10 

species of centrarchids and a total of 763 individuals and 6 

species of cyprinids were collected in 2013 (fig. 9; composite 

of data from tables 5 and 6). Blacktail shiner was the most 

common species collected in 2013 (287 individuals) (fig. 

9; composite of data from tables 5 and 6). Other common 

species were red shiner (Cyprinella lutrensis, 263 individuals) 

and longear sunfish (238 individuals). The largest number 

of individuals (382) and species (19) was collected from 

the Colorado Columbus site on June 11, 2013. The fewest 

number of individuals (53) was collected from the San Saba 

Menard site on April 5, 2013, whereas the fewest number of 

species (n=5) was collected at the Pedernales Fredericksburg 

site (fig. 1, table 1) on May 1, 2013 (composite of data from 

tables 5 and 6). Fewer than 10 individuals of a given species 

were collected for 13 out of the 34 species that were collected 

across all 10 sites. Bluegill was the only species that was 

caught at all 9 sites that were sampled in 2013, whereas 

largemouth bass, longear sunfish, and bullhead minnow 

(Pimephales vigilax) were caught at 7 out of 9 sites.
18 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0644_fig 08

River carpsucker

Smallmouth buffalo

Gray redhorse

Redbreast sunfish

Green sunfish

Warmouth

Orangespotted sunfish

Bluegill

Longear sunfish

Redear sunfish

Spotted bass

Largemouth bass

Rio Grande cichlid

Gizzard shad

Central stoneroller

Red shiner

Blacktail shiner

Common carp

Burrhead chub

Bullhead minnow

Blackstripe topminnow

Channel catfish

Flathead catfish

Spotted gar

Longnose gar

Orangethroat darter

Texas logperch

Dusky darter

Western mosquitofish

Freshwater drum

Spotted sucker

Unknown Micropterus

White crappie

Mexican tetra

Threadfin shad

Texas shiner

Ghost shiner

Mimic shiner

Unknown Cyprinidae

Bigscale logperch

Unknown Percidae

Fish species common name

Number of fish caught

700

100

200

300

400

500

0

600

San Marcos Palmetto (8/24/2012)

Pedernales Fredericksburg (8/23/2012)

Llano Junction (8/22/2012)

Llano Castell (8/22/2012)

San Saba 208 (8/21/2012)

Colorado Garwood (5/31/2012)

Guadalupe Victoria (5/30/2012)

Guadalupe Kerrville (5/29/2012)

San Saba Menard (5/22/2012)

San Saba 126 (5/21/2012)

EXPLANATION

 Site short name and date sampled (table 1)

Catostomidae

Centrarchidae

Characidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

 Family names for fish species collected 

Figure 8. Abundance of potential host fish from sites sampled in 2012 as part of a mussel host-fish study, central and southeastern 

Texas, 2012–13.
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Genus and species Species common name

Short name (fig. 1) with 2012 sampling date in pare

San Saba 126 (5/21) San Saba Menard (5/22) 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

N

Catostomidae Carpiodes carpio River carpsucker 1 30 0

Ictiobus bubalus Smallmouth 

buffalo

Minytrema melanops Spotted suckerMoxostoma congestum Gray redhorse 2 438 0 19 415 0

Centrarchidae Lepomis auritus Redbreast sunfish 200 122 5 

Lepomis cyanellus Green sunfish 2 43 0 2 153 0Lepomis gulosus Warmouth 5 91 0

Lepomis humilis Orangespotted 

sunfish

Lepomis macrochirus Bluegill 5 54 2 13 68 1 Lepomis megalotis Longear sunfish 19 68 9 4 61 0 Lepomis microlophus Redear sunfish 1 145 0

Micropterus punctulatus Spotted bassMicropterus salmoides Largemouth bass 1 158 0 8 217 0 

Unknown members of Micropterus genus 1 35 0 

Pomoxis annularis White crappie

Characidae Astyanax mexicanus Mexican tetra

Cichlidae Herichthys 

cyanoguttatum

Rio Grande 

cichlid

Clupeidae Dorosoma cepedianum Gizzard shad 1 310 0 1 410 0

Dorosoma petenense Threadfin shad

Cyprinidae Campostoma anomalum Central stoneroller

Cyprinella lutrensis Red shiner 25 45 0Cyprinella venusta Blacktail shiner 22 61 0 24 49 2 

Cyprinus carpio Common carp 2 593 0 1 680 0Macrhybopsis marconis Burrhead chub

Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Genus and species Species common name Short name (fig. 1) with 2012 sampling date in pare

San Saba 126 (5/21) San Saba Menard (5/22) 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations N

Notropis amabilis Texas shiner Notropis buchanani Ghost shiner Notropis volucellus Mimic Shiner 9 41 0 Pimephales vigilax Bullhead minnow 7 43 1 Unknown members of Cyprinidae family Fundulidae Fundulus notatus Blackstripe topminnow Ictaluridae Ictalurus punctatus Channel catfish 4 354 0 4 348 0 Pylodictis olivaris Flathead catfish 2 340 1 1 315 0 Lepisosteidae Lepisosteus oculatus Spotted gar Lepisosteus osseus Longnose gar 1 360 0 Percidae Etheostoma spectabile Orangethroat darter Percina carbonaria Texas logperch 9 83 1 2 58 0 Percina macrolepida Bigscale logperch 1 40 0 Percina sciera Dusky darter Unknown members of Percidae family 2 43 0 

Poeciliidae Gambusia affinis Western mosquitofish 3 32 0 Sciaenidae Aplodinotus grunniens Freshwater drum 3 458 0 Totals 107 106 14 300 137 8 

Percentage of fish infested with glochidia 13.1 2.7 

Total number of species 16 19 
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Genus and species Species common name

Short name (fig. 1) with 2012 sampling date in pare

Guadalupe Victoria (5/30) Colorado Garwood (5/31) 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

N

Catostomidae Carpiodes carpio River carpsucker 5 62 0

Ictiobus bubalus Smallmouth buffalo 4 518 0 1 610 0

Minytrema melanops Spotted sucker 1 350 0Moxostoma congestum Gray redhorse 

Centrarchidae Lepomis auritus Redbreast sunfish 1 45 0 2 60 1 

Lepomis cyanellus Green sunfish

Lepomis gulosus Warmouth 

Lepomis humilis Orangespotted 

sunfish

6 103 0

Lepomis macrochirus Bluegill 1 50 0 Lepomis megalotis Longear sunfish 41 63 14 42 61 7 

Lepomis microlophus Redear sunfishMicropterus punctulatus Spotted bass 4 150 0 1 160 1 

Micropterus salmoides Largemouth bass 4 96 2 27 185 3 

Unknown members of Micropterus genus 3 33 2

Pomoxis annularis White crappie 

Characidae Astyanax mexicanus Mexican tetra 2 40 0

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid

Clupeidae Dorosoma cepedianum Gizzard shad 3 77 0

Dorosoma petenense Threadfin shad 2 63 0 

Cyprinidae Campostoma anomalum Central stoneroller

Cyprinella lutrensis Red shiner 54 49 2 10 48 0 

Cyprinella venusta Blacktail shiner 5 50 0 Cyprinus carpio Common carp 

Macrhybopsis marconis Burrhead chub 2 55 0

Notropis amabilis Texas shiner 
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Genus and species Species common name Short name (fig. 1) with 2012 sampling date in pare

Guadalupe Victoria (5/30) Colorado Garwood (5/31) 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations N

Notropis buchanani Ghost shiner Notropis volucellus Mimic Shiner Pimephales vigilax Bullhead minnow 13 47 3 

Unknown members of Cyprinidae family Fundulidae Fundulus notatus Blackstripe topminnow 

Ictaluridae Ictalurus punctatus Channel catfish 8 239 4 3 303 1 

Pylodictis olivaris Flathead catfish 

Lepisosteidae Lepisosteus oculatus Spotted gar 3 427 0 Lepisosteus osseus Longnose gar 3 537 0 Percidae Etheostoma spectabile Orangethroat darter Percina carbonaria Texas logperch 

Percina macrolepida Bigscale logperch 1 60 0 Percina sciera Dusky darter Unknown members of Percidae family Poeciliidae Gambusia affinis Western mosquitofish Sciaenidae Aplodinotus grunniens Freshwater drum 1 440 0 Totals 141 84 27 112 129 13 

Percentage of fish infested with glochidia 19.1 11.6 

Total number of species 14 15 
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Genus and species Species common name

Short name (fig. 1) with 2012 sampling date in paren

Llano Castell (8/22) Llano Junction (8/22) Ped

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. 

fis

Catostomidae Carpiodes carpio River carpsucker

Ictiobus bubalus Smallmouth buffaloMinytrema melanops Spotted suckerMoxostoma congestum Gray redhorse 4 385 0 9 334 2

Centrarchidae Lepomis auritus Redbreast sunfish 281 113 4 19 107 1 8

Lepomis cyanellus Green sunfish 1 140 0 

Lepomis gulosus Warmouth 4 140 0 

Lepomis humilis Orangespotted 

sunfish

Lepomis macrochirus Bluegill 3 98 0 25 96 3 5Lepomis megalotis Longear sunfish 12 98 0 2

Lepomis microlophus Redear sunfish 3 188 0 Micropterus punctulatus Spotted bass 3 192 0 5 210 0

Micropterus salmoides Largemouth bass 22 132 0 14 121 0 5

Unknown members of Micropterus genus

Pomoxis annularis White crappie

Characidae Astyanax mexicanus Mexican tetra

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid 9 111 0 5 83 0

Clupeidae Dorosoma cepedianum Gizzard shad 1 330 0

Dorosoma petenense Threadfin shad

Cyprinidae Campostoma anomalum Central stoneroller 4 80 0 3

Cyprinella lutrensis Red shiner 2

Cyprinella venusta Blacktail shiner 78 70 0 55 77 0 6Cyprinus carpio Common carp 2 500 0Macrhybopsis marconis Burrhead chubNotropis amabilis Texas shiner
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Genus and species Species common name Short name (fig. 1) with 2012 sampling date in paren

Llano Castell (8/22) Llano Junction (8/22) Ped

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations No. 

fis

Notropis buchanani Ghost shiner 1 70 0 Notropis volucellus Mimic Shiner Pimephales vigilax Bullhead minnow 2 60 0 Unknown members of Cyprinidae family 2 73 0 Fundulidae Fundulus notatus Blackstripe topminnow Ictaluridae Ictalurus punctatus Channel catfish 1 115 0 6 230 2 

Pylodictis olivaris Flathead catfish 3 135 0 Lepisosteidae Lepisosteus oculatus Spotted gar Lepisosteus osseus Longnose gar 1 500 0 Percidae Etheostoma spectabile Orangethroat darter 1 40 0 Percina carbonaria Texas logperch 4 68 0 32 88 0 

Percina macrolepida Bigscale logperch Percina sciera Dusky darter Unknown members of Percidae family 2 58 0 Poeciliidae Gambusia affinis Western mosquitofish 1 55 0 

Sciaenidae Aplodinotus grunniens Freshwater drum Totals 416 111 4 199 112 8 36

Percentage of fish infested with glochidia 1.0 4.0 

Total number of species 16 17 
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Genus and species Species common name

Short name (fig. 1) with 2012 sampling date in parent

San Marcos Palmetto (8/24) Total - all sites (2012 only) Tot

No. of 

fish

Avg. 

total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. 

total 

length 

(mm)

No. of 

glochidia 

infestations

Percentage 

of fish 

infested

No. of 

fish

Catostomidae Carpiodes carpio River carpsucker 6 57 0 0

54 

Ictiobus bubalus Smallmouth buffalo 5 536 0 0

Minytrema melanops Spotted sucker 1 350 0 0

Moxostoma congestum Gray redhorse 2 253 0 42 372 2 4.8

Centrarchidae Lepomis auritus Redbreast sunfish 597 116 12 2.0

1,247 

Lepomis cyanellus Green sunfish 19 77 0 28 91 0 0

Lepomis gulosus Warmouth 16 129 0 0

Lepomis humilis Orangespotted 

sunfish 6 103 0 0

Lepomis macrochirus Bluegill 1 100 0 197 90 21 10.7

Lepomis megalotis Longear sunfish 48 106 6 208 83 36 17.3

Lepomis microlophus Redear sunfish 6 163 0 0

Micropterus punctulatus Spotted bass 7 239 0 22 198 1 4.5

Micropterus salmoides Largemouth bass 11 152 3 157 132 15 9.6

Unknown members of Micropterus genus 9 35 2 22.2

Pomoxis annularis White crappie 1 90 0 0

Characidae Astyanax mexicanus Mexican tetra 2 40 0 0 2 

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid 14 101 0 0 14 

Clupeidae Dorosoma cepedianum Gizzard shad 6 214 0 0

11 

Dorosoma petenense Threadfin shad 2 185 0 5 134 0 0
Table 3. Number of fish collected and glochidial parasitism by species from sites sampled in 2012 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Genus and species Species common name Short name (fig. 1) with 2012 sampling date in parent

San Marcos Palmetto (8/24) Total - all sites (2012 only) Tot

No. of fish Avg. total length (mm) No. of glochidia infesta- tions No. of fish Avg. total length (mm) No. of glochidia infesta- tions Percent- age of fish infested No. of fish 

Cyprinidae Campostoma anomalum Central stoneroller 38 78 0 0 581 

Cyprinella lutrensis Red shiner 36 72 0 156 58 2 1.3 Cyprinella venusta Blacktail shiner 2 70 0 333 71 2 0.6 Cyprinus carpio Common carp 11 533 0 0 Macrhybopsis marconis Burrhead chub 2 55 0 0 Notropis amabilis Texas shiner 1 50 0 0 Notropis buchanani Ghost shiner 1 70 0 0 Notropis volucellus Mimic Shiner 9 41 0 0 Pimephales vigilax Bullhead minnow 2 68 0 28 50 4 14.3 Unknown members of Cyprinidae family 2 73 0 0 Fundulidae Fundulus notatus Blackstripe topminnow 5 66 0 0 5 

Ictaluridae Ictalurus punctatus Channel catfish 3 213 0 54 204 7 13.0 66 

Pylodictis olivaris Flathead catfish 2 260 0 12 217 1 8.3 Lepisosteidae Lepisosteus oculatus Spotted gar 1 510 0 4 448 0 0 9 

Lepisosteus osseus Longnose gar 5 494 0 0 Percidae Etheostoma spectabile Orangethroat darter 1 40 0 0 100 

Percina carbonaria Texas logperch 78 90 1 1.3 Percina macrolepida Bigscale logperch 2 50 0 0 Percina sciera Dusky darter 10 77 1 10 77 1 10.0 Unknown members of Percidae family 9 41 0 0 Poeciliidae Gambusia affinis Western mosquitofish 5 41 0 0 5 

Sciaenidae Aplodinotus grunniens Freshwater drum 4 454 0 0 4 

Totals 146 111 10 2,098 110 107 5.1 2,098 

Percentage of fish infested with glochidia 6.8 Total number of species 14
Frequency of Parasitism in Fish Assessed for Glochidia in Field and Laboratory Settings 27

Table 4. Juvenile mussels or glochidia recovered from hatchery-held fish collected in 2012 in central and southeastern Texas and 

submitted to U.S. Fish and Wildlife Service National Fish Hatchery and Technology Center in San Marcos, Tex., as part of a mussel hostfish study, 2012–13.

Short name Date Family Species 

common name1

Number of fish 

submitted to 

hatchery

Number of juvenile 

mussels or glochidia 

recovered from 

hatchery-held fish

Pedernales Fredericksburg 8/23/2012 Centrarchidae Redbreast sunfish 6 0

Pedernales Fredericksburg 8/23/2012 Centrarchidae Longear sunfish 6 0

Pedernales Fredericksburg 8/23/2012 Centrarchidae Largemouth bass 6 0

Pedernales Fredericksburg 8/23/2012 Cyprinidae Red shiner 12 2

Pedernales Fredericksburg 8/23/2012 Cyprinidae Blacktail shiner 10 1

Pedernales Fredericksburg 8/23/2012 Ictaluridae Channel catfish 1 0

San Marcos Palmetto 8/24/2012 Centrarchidae Longear sunfish 6 1

San Marcos Palmetto 8/24/2012 Centrarchidae Largemouth bass 6 2

San Marcos Palmetto 8/24/2012 Cyprinidae Red shiner 10 4

San Marcos Palmetto 8/24/2012 Cyprinidae Blacktail shiner 10 1

San Marcos Palmetto 8/24/2012 Percidae Dusky darter 2 0

Totals 75 11

1

All of the species listed in table 4 are among those listed in table 3.

In 2012, an average of 217 individuals and an average 

of 14.9 species were caught per site. In 2013, the average 

number of individuals and species caught decreased to 

151 and 11.7, respectively, per site (and per sampling period 

in the cases of the Guadalupe Victoria site [fig. 1, table 1] 

and the Guadalupe Kerrville site, which were each sampled 

twice) (tables 3–6). Reasons for discrepancies in the number 

of fish and the number of species caught between 2012 and 

2013 include changes in sampling methodology. To minimize 

holding times, stress, and mortality during the transfer of fish 

to the hatchery in 2013, fish-collection activity was often 

suspended once sufficient quantities of target fish species were 

collected. Additionally, only five of the sites that were sampled 

in 2012 were resampled in 2013, so direct comparisons of fish 

abundance between 2012 and 2013 should not be made. The 

largest number of individuals (416) was collected on August 

22, 2012, from the Llano Castell site, a site that was not 

resampled in 2013. In addition, fish populations might have 

declined in the stream reaches at sites that were sampled in 

2012 and again in 2013; fish collection activities might have 

caused a reduction in the number and types of fish available 

for collection at sites resampled in 2013 relative to 2012. 

Frequency of Parasitism in Fish 

Assessed for Glochidia in Field and 

Laboratory Settings

Only a small percentage (3 percent in 2012 and 19 percent 

in 2013) of the fish that were collected over the course of the 

study was sent to the hatchery for glochidia recovery. Any 

fish that were not submitted to the hatchery were assessed for 

parasitism by glochidia in the field or in the laboratory. The 

number of parasitized fish was used as the basis for comparison 

between fish assessed for glochidia in field and laboratory 

settings rather than the number of glochidia observed because 

of concerns that glochidia could be mistaken for other types of 

parasites. There was also some concern that glochidia counts 

made on live fish in the field would be less accurate than 

assessing the presence or absence of glochidia. References to 

parasitism in fish that were assessed for glochidia in the field or 

in the laboratory will refer to instances of suspected parasitism 

by glochidia because of the potential for mistaking other types 

of parasites with glochidia. It is important to note that a fish 

parasitized with glochidia is not necessarily parasitized with 
28 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0664_fig 09

River carpsucker

Smallmouth buffalo

Gray redhorse

Redbreast sunfish

Green sunfish

Warmouth

Orangespotted sunfish

Bluegill

Longear sunfish

Redear sunfish

Spotted bass

Largemouth bass

Guadalupe bass

Rio Grande cichlid

Gizzard shad

Central stoneroller

Red shiner

Blacktail shiner

Common carp

Burrhead chub

Bullhead minnow

Blackstripe topminnow

Channel catfish

Tadpole madtom

Flathead catfish

Spotted gar

Longnose gar

Orangethroat darter

Texas logperch

Dusky darter

Western mosquitofish

Freshwater drum

Slough darter

Bigscale logperch

Fish species common name

Number of fish caught

0

50

100

150

200

250

300

EXPLANATION

 Site short name and date sampled (table 1) Family names for fish species collected 

Colorado Columbus (6/11/2013)

Guadalupe Victoria (6/10/2013)

Colorado Nada (5/2/2013)

Pedernales Fredericksburg (5/1/2013)

Guadalupe Kerrville (4/30/2013)

Guadalupe Victoria (4/4/2013)

San Antonio Charco (4/3/2013)

Guadalupe Kerrville (4/2/2013)

San Saba 208 (4/1/2013) Catostomidae

Centrarchidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

Colorado San Saba (4/29/2013)

San Saba Menard (4/5/2013)

Figure 9. Abundance of potential host fish from sites sampled in 2013 in central and southeastern Texas, 2012–13.
Frequency of Parasitism in Fish Assessed for Glochidia in Field and Laboratory Settings 29

glochidia from one of the target mussel species. In addition, 

the presence of glochidia on a fish does not necessarily 

indicate that the fish is a host because glochidia will attach 

to nonhosts. Additionally, fish that were sent to the hatchery 

for glochidia recovery were not included in any calculations 

of average total length because these fish were not measured 

prior to being sent. These measurements were not taken in 

order to maximize fish survival by minimizing handling and 

stress to the fish. 

A minimum of two fish (any species) parasitized with 

glochidia was collected from each of the 10 sites sampled 

during 2012 (table 3). The highest percentage of parasitized 

fish (19.1 percent) was measured at the Guadalupe Victoria 

site (27 instances of parasitism out of 141 fish), whereas the 

lowest percentage (1.0 percent) was measured at the Llano 

Castell site (4 instances of parasitism out of 416 fish) (fig. 

10). More than 10 percent of the fish were parasitized at three 

sites (Colorado Garwood, Guadalupe Victoria, and San Saba 

126). These three sites plot above the dashed line depicting 

the relation between the number of fish parasitized with 

glochidia by site compared to the number of fish collected by 

site in fig. 10B.

Parasitized individuals were collected from five families 

of fish in 2012 (fig. 11, table 3). The highest percentage 

of parasitized individuals (12.1 percent) was measured 

in the catfish family Ictaluridae (ictalurids), followed by 

centrarchids at 7.0 percent (fig. 11A). Centrarchids had the 

highest number of parasitized individuals (87), followed by 

cyprinids and the ictalurids (each with eight individuals) 

(fig. 11B). Each of the seven families that did not have any 

parasitized individuals was represented by 14 or fewer 

individuals from all 10 sites combined. The seven families 

of fish without any documented parasitized individuals may 

be an artifact of the small number of individuals representing 

these families that were collected during the study. Other 

factors that could have contributed to the lack of parasitism 

in these seven families include fish morphology, behavior, 

and mesohabitat preference. The two families with the 

largest average total length (Lepisosteidae and Sciaenidae) 

and the three families with the smallest average total length 

(Characidae, Fundulidae, and Poeciliidae, each of which is 

represented by a single collected species) had no parasitized 

individuals, so the size of the individual was not a consistent 

predictor of the frequency of parasitism. 

Nine sites were sampled in 2013, and 2 of the 9 sites 

(Guadalupe Victoria and Guadalupe Kerrville) were sampled 

twice (table 1). No parasitized fish were observed at 1 of 

the 9 sites sampled in 2013 (San Saba Menard), and no 

parasitized fish were recorded at another site (Guadalupe 

Victoria) the second time it was sampled on June 10, 2013 

(fig. 12, table 5). The highest percentage of parasitized fish 

(22.7 percent) was recorded at the Pedernales Fredericksburg 

site (10 instances of parasitism out of 44 fish), followed by 

the Guadalupe Victoria site on April 4, 2013, at 13.5 percent 

(22 instances of parasitism out of 163 fish) and the San Saba 

208 site on April 1, 2013, at 13.0 percent (7 instances of 

parasitism out of 54 fish) (fig. 12, table 5). The percentage 

of parasitized fish increased substantially at the Pedernales 

Fredericksburg site between 2012 (1.4 percent) and 2013 (22.7 

percent), likely because the sampled area was upstream from 

the bridge at this site in 2013, whereas it was downstream 

from the bridge in 2012 (table 1). The area that was sampled 

upstream from the bridge was wider than the downstream 

area, and it included runs and pools more than 2 feet deep, 

which provide better habitat for larger fish (average total 

lengths increased from 98 mm in 2012 to 158 mm in 2013). 

Three sites (Pedernales Fredericksburg, San Saba 208, and 

Guadalupe Victoria) plot above the dashed line in figure 12B

used to identify sites where more than 10 percent of fish were 

parasitized with glochidia.

Parasitized individuals were only collected from 

three families of fish in 2013 (fig. 13, table 5). Ictalurids 

exhibited the highest frequency of parasitism (26.5 percent), 

followed by centrarchids at 7.1 percent. Centrarchids had 

the highest number of parasitized individuals (40), followed 

by ictalurids (13). Of the eight families that did not have 

any parasitized individuals, it is possible that insufficient 

numbers of individuals were collected to accurately assess 

the frequency of parasitism. For example, at most only 25 

individuals were collected representing each of these eight 

families from all nine sites combined. Although collecting 

large sample sizes can put additional survival stress on species 

that are not common, there is some evidence underscoring 

the importance of large sample sizes in determining a 

representative proportion of parasitized individuals in a 

family. Members of the two families that were collected 

most frequently, centrarchids (1,247 individuals in 2012 and 

564 individuals in 2013) and cyprinids (581 individuals in 

2012 and 654 individuals in 2013), were parasitized in almost 

the same percentages in 2012 and 2013. In 2012, 7.0 percent 

of centrarchids and 1.4 percent of cyprinids were parasitized, 

whereas in 2013, 7.1 percent of centrarchids were parasitized 

and 1.1 percent of cyprinids were parasitized.

Of the fish that were not sent to the hatchery but 

assessed for glochidia in the field or in the laboratory, at least 

13 species were parasitized in 2012; this does not include two 

parasitized individuals of the genus Micropterus that were 

collected at the Guadalupe Victoria site whose species could 

not be identified because they were too small and immature 

(fig. 14, table 3). Five of the 13 species of parasitized fish 

identified in 2012 were centrarchids, and 3 were cyprinids. 

Other than the unknown Micropterus genus individuals, the 

longear sunfish was the species with the highest percentage 

of parasitized individuals in 2012 (17.3 percent; 36 of 208 

individuals), followed by bullhead minnow (14.3 percent; 

4 of 28 individuals) and channel catfish (13.0 percent; 7 of 

54 individuals). Of the fish that were not sent to the hatchery 

but assessed for glochidia in the field or in the laboratory, 
30 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0664_fig10 Number of fish parasitized with glochidia by site

0

5

10

15

20

25

30

Number of fish collected by site

0 100 200 300 400 500

B.

A. Percentage of fish caught

that were parasitized

Guadalupe Victoria

19.1

Colorado Garwood

11.6

San Saba Menard

2.7

San Saba 208

6.4

San Saba 126

13.1

Guadalupe Kerrville

3.2

San Marcos

Palmetto

6.8

Pedernales Fredericksburg

Llano Junction 1.4

4.0 Llano Castell

1.0

EXPLANATION

10 percent of fish parasitized 

Site short name (table 1) 

 Colorado Garwood

 Guadalupe Victoria

 Guadalupe Kerrville

 Llano Castell

 Llano Junction

 Pedernales Fredericksburg

 San Marcos Palmetto

 San Saba 126

 San Saba 208

 San Saba Menard

Figure 10. A, percentage, and B, number of parasitized fish that were assessed in the field or laboratory for glochidia at 10 sites in 2012 

as part of a mussel host-fish study, central and southeastern Texas, 2012–13.

only eight species were parasitized in 2013. Four of the 

eight species of parasitized fish were centrarchids, two were 

cyprinids, and two were ictalurids. Flathead catfish (Pylodictis 

olivaris) was the species with the highest percentage of 

parasitized individuals in 2013 (42.9 percent), although 

sample size was small (3 parasitized individuals out of 7). 

Channel catfish was the second most parasitized species 

in 2013 (24.4 percent) (10 of 41 individuals), followed by 

longear sunfish (11.6 percent) (25 of 216 individuals) and 

redbreast sunfish (9.1 percent) (13 of 143 individuals) (table 

5). The number of parasitized species based on field and 

laboratory observations was lower in 2013 than in 2012, likely 

because more fish were sent to the hatchery in 2013 (321) than 

in 2012 (75). In many cases in 2013, all of the individuals of 

a given species that were collected at a site were submitted to 

the hatchery. When data from the hatchery are included, the 

total number of parasitized species in 2013 (16) surpasses the 

number of parasitized species collected in 2012 (likely 13 but 

could be as many as 15 depending on the species of the two 

unknown parasitized individuals of Micropterus genus).
Frequency of Parasitism in Fish Assessed for Glochidia in Field and Laboratory Settings 31

laf14-0664_fig11 Average total length, in millimeters

0

100

200

300

400

500

Number of fish parasitized with

glochidia by family

0

10

20

30

40

50

60

70

80

90

100

Catostomidae

Characidae

Centrarchidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

Family

Number of fish collected by family

0 200 400 600 800 1,000 1,200 1,400

Percidae

2.0

Catostomidae

3.7

Centrarchidae

7.0

Cyprinidae

1.4

Ictaluridae

12.1

A. Percentage of fish caught

that were parasitized

B.

C.

Catostomidae

Centrarchidae

Characidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

Family

EXPLANATION

Figure 11. A, percentage; B, number; and C, total length of fish grouped by family that were assessed in the field or laboratory for 

glochidia in 2012 as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
32 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0664_fig12 Number of fish parasitized with glochidia by site

0

5

10

15

20

25

Number of fish collected by site

0 100 200 300 400

B.

Guadalupe Victoria (6/10/2013) 0.0 - not shown

San Saba Menard 0.0 - not shown

A. Percentage of fish caught

that were parasitized

Guadalupe

Victoria

(4/4/2013) 

13.5

San Saba 208

13.0

San Antonio Charco

3.7

Pedernales Fredericksburg

22.7

Colorado Columbus

0.5

Colorado Nada

3.7

Colorado San Saba

4.0

Guadalupe Kerrville (4/2/2013)

2.0

Guadalupe Kerrville (4/30/2013)

1.7

EXPLANATION

10 percent of fish parasitized 

Site short name (table 1) 

 Colorado San Saba

 Colorado Nada

 Colorado Columbus

 Guadalupe Victoria (4/4/2013)

 Guadalupe Victoria (6/10/2013)

 Guadalupe Kerrville (4/2/2013)

 Guadalupe Kerrville (4/30/2013)

 Pedernales Fredericksburg

 San Antonio Charco

 San Saba 208

 San Saba Menard

Figure 12. A, percentage, and B, number of parasitized fish that were assessed in the field or laboratory for glochidia at nine sites 

(two of which were sampled twice) in 2013 as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Species Species common name

Short name (fig. 1) with sampling date in parenthe

San Saba 208 (4/1) Guadalupe Kerrville (4/2) 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. 

fis

Catostomidae Carpiodes carpio River carpsucker

Ictiobus bubalus Smallmouth buffaloMoxostoma congestum Gray redhorse 1 430 0

Centrarchidae Lepomis auritus Redbreast sunfish 68 111 3 

Lepomis cyanellus Green sunfish 3 97 0 9 97 0 

Lepomis gulosus Warmouth 

Lepomis humilis Orangespotted sunfishLepomis macrochirus Bluegill 21 74 0 

Lepomis megalotis Longear sunfish 21 68 7 3Lepomis microlophus Redear sunfish 4 133 0Micropterus 

punctulatus

Spotted bass 3 115 0 

Micropterus salmoides Largemouth bass 3 93 0 11 154 0 

Micropterus treculii Guadalupe bass

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid 

Clupeidae Dorosoma cepedianum Gizzard shad

Cyprinidae Campostoma 

anomalum

Central stoneroller 4 81 0

Cyprinella lutrensis Red shiner 5Cyprinella venusta Blacktail shiner 19 83 0 13 78 0Cyprinus carpio Common carpMacrhybopsis marconis Burrhead chubPimephales vigilax Bullhead minnow 4 43 0 17 56 0 5

Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Species Species common name Short name (fig. 1) with sampling date in parenthe

San Saba 208 (4/1) Guadalupe Kerrville (4/2) 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations No. 

fis

Fundulidae Fundulus notatus Blackstripe topminnow 2 60 0 Ictaluridae Ictalurus punctatus Channel catfish 1

Noturus gyrinus Tadpole madtom 

Pylodictis olivaris Flathead catfish 

Lepisosteidae Lepisosteus oculatus Spotted gar Lepisosteus osseus Longnose gar Percidae Etheostoma spectabile Orangethroat darter Percina carbonaria Texas logperch 2 48 0 

Percina sciera Dusky darter Poeciliidae Gambusia affinis Western mosquitofish 1

Sciaenidae Aplodinotus grunniens Freshwater drumTotals 54 73 7 151 101 3 19

Percentage of fish infested with glochidia 13.0 2.0 

Total number of species collected (includes fish from table 6) 11 12 

Species not shown in this table but included in table 6 Gray redhorse Channel catfish Bluegill Orangethroat darter Red shiner Bigscale logperch
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Species Species common name

Short name (fig. 1) with sampling date in parenthe

Guadalupe Victoria (4/4) San Saba Menard (4/5) 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No

fis

Catostomidae Carpiodes carpio River carpsucker

Ictiobus bubalus Smallmouth buffalo 1 480 0

Moxostoma congestum Gray redhorse

Centrarchidae Lepomis auritus Redbreast sunfish 13 130 0

Lepomis cyanellus Green sunfish 1 100 0 2 98 0Lepomis gulosus WarmouthLepomis humilis Orangespotted 

sunfish

Lepomis macrochirus Bluegill 1 90 0 1 55 0 1

Lepomis megalotis Longear sunfish 33 95 16 3

Lepomis microlophus Redear sunfishMicropterus 

punctulatus

Spotted bass 11 165 1

Micropterus salmoides Largemouth bassMicropterus treculii Guadalupe bass

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid

Clupeidae Dorosoma cepedianum Gizzard shad

Cyprinidae Campostoma 

anomalum

Central 

stoneroller

Cyprinella lutrensis Red shiner 82 61 4 2

Cyprinella venusta Blacktail shiner 2

Cyprinus carpio Common carpMacrhybopsis marconis Burrhead chub 8 60 0

Pimephales vigilax Bullhead minnow 20 61 0 1

Fundulidae Fundulus notatus Blackstripe 

topminnow
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Species Species common name Short name (fig. 1) with sampling date in parenthe

Guadalupe Victoria (4/4) San Saba Menard (4/5) 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations No. 

fis

Ictaluridae Ictalurus punctatus Channel catfish 3 340 1 1

Noturus gyrinus Tadpole madtom Pylodictis olivaris Flathead catfish 

Lepisosteidae Lepisosteus oculatus Spotted gar Lepisosteus osseus Longnose gar Percidae Etheostoma spectabile Orangethroat darter Percina carbonaria Texas logperch 2 60 0 Percina sciera Dusky darter Poeciliidae Gambusia affinis Western mosquitofish 1 35 0 Sciaenidae Aplodinotus grunniens Freshwater drum 

Totals 163 83 22 16 121 0 12

Percentage of fish infested with glochidia 13.5 0.0 

Total number of species collected (includes fish from table 6) 13 6 

Species not shown in this table but included in table 6 Spotted gar Spotted bass 

Slough darter Central stoneroller 

Orangethroat darter 
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Species Species common name

Short name (fig. 1) with sampling date in parenth

Guadalupe Kerrville (4/30) Pedernales Fredericksburg (5/1) 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

No. 

fis

Catostomidae Carpiodes carpio River carpsucker 1

Ictiobus bubalus Smallmouth buffaloMoxostoma congestum Gray redhorse 2 428 0

Centrarchidae Lepomis auritus Redbreast sunfish 26 130 0 31 159 10

Lepomis cyanellus Green sunfish 1 85 0 

Lepomis gulosus Warmouth 6 183 0

Lepomis humilis Orangespotted sunfish 

Lepomis macrochirus Bluegill 17 97 0

Lepomis megalotis Longear sunfish 9 137 0 

Lepomis microlophus Redear sunfishMicropterus 

punctulatus

Spotted bass 4 111 0 

Micropterus salmoides Largemouth bass 5 247 0 4 196 0 Micropterus treculii Guadalupe bass 7 259 0

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid

Clupeidae Dorosoma cepedianum Gizzard shadCyprinidae Campostoma 

anomalum

Central stoneroller 5 108 0

Cyprinella lutrensis Red shiner 2

Cyprinella venusta Blacktail shiner 21 79 0 

Cyprinus carpio Common carpMacrhybopsis 

marconis

Burrhead chub

Pimephales vigilax Bullhead minnow 

Fundulidae Fundulus notatus Blackstripe topminnowIctaluridae Ictalurus punctatus Channel catfish 8 204 2 
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Species Species common name Short name (fig. 1) with sampling date in parenth

Guadalupe Kerrville (4/30) Pedernales Fredericksburg (5/1) 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. total length (mm) No. of glochidia infestations No. 

fis

Noturus gyrinus Tadpole madtom Pylodictis olivaris Flathead catfish Lepisosteidae Lepisosteus oculatus Spotted gar Lepisosteus osseus Longnose gar 

Percidae Etheostoma spectabile Orangethroat darter 13 43 0 Percina carbonaria Texas logperch 4 119 0 Percina sciera Dusky darter Poeciliidae Gambusia affinis Western mosquitofish Sciaenidae Aplodinotus grunniens Freshwater drum Totals 119 130 2 44 158 10 5

Percentage of fish infested with glochidia 1.7 22.7 

Total number of species collected (includes fish from table 6) 13 5 

Species not shown in this table but included in table 6 Bluegill 

Texas logperch
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Species Species common name

Short name (fig. 1) with sampling date in parent

Guadalupe Victoria (6/10) Colorado 

No. of 

fish

Avg. total 

length 

(mm)

No. of glochidia 

infestations

No. of 

fish

Avg. to

lengt

(mm

Catostomidae Carpiodes carpio River carpsucker

Ictiobus bubalus Smallmouth buffaloMoxostoma congestum Gray redhorse 3 290 

Centrarchidae Lepomis auritus Redbreast sunfish

Lepomis cyanellus Green sunfish 3 113 

Lepomis gulosus Warmouth

Lepomis humilis Orangespotted sunfish 8 89 

Lepomis macrochirus Bluegill 2 90 Lepomis megalotis Longear sunfish 24 89 0 53 85 

Lepomis microlophus Redear sunfishMicropterus punctulatus Spotted bass 13 117 Micropterus salmoides Largemouth bass 31 68 Micropterus treculii Guadalupe bass 4 196 0

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid 3 98 0 1 70 

Clupeidae Dorosoma cepedianum Gizzard shad 1 220 

Cyprinidae Campostoma anomalum Central stoneroller 1 70 

Cyprinella lutrensis Red shiner 9 51 0 57 48 

Cyprinella venusta Blacktail shiner 172 65 Cyprinus carpio Common carp 2 403 Macrhybopsis marconis Burrhead chub 3 60 0

Pimephales vigilax Bullhead minnow 11 49 0 15 51 

Fundulidae Fundulus notatus Blackstripe topminnow 2 55 

Ictaluridae Ictalurus punctatus Channel catfish 4 483 

Noturus gyrinus Tadpole madtomPylodictis olivaris Flathead catfish
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Species Species common name Short name (fig. 1) with sampling date in parent

Guadalupe Victoria (6/10) Colorado 

No. of fish Avg. total length (mm) No. of glochidia infestations No. of fish Avg. to

lengt

(mm

Lepisosteidae Lepisosteus oculatus Spotted gar 1 540 

Lepisosteus osseus Longnose gar Percidae Etheostoma spectabile Orangethroat darter Percina carbonaria Texas logperch 1 100 0 Percina sciera Dusky darter 2 43 0 Poeciliidae Gambusia affinis Western mosquitofish 1 30 

Sciaenidae Aplodinotus grunniens Freshwater drum Totals 57 80 0 370 78 

Percentage of fish infested with glochidia 0.0 

Total number of species collected (includes fish from table 6) 11 

Species not shown in this table but included in table 6 Largemouth bass Flathead c

Channel catfish Slough darter
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued[No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected]

Family Species Species common name

Short name (fig. 1) with sampling date in parenth

Total - all sites (2013 only) Totals - by 

No. of 

fish

Avg. total 

length 

(mm)

No. of 

glochidia 

infestations

Percentage 

of fish 

infested

No. of 

fish

Avg. total 

length 

(mm)

Catostomidae Carpiodes carpio River carpsucker 12 201 0 0.0

19 266 

Ictiobus bubalus Smallmouth buffalo 1 480 0 0.0

Moxostoma 

congestum

Gray redhorse 6 359 0 0.0

Centrarchidae Lepomis auritus Redbreast sunfish 143 125 13 9.1

564 108 

Lepomis cyanellus Green sunfish 23 94 0 0.0

Lepomis gulosus Warmouth 7 166 0 0.0

Lepomis humilis Orangespotted sunfish 9 91 0 0.0

Lepomis macrochirus Bluegill 58 83 0 0.0

Lepomis megalotis Longear sunfish 216 89 25 11.6

Lepomis microlophus Redear sunfish 4 133 0 0.0

Micropterus 

punctulatus

Spotted bass 33 141 1 3.0

Micropterus 

salmoides

Largemouth bass 60 116 1 1.7

Micropterus treculii Guadalupe bass 11 236 0 0.0

Cichlidae Herichthys 

cyanoguttatum

Rio Grande cichlid 12 70 0 0.0 12 70 

Clupeidae Dorosoma 

cepedianum

Gizzard shad 1 220 0 0.0 1 220 

Cyprinidae Campostoma 

anomalum

Central stoneroller 11 91 0 0.0

654 62 

Cyprinella lutrensis Red shiner 247 55 6 2.4

Cyprinella venusta Blacktail shiner 253 70 1 0.4

Cyprinus carpio Common carp 2 403 0 0.0

Macrhybopsis 

marconis

Burrhead chub 11 60 0 0.0

Pimephales vigilax Bullhead minnow 130 54 0 0.0
Table 5. Number of fish collected and glochidial parasitism by species from sites sampled in 2013 as part of a mussel host-fish study, central and so13.—Continued [No., number; Avg., average; mm, millimeters; shading indicates fish species are members of the same family; cross-hatching indicates fish species were not collected] Family Species Species common name Short name (fig. 1) with sampling date in parenth

Total - all sites (2013 only) Totals - by 

No. of fish Avg. total length (mm) No. of glochidia infestations Percentage of fish infested No. of fish Avg. total length (mm) 

Fundulidae Fundulus notatus Blackstripe topminnow 4 58 0 0.0 4 58 

Ictaluridae Ictalurus punctatus Channel catfish 41 240 10 24.4 Noturus gyrinus Tadpole madtom 1 65 0 0.0 49 221 

Pylodictis olivaris Flathead catfish 7 131 3 42.9 Lepisosteidae Lepisosteus oculatus Spotted gar 1 540 0 0.0 2 555 

Lepisosteus osseus Longnose gar 1 570 0 0.0 Percidae Etheostoma spectabile Orangethroat darter 13 43 0 0.0 25 60 

Percina carbonaria Texas logperch 10 85 0 0.0 Percina sciera Dusky darter 2 43 0 0.0 Poeciliidae Gambusia affinis Western mosquitofish 12 40 0 0.0 12 40 

Sciaenidae Aplodinotus grunniens Freshwater drum 2 313 0 0.0 2 313 

Totals 1,344 91 60 4.5 1,344 91 
Frequency of Parasitism in Fish Assessed for Glochidia in Field and Laboratory Settings 43

laf14-0664_fig13

0

100

200

300

400

500

600

Average total length, in millimeters

0

5

10

15

20

25

30

35

40

45

50

Number of fish parasitized with

glochidia by family

Catostomidae

Centrarchidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

Family

Number of fish collected by family

0 100 200 300 400 500 600 700

Centrarchidae

7.1

Cyprinidae

1.1

Ictaluridae

26.5

B.

C.

A. Percentage of fish caught

that were parasitized

Catostomidae

Centrarchidae

Cichlidae

Clupeidae

Cyprinidae

Fundulidae

Ictaluridae

Lepisosteidae

Sciaenidae

Percidae

Poeciliidae

Family

EXPLANATION

Figure 13. A, percentage; B, number; and C, average total length of fish grouped by family that were assessed in the field or laboratory 

for glochidia in 2013 as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
44 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0664_fig14

Fish species common name

Blacktail shiner

Red shiner

Redbreast sunfish

Spotted bass

Flathead catfish

Largemouth bass

Longear sunfish

Channel catfish

Fish species common name

Blacktail shiner

Red shiner

Texas logperch

Redbreast sunfish

Spotted bass

Gray redhorse

Flathead catfish

Largemouth bass

Dusky darter

Bullhead minnow

Bluegill

Channel catfish

Unknown member of 

Micropterus genus

Longear sunfish

0

5

10

15

20

25

Percentage of parasitized fish

0

5

10

15

20

25

Percentage of parasitized fish

30

35

40

45

250

300

200

100

0

Average total length, in millimeters, of parasitized fish

150

50

400

300

200

100

0

Average total length, in millimeters,

of parasitized fish

EXPLANATION

Average total length, in millimeters, 

 of infested fish

Percentage of fish caught that were 

 parasitized

A. 2012

B. 2013

Figure 14. Percentage of parasitized fish and average total length of fish grouped by species that were assessed in the field or 

laboratory for glochidia in A, 2012; and B, 2013; as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
Frequency of Juvenile Mussels or Glochidia Recovered from Hatchery-Held Fish 45

Frequency of Juvenile Mussels or 

Glochidia Recovered from HatcheryHeld Fish

Multiple individuals of the same fish species were 

frequently placed in a single holding tank at the hatchery. 

In these cases, attributing juvenile mussels or glochidia to 

specific individuals and quantifying how many juvenile 

mussels or glochidia were recovered from each individual 

fish was not possible; therefore, parasitism in fish held at 

the hatchery is discussed as the average number of juvenile 

mussels or glochidia by fish species. As described in the 

“Methods” section of this report, juvenile mussels and 

glochidia were not differentiated in hatchery-held fish; 

therefore, when discussing study results pertaining to fish held 

at the hatchery, juvenile mussels and glochidia are hereinafter 

collectively referred to as “juvenile mussels.” Because 

glochidia observed in the USGS laboratory on fish returned 

by the hatchery remained attached to the gills following the 

28-day trials, these glochidia are referred to as “glochidia” 

rather than juvenile mussels. References to parasitism in 

fish that released juvenile mussels that were recovered at 

the hatchery refer to actual parasitism, whereas references 

to parasitism in fish that were returned by the hatchery 

and assessed for glochidia in the USGS laboratory refer to 

suspected parasitism.

In 2012, fish were only submitted to the hatchery from 

the Pedernales Fredericksburg site on August 23 and the 

San Marcos Palmetto site on August 24 (table 4). Of the six 

species collected at the Pedernales Fredericksburg site that 

were submitted to the hatchery, only red shiners and blacktail 

shiners released any juvenile mussels; the red shiners (n=12) 

released 2 juvenile mussels, and the blacktail shiners (n=10) 

released 1 juvenile mussel (table 4). Of the five species 

submitted to the hatchery that were collected at the San 

Marcos Palmetto site, all except for the dusky darters (Percina 

sciera) released juvenile mussels. The longear sunfish (n=6) 

and the blacktail shiners (n=10) released one juvenile mussel 

apiece. The largemouth bass (n=6) released 2 juvenile mussels, 

and the red shiners (n=10) released 4 juvenile mussels.

With the exception of the San Antonio Charco site, 

fish were submitted to the hatchery from all sampling sites 

in 2013, including fish from both sample collection dates at 

the Guadalupe Victoria and Guadalupe Kerrville sites. Fish 

collected on April 3, 2013, from the San Antonio Charco 

site were not submitted to the hatchery because of a lack of 

available holding tanks at that time; fish collected in early 

April 2013 at sites which had previously been sampled in 

2012 (the Guadalupe Victoria, Guadalupe Kerrville, San Saba 

208, and San Saba Menard sites) were given priority. The 

average number of juvenile mussels or glochidia per fish is 

presented by species in figures 15 and 16 as the sum of the 

proportion of juvenile mussels per fish by species recovered at 

the hatchery and the proportion of glochidia per fish extracted 

in the laboratory from fish returned by the hatchery. In most 

cases, the proportion of juvenile mussels recovered at the 

hatchery represented the majority of the average number of 

juvenile mussels or glochidia per fish by species depicted in 

figures 15 and 16.

During the first sampling period in 2013 (April 1–5), 

slightly more than half (16 out of 29) of the fish species (on 

a per site basis) that were submitted to the hatchery released 

juvenile mussels, and individuals from 5 of the 16 fish species 

retained glochidia after completing trials at the hatchery (fig. 

15). The most species that released juvenile mussels (7 out of 

8 species) were collected at the Guadalupe Victoria site. There 

were at least two species that released juvenile mussels that 

were collected at each of the remaining three sites sampled 

during the first sampling period in 2013. Largemouth bass 

collected from the Guadalupe Kerrville site and spotted bass 

(Micropterus punctulatus) collected from the Guadalupe 

Victoria site released more than four juvenile mussels per 

individual on average.

Compared to the other sampling periods in 2013, 

substantially fewer glochidia per fish were present on fish 

submitted to the hatchery during the second sampling period 

in 2013 (April 29–May 2). Only longear sunfish (collected at 

the Colorado San Saba site) averaged more than one juvenile 

mussel per fish (fig. 15). Less than a third (7 out of 25) of the 

fish species (on a per site basis) released juvenile mussels that 

were recovered at the hatchery; individuals from 3 of these 

7 fish species retained glochidia after completing trials at 

the hatchery. One largemouth bass collected at the Colorado 

Nada site retained a single glochidium that was not recovered 

at the hatchery. None of the fish collected at the Pedernales 

Fredericksburg and Colorado Nada sites released juvenile 

mussels at the hatchery.

Although only two sites were sampled during the third 

sampling period in 2013 (June 10–11), more juvenile mussels 

were recovered at the hatchery during this sampling period 

(107) than were recovered during the first two sampling 

periods in 2013 combined (102) (table 6). Four out of six 

fish species (from the two sites) that were submitted to the 

hatchery released juvenile mussels, and individuals from 2 

of the 4 fish species retained glochidia after completing trials 

at the hatchery (fig. 15). An average of 17 juvenile mussels 

was recovered per largemouth bass submitted to the hatchery 

from the Guadalupe Victoria site during the third sampling 

period (fig. 15) on June 10, 2013, and the 14 fish (representing 

4 species) submitted from the Guadalupe Victoria site on that 

date released a total of 102 juvenile mussels at the hatchery for 

an average of 7.3 juvenile mussels per fish (table 6).

A total of 19 fish species collected at nine sites (including 

both 2013 sampling periods at Guadalupe Victoria and 

Guadalupe Kerrville) was submitted to the hatchery in 2013, 

and 14 of these species released juvenile mussels that were 

recovered at the hatchery (fig. 16A). The three most productive 

species, in terms of average juvenile mussels recovered, 

were longear sunfish, largemouth bass, and spotted bass, 

each of which averaged more than two glochidia recovered 

per individual. Centrarchids released the highest number of 
46 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

laf14-0664_fig15

MOXCON

LEPMAC

MICSAL

CYPLUT

CYPVEN

PIMVIG

PERMAC

LEPAUR

LEPMAC

MICSAL

CYPVEN

CAMANO

PIMVIG

ICTPUN

ETHSPE

LEPMEG

MICPUN

CYPLUT

MACMAR

PIMVIG

ICTPUN

LEPOCU

ETHGRA

LEPAUR

LEPMAC

MICPUN

CAMANO

LEPCYA

ETHSPE

MOXCON

LEPMAC

LEPMEG

MICSAL

CYPVEN

CAMANO

PIMVIG

ICTPUN

PERMAC

MOXCON

LEPAUR

LEPMAC

MICSAL

ICTPUN

PERCAR

LEPAUR

LEPMAC

MICSAL

PERCAR

LEPMAC

LEPMEG

MICSAL

CYPVEN

PIMVIG

ICTPUN

LEPMEG

MICSAL

ICTPUN

ETHGRA

LEPMEG

MICSAL

CYPVEN

PYLOLI

Fish species abbreviation

Fish species abbreviation

Fish species abbreviation

0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

10

Average number of juveniles

or glochidia per fish

Average number of juveniles

or glochidia per fish

Average number of juveniles

or glochidia per fish

MOXCON Gray redhorse

LEPAUR Redbreast sunfish

LEPMAC Bluegill

LEPMEG Longear sunfish

MICPUN Spotted bass

MICSAL Largemouth bass

CYPLUT Red shiner

CYPVEN Blacktail shiner

MACMAR Burrhead chub

CAMANO Central stoneroller

PIMVIG Bullhead minnow

ICTPUN Channel catfish

PYLOLI Flathead catfish

ETHGRA Slough darter

ETHSPE Orangethroat darter

PERCAR Texas logperch

LEPOCU Spotted gar

PERMAC Bigscale logperch

Fish species common name

LEPCYA Green sunfish

EXPLANATION

Proportion of glochidia extracted 

 in USGS laboratory from fish

 returned by the USFWS

 San Marcos National Fish

 Hatchery and Technology

 Center

Proportion of glochidia or juveniles

 recovered at the USFWS San

 Marcos National Fish Hatchery

 and Technology Center

Average number of glochidia or

 juveniles per fish

U.S. Geological Survey

U.S. Fish and Wildlife Service

USGS

USFWS

(17)

Zero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero value

Zero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero valueZero value

(17)

Zero valueZero valueZero value

A. First sampling period (4/1/2013–4/5/2013)

B. Second sampling period (4/29/2013–5/2/2013)

C. Third sampling period 

(6/10/2013–6/11/2013)

Guadalupe Victoria

Colorado

Columbus

San Saba 208 Guadalupe Kerrville Guadalupe Victoria San Saba Menard

Colorado San Saba Guadalupe Kerrville Pedernales Colorado Nada

Fredericksburg

Figure 15. Average number of juvenile mussels or glochidia collected per fish species by site from fish held at the U.S. Fish and 

Wildlife Service San Marcos National Fish Hatchery and Technology Center in 2013 (A, First sampling period; B, second sampling period; 

and C, third sampling period), as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
Frequency of Juvenile Mussels or Glochidia Recovered from Hatchery-Held Fish 47

Table 6. Juvenile mussels or glochidia recovered from hatchery-held fish collected in 2013 in central and southeastern Texas and 

submitted to U.S. Fish and Wildlife Service National Fish Hatchery and Technology Center in San Marcos, Tex., as part of a mussel hostfish study, 2012–13.—Continued

Short name Date Family Species 

common name

Number 

of fish 

submitted 

to hatchery

Number of 

juvenile mussels 

or glochidia 

recovered 

from hatcheryheld fish

Number of 

juvenile mussels or 

glochidia collected 

in laboratory from 

fish returned by 

the hatchery

San Saba 208 4/1/2013 Catostomidae Gray redhorse 1 0 0

San Saba 208 4/1/2013 Centrarchidae Bluegill 6 0 0

San Saba 208 4/1/2013 Centrarchidae Largemouth bass 3 1 6

San Saba 208 4/1/2013 Cyprinidae Red shiner 6 0 0

San Saba 208 4/1/2013 Cyprinidae Blacktail shiner 3 0 0

San Saba 208 4/1/2013 Cyprinidae Bullhead minnow 5 1 3

San Saba 208 4/1/2013 Percidae Bigscale logperch 5 0 0

Guadalupe Kerrville 4/2/2013 Centrarchidae Redbreast sunfish 2 2 0

Guadalupe Kerrville 4/2/2013 Centrarchidae Bluegill 5 3 0

Guadalupe Kerrville 4/2/2013 Centrarchidae Largemouth bass 3 13 3

Guadalupe Kerrville 4/2/2013 Cyprinidae Central stoneroller 6 0 0

Guadalupe Kerrville 4/2/2013 Cyprinidae Blacktail shiner 9 0 0

Guadalupe Kerrville 4/2/2013 Cyprinidae Bullhead minnow 10 0 0

Guadalupe Kerrville 4/2/2013 Ictaluridae Channel catfish 3 0 0

Guadalupe Kerrville 4/2/2013 Percidae Orangethroat darter 9 1 0

Guadalupe Victoria 4/4/2013 Centrarchidae Longear sunfish 5 17 5

Guadalupe Victoria 4/4/2013 Centrarchidae Spotted bass 3 17 1

Guadalupe Victoria 4/4/2013 Cyprinidae Red shiner 10 3 0

Guadalupe Victoria 4/4/2013 Cyprinidae Burrhead chub 10 3 0

Guadalupe Victoria 4/4/2013 Cyprinidae Bullhead minnow 10 1 0

Guadalupe Victoria 4/4/2013 Ictaluridae Channel catfish 7 8 0

Guadalupe Victoria 4/4/2013 Lepisosteidae Spotted gar 1 0 0

Guadalupe Victoria 4/4/2013 Percidae Slough darter 9 3 0

San Saba Menard 4/5/2013 Centrarchidae Redbreast sunfish 10 4 0

San Saba Menard 4/5/2013 Centrarchidae Green sunfish 7 3 0

San Saba Menard 4/5/2013 Centrarchidae Bluegill 3 4 0

San Saba Menard 4/5/2013 Centrarchidae Spotted bass 5 0 0

San Saba Menard 4/5/2013 Cyprinidae Central stoneroller 3 0 0

San Saba Menard 4/5/2013 Percidae Orangethroat darter 9 0 0

Totals (first sampling period) 168 84 18

Table 6. Juvenile mussels or glochidia recovered from hatchery-held fish collected in 2013 in central and southeastern Texas and 

submitted to U.S. Fish and Wildlife Service National Fish Hatchery and Technology Center in San Marcos, Tex., as part of a mussel hostfish study, 2012–13.
48 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

Table 6. Juvenile mussels or glochidia recovered from hatchery-held fish collected in 2013 in central and southeastern Texas and 

submitted to U.S. Fish and Wildlife Service National Fish Hatchery and Technology Center in San Marcos, Tex., as part of a mussel hostfish study, 2012–13.—Continued

Short name Date Family Species 

common name

Number 

of fish 

submitted 

to hatchery

Number of 

juvenile mussels 

or glochidia 

recovered 

from hatcheryheld fish

Number of 

juvenile mussels or 

glochidia collected 

in laboratory from 

fish returned by 

the hatchery

Colorado San Saba 4/29/2013 Catostomidae Gray redhorse 4 0 0

Colorado San Saba 4/29/2013 Centrarchidae Bluegill 6 2 2

Colorado San Saba 4/29/2013 Centrarchidae Longear sunfish 6 1 7

Colorado San Saba 4/29/2013 Centrarchidae Largemouth bass 5 2 2

Colorado San Saba 4/29/2013 Cyprinidae Central stoneroller 3 0 0

Colorado San Saba 4/29/2013 Cyprinidae Blacktail shiner 12 0 0

Colorado San Saba 4/29/2013 Cyprinidae Bullhead minnow 7 1 0

Colorado San Saba 4/29/2013 Ictaluridae Channel catfish 10 9 0

Colorado San Saba 4/29/2013 Percidae Bigscale logperch 8 1 0

Guadalupe Kerrville 4/30/2013 Catostomidae Gray redhorse 3 0 0

Guadalupe Kerrville 4/30/2013 Centrarchidae Redbreast sunfish 5 0 0

Guadalupe Kerrville 4/30/2013 Centrarchidae Bluegill 5 0 0

Guadalupe Kerrville 4/30/2013 Centrarchidae Largemouth bass 5 0 0

Guadalupe Kerrville 4/30/2013 Ictaluridae Channel catfish 5 1 0

Guadalupe Kerrville 4/30/2013 Percidae Texas logperch 5 1 0

Pedernales Fredericksburg 5/1/2013 Centrarchidae Redbreast sunfish 5 0 0

Pedernales Fredericksburg 5/1/2013 Centrarchidae Bluegill 5 0 0

Pedernales Fredericksburg 5/1/2013 Centrarchidae Largemouth bass 5 0 0

Pedernales Fredericksburg 5/1/2013 Percidae Texas logperch 1 0 0

Colorado Nada 5/2/2013 Centrarchidae Bluegill 3 0 0

Colorado Nada 5/2/2013 Centrarchidae Longear sunfish 5 0 0

Colorado Nada 5/2/2013 Centrarchidae Largemouth bass 3 0 1

Colorado Nada 5/2/2013 Cyprinidae Blacktail shiner 5 0 0

Colorado Nada 5/2/2013 Cyprinidae Bullhead minnow 5 0 0

Colorado Nada 5/2/2013 Ictaluridae Channel catfish 1 0 0

Totals (second sampling period) 127 18 12

Guadalupe Victoria 6/10/2013 Centrarchidae Longear sunfish 3 27 1

Guadalupe Victoria 6/10/2013 Centrarchidae Largemouth bass 3 51 0

Guadalupe Victoria 6/10/2013 Ictaluridae Channel catfish 3 15 6

Guadalupe Victoria 6/10/2013 Percidae Slough darter 5 9 0

Colorado Columbus 6/11/2013 Centrarchidae Longear sunfish 3 5 0

Colorado Columbus 6/11/2013 Centrarchidae Largemouth bass 3 0 0

Colorado Columbus 6/11/2013 Cyprinidae Blacktail shiner 5 0 0

Colorado Columbus 6/11/2013 Ictaluridae Flathead catfish 1 0 0

Totals (third sampling period) 26 107 7

Totals (all sampling periods) 321 209 37
Frequency of Juvenile Mussels or Glochidia Recovered from Hatchery-Held Fish 49

laf14-0664_fig16

Gray redhorse

Redbreast sunfish

Bluegill

Longear sunfish

Spotted bass

Largemouth bass

Red shiner

Blacktail shiner

Burrhead chub

Central stoneroller

Bullhead minnow

Channel catfish

Flathead catfish

Slough darter

Orangethroat darter

Texas logperch

Spotted gar

Bigscale logperch

Green sunfish

Fish species common name

0 5 10 15 20 25 30 35 40

Number of fish per species

Average number of juveniles

or glochidia per fish

0

1.5

2.0

2.5

3.0

1.0

0.5

3.5

Total number of juveniles or glochidia

0

30

40

50

60

80

20

10

70

EXPLANATION

EXPLANATION

Catostomidae

Centrarchidae

Cyprinidae

Ictaluridae

Lepisosteidae

Percidae

 Family names for fish species collected 

Catostomidae

 Gray redhorse

Centrarchidae

 Redbreast sunfish

 Green sunfish

 Bluegill

 Longear sunfish

 Spotted bass

 Largemouth bass

Lepisosteidae

 Spotted gar

Percidae

 Slough darter

 Orangethroat darter

 Texas logperch

 Bigscale logperch

Cyprinidae

 Central stoneroller

 Red shiner

 Blacktail shiner

 Burrhead chub

 Bullhead minnow

Ictaluridae

 Channel catfish

 Flathead catfish

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Fish species common name, sorted by family—Color indicates family. Number indicates species

Proportion of glochidia extracted in

 the USGS laboratory from fish

 returned by the USFWS San 

 Marcos National Fish Hatchery 

 and Technology Center USGS, U.S. Geological Survey

USFWS, U.S. Fish and Wildlife Service

Proportion of glochidia or juveniles

 recovered at the USFWS San 

 Marcos National Fish Hatchery 

 and Technology Center

Zero valueZero valueZero valueZero valueZero value

1

2 3

4

5

6

7

8 9 10 11 12

13

15

16

18 19 17

14

A.

B.

Figure 16. Composite from all sites sampled in 2013 of A, average number of juvenile mussels or glochidia collected per fish species; 

and B, total number of glochidia collected per fish species from fish held at the U.S. Fish and Wildlife Service San Marcos National Fish 

Hatchery and Technology Center as part of a mussel host-fish study, central and southeastern Texas, 2012–13.
50 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

juvenile mussels on average (1.48), followed by ictalurids 

(1.3) and percids (0.29). Centrarchids also retained the most 

glochidia per individual on average from fish returned by the 

hatchery (0.23) followed by ictalurids (0.20). All centrarchid 

and percid species that were submitted to the hatchery released 

juvenile mussels (fig. 16A, table 6).

Summary

In 2012–13, the U.S. Geological Survey (USGS), in 

cooperation with the U.S. Fish and Wildlife Service (USFWS), 

completed the first phase of a two-phase study of mussel 

host-fish relations for five endemic mussel species in central 

and southeastern Texas that were State-listed as threatened on 

January 17, 2010: (1) Texas fatmucket (Lampsilis bracteata), 

(2) golden orb (Quadrula aurea), (3) smooth pimpleback 

(Quadrula houstonensis), (4) Texas pimpleback (Quadrula 

petrina), and (5) Texas fawnsfoot (Truncilla macrodon). On 

October 6, 2011, the USFWS announced the completion of 

a status review and determined that the five mussel species 

warranted listing under the Endangered Species Act; however, 

listing of these species at that time was precluded by higher 

priority listing actions, and currently (December 2014), they 

remained unlisted.

Freshwater mussels are long-lived, sedentary organisms 

that spend their larval stage as obligate parasites on the gills 

or fins of fishes, and many of these larvae, which are referred 

to as “glochidia,” can survive only on a narrow range of 

host-fish species. Results from both study phases are likely to 

provide information useful for propagation of rare mussels, 

reintroduction of host fish, population and reproduction 

monitoring, habitat restoration and enhancement, and adaptive 

management.

The abundance of host fish, frequency of parasitism in 

fish, and frequency of juvenile mussels or glochidia recovered 

from hatchery-held fish was assessed by collecting fish 

and mussels at 14 sites distributed among seven streams in 

central and southeastern Texas. All fish collected and assessed 

in this study were wild-caught. Qualitative surveys of the 

resident mussel communities were made, focusing on the 

five candidate species. A subsample (3 percent in 2012 and 

19 percent in 2013) of the fish collected during aquatic biota 

surveys were submitted to the USFWS San Marcos National 

Fish Hatchery and Technology Center to collect juvenile 

mussels or glochidia recovered from host fish, which were 

held in holding tanks. All fish not sent to the hatchery were 

assessed for glochidia in the field or in the USGS Texas Water 

Science Center laboratory in Austin, Tex. Juvenile mussels and 

glochidia that were recovered from fish at the hatchery were 

submitted for use in the second phase of this study for the 

development of deoxyribonucleic acid (DNA) identification 

keys to determine mussel and host-fish relationships through 

DNA-based molecular identification (DNA typing of the 

juvenile mussels and glochidia). Reporting on the results of 

DNA-based molecular identification research is beyond the 

scope of this report.

In 2012, the majority of the fish that were collected, 

in terms of total number and species types, belonged to the 

sunfish family Centrarchidae (centrarchids; 1,277 individuals 

and at least 10 species). Redbreast sunfish (Lepomis auritus) 

was the most common species collected in 2012 (603 

individuals), but largemouth bass (Micropterus salmoides) 

were caught at all 10 sites. The largest number of individuals 

(416) was collected at the Llano Castell site (Llano River at 

Castell, Tex.) on August 22, 2012, whereas the largest number 

of species (19) was collected at the San Saba Menard site (San 

Saba River near Menard, Tex.) on May 22, 2012. 

In 2013, the majority of the fish that were collected, in 

terms of total number and species types, were centrarchids 

(763 individuals) and cyprinids (10 species), respectively. 

Blacktail shiner (Cyprinella venusta) was the most common 

species collected in 2013 (287 individuals), but bluegill 

(Lepomis macrochirus) was the only species that was caught 

at all nine sites. The largest number of individuals (382) and 

species (19) was collected from the Colorado Columbus site 

(Colorado River near Columbus, Tex.) on June 11, 2013. 

A minimum of two fish (any species) parasitized with 

glochidia was collected from each of the 10 sites sampled 

during 2012. The highest percentage of parasitized fish 

(19.1 percent) was measured at the Guadalupe Victoria site 

(Guadalupe River near Victoria, Tex.). Parasitized individuals 

were collected from five families of fish in 2012. The catfish 

family Ictaluridae (ictalurids) exhibited the highest proportion 

of parasitized fish (12.1 percent), but the centrarchids had the 

highest number of parasitized individuals (87).

Nine sites were sampled in 2013, and the Pedernales 

Fredericksburg site (Pedernales River near Fredericksburg, 

Tex.) had the highest proportion of parasitized fish at 

22.7 percent. The percentage of parasitized fish increased 

substantially at the Pedernales Fredericksburg site between 

2012 (1.4 percent) and 2013 (22.7 percent), likely because 

the sampled area was relocated. Parasitized individuals were 

only collected from three families of fish in 2013. Ictalurids 

exhibited the highest frequency of parasitism (26.5 percent), 

but centrarchids had the highest number of parasitized 

individuals (40).

Of the fish that were not sent to the hatchery but assessed 

for glochidia in the field or in the laboratory in 2012, at least 

13 species were parasitized, and longear sunfish (Lepomis 

megalotis) was the species with the highest percentage of 

parasitized individuals (17.3 percent). Of the fish that were not 

sent to the hatchery but assessed for glochidia in the field or 

in the laboratory in 2013, only eight species were parasitized, 

and flathead catfish (Pylodictis olivaris) was the species 

with the highest percentage of parasitized individuals (42.9 

percent). The number of parasitized species based on field and 

laboratory observations was lower in 2013 than in 2012, but 

when data from the hatchery are included, the total number of 

parasitized species in 2013 surpasses the number of parasitized 

species collected in 2012.
References 51

With the exception of the San Antonio Charco site, fish 

were submitted to the hatchery from all sampling sites in 2013. 

During the first sampling period in 2013 (April 1–5), slightly 

more than half (16 out of 29) of the fish species (on a per site 

basis) that were submitted to the hatchery released juvenile 

mussels or glochidia (hereinafter juvenile mussels; juvenile 

mussels and glochidia were not differentiated in hatcheryheld fish), and individuals from 5 of the 16 fish species 

retained glochidia after completing trials at the hatchery. 

Largemouth bass collected from the Guadalupe Kerrville site 

and spotted bass (Micropterus punctulatus) collected from 

the Guadalupe Victoria site released more than four juvenile 

mussels per individual on average. Compared to the other 

sampling periods in 2013, substantially fewer glochidia per 

fish were present on fish submitted to the hatchery during 

the second sampling period in 2013 (April 29–May 2); only 

longear sunfish (collected at the Colorado San Saba site 

[Colorado River near San Saba, Tex.]) averaged more than 

one juvenile mussel per fish. None of the fish collected at the 

Pedernales Fredericksburg and Colorado Nada (Colorado 

River near Nada, Tex.) sites released juvenile mussels at the 

hatchery. Although only two sites were sampled during the 

third sampling period in 2013 (June 10–11), more juvenile 

mussels were recovered at the hatchery during this sampling 

period (107) than were recovered during the first two sampling 

periods in 2013 combined (102). An average of 17 juvenile 

mussels were recovered per largemouth bass submitted to the 

hatchery from the Guadalupe Victoria site during the third 

sampling period, and all four species of fish submitted from 

the Guadalupe Victoria site released juvenile mussels at the 

hatchery, which equals an average of 7.3 juvenile mussels 

per fish.

A total of 19 fish species collected at nine sites was 

submitted to the hatchery in 2013, and 14 of these species 

released juvenile mussels at the hatchery. The three most 

productive species, in terms of average juvenile mussels 

recovered, were longear sunfish, spotted bass, and largemouth 

bass, each of which averaged more than two juvenile mussels 

recovered per individual.

References

Bogan, A.E., 1993, Freshwater bivalve extinctions (Mollusca 

Unionidae)—A search for causes: American Zoologist, v. 

33, no. 6, p. 599–609.

Boyer, S.L., Howe, A.A., Juergens, N.W., and Hove, M.C., 

2011, A DNA-barcoding approach to identifying juvenile 

freshwater mussels (Bivalvia Unionidae) recovered from 

naturally infested fishes: Journal of the North American 

Benthological Society, v. 30, no. 1, p. 82–194.

Darr, Alexander, Korpinen, Samuli, Westerbom, Mats, and 

Nygård, Henrik, 2013, Population structure of long-lived 

macrozoobenthic species: HELCOM Core Indicator 

Report, 15 p., accessed November 12, 2014, at http://www.

helcom.fi/Core%20Indicators/HELCOM-CoreIndicator_

Population_structure_of_long-lived_macrozoobenthic_

species.pdf.

Great Plains Nature Center, 2014, Anatomy of unionid 

mussels: Accessed October 1, 2014, at http://www.gpnc.org/

shells.htm.

Gustafson, R.G., and Iwamoto, E.M., 2005, A DNAbased identification key to Pacific Northwest freshwater 

mussel glochidia—Importance to salmonid and mussel 

conservation: Northwest Science, v. 79, no. 4, p. 233–245.

Haag, W.R., 2012, North American freshwater mussels—

Natural history, ecology, and conservation: Cambridge, 

Cambridge University Press, 505 p.

Haag, W.R., and Warren, M.L., 1998, Role of ecological 

factors and reproductive strategies in structuring freshwater 

mussel communities: Canadian Journal of Fisheries and 

Aquatic Sciences, v. 55, no. 2, p. 297–306. 

Hambrook, J.A., and Eberle, Michael, 2000, What makes 

a healthy environment for native freshwater mussels: 

U.S. Geological Survey Fact Sheet 124-00, 6 p., accessed 

November 14, 2014, at http://pubs.usgs.gov/fs/2000/0124/

report.pdf.

Howells, R.G., 2010, Guide to Texas freshwater mussels

(3d ed.): Kerrville, Tex., BioStudies, 122 p., accessed 

September 29, 2014, at http://www.eahcp.org/files/adminrecords/NEPA-docs/Howells,%202010.pdf.

Howells, R.G., Neck, R.W., and Murray, H.D., 1996, 

Freshwater mussels of Texas: Austin, Texas, Texas Parks 

and Wildlife Department, 224 p.

Johnson, M.S., Caccavale, P.D., Randklev, C.R., and Gibson, 

J.R., 2012, New and confirmed fish hosts for the threatened 

freshwater mussel Lampsilis bracteata (Gould, 1855), the 

Texas Fatmucket (Bivalvia—Unionidae): The Nautilus, v. 

126, no. 4, p. 148–149.

Kneeland, S.C., and Rhymer, J.M., 2008, Determination of 

fish host use by wild populations of rare freshwater mussels 

using a molecular identification key to identify glochidia: 

Journal of the North American Benthological Society, v. 27, 

no. 1, p. 150–160.

Lellis, W.A., White, B.S.J., Cole, J.C., Johnson, C.S., 

Devers, J.L., Gray, E.V.S., and Galbraith, H.S., 2013, 

Newly documented host fishes for the eastern elliptio 

mussel Elliptio complanata: Journal of Fish and Wildlife 

Management, v. 4, no. 1, p. 75–85.
52 Abundance of Host Fish and Frequency of Glochidial Parasitism from Hatchery-Held Fish, Central and Southeastern Texas, 2012–13

Lydeard, Charles, Cowie, R.H., Ponder, W.F., Bogan, A.E., 

Bouchet, Philippe, Clark, S.A., Cummings, K.S., Frest, 

T.J., Gargominy, Olivier, Herbert, D.G., Herschler, Robert, 

Perez, K.E., Roth, Barry, Seddon, Mary, Strong, E.E., and 

Thompson, F.G., 2004, The global decline of nonmarine 

mollusks: Bioscience, v. 54, no. 4, p. 321–330.

Martel, A.L., and Lauzon-Guay, J.S., 2005, Distribution and 

density of glochidia of the freshwater mussel Anodonta 

kennerlyi on fish hosts in lakes of the temperate rain forest 

of Vancouver Island: Canadian Journal of Zoology, v. 83, 

no. 3, p. 419–431.

Medical Museion, 2010, The history of the microplate—A 

ubiquitous biomedical lab technology: Accessed on 

September 23, 2014, at http://www.museion.ku.dk/2010/11/

the-history-of-microplate-technology/.

Minnesota Department of Natural Resources, 2014, 

Importance of mussels: Accessed on September 9, 2014, at 

http://www.dnr.state.mn.us/mussels/importance.html.

Neck, R.W., 1982, A review of interactions between humans 

and freshwater mussels in Texas, in Davis, J.R., ed., 

Proceedings of the symposium on recent benthological 

investigations in Texas and adjacent states: Aquatic Science 

Section, Texas Academy of Science, p. 169–182.

Pardo, Isabel, and Armitage, P.D., 1997, Species 

assemblages as descriptors of mesohabitats: 

Hydrobiologia, v. 344, no. 1–3, p. 111–128, accessed 

May 6, 2013, at http://link.springer.com/content/

pdf/10.1023%2FA%3A1002958412237.pdf.

Randklev, C.R., Kennedy, J.H., and Lundeen, B.J., 2009, 

Distributional survey and habitat utilization of freshwater 

mussels (family Unionidae) in the Lower Brazos and 

Sabine River Basins: Interagency Report to the Texas Water 

Development Board, 57 p.

Strayer, D.L., 1999, Use of flow refuges by unionid mussels 

in rivers: Journal of the North American Benthological 

Society, v. 18, no. 4, p. 468–476.

Strayer, D.L., and Smith, D.R., 2003, A guide to sampling 

freshwater mussel populations: American Fisheries Society 

Monograph 8, American Fisheries Society, Bethesda, Md., 

110 p.

Szafoni, R.E., 2001, Protocol for integrating freshwater mussel 

surveys into IDNR/IEPA stream basin surveys (version 2.0): 

Charleston, Ill., Illinois Department of Natural Resources, 

Office of Resource Conservation and Natural Heritage, 5 p.

Texas Parks and Wildlife Department, 2010, TPWD lists 

15 freshwater mussels as state threatened: Accessed 

on September 23, 2014, at http://www.tpwd.texas.gov/

huntwild/wild/wildlife_diversity/nongame/mussels/media/

state_mussels.pdf.

Texas Parks and Wildlife Department, 2014, Texas mussel 

watch survey data sheet: Accessed on September 25, 2014, 

at http://www.tpwd.state.tx.us/huntwild/wild/wildlife_

diversity/texas_nature_trackers/media/tx_mussel_watch_

data_sheet.pdf.

University of Texas, 2012, Ichthyology: Texas Natural Science 

Center: Accessed February 27, 2014, at http://www.utexas.

edu/tmm/tnhc/fish/.

U.S. Fish and Wildlife Service, 2011a, Distribution maps 

of each of the five central Texas mussels: Accessed on 

September 29, 2014, at http://www.fws.gov/southwest/es/

Documents/R2ES/5_central_Texas_mussels_Maps_2011.

pdf.

U.S. Fish and Wildlife Service, 2011b, Frequently asked 

questions on the 12-month finding for five central Texas 

mussels: Accessed December 2014, at http://www.fws.gov/

southwest/es/Documents/R2ES/5_central_Texas_mussels_

FAQs_2011.pdf.

U.S. Fish and Wildlife Service, 2011c, Service determines five 

central Texas mussel species warrant protection under the 

Endangered Species Act: Accessed on September 23, 2014, 

at http://www.fws.gov/southwest/es/Documents/R2ES/5_

central_Texas_mussels_NewsRelease_2011.pdf.

U.S. Fish and Wildlife Service, 2013, Endangered and 

threatened wildlife and plants—Review of native species 

that are candidates for listing as endangered or threatened: 

Federal Register, v. 78, no. 226, p. 70128–70130 and p. 

70156–70157, accessed October 1, 2014, at http://www.gpo.

gov/fdsys/pkg/FR-2013-11-22/pdf/2013-27391.pdf.

U.S. Geological Survey, 2014, National Water Information 

System: Accessed September 22, 2014, at http://waterdata.

usgs.gov/tx/nwis/.

Vaughn, C.C., and Taylor, C.M., 1999, Impoundments and 

the decline of freshwater mussels—A case study of an 

extinction gradient: Conservation Biology, v. 13, no. 4, p. 

912–920.

Watters, T.G., 1999, Freshwater mussels and water quality—A 

review of the effects of hydrologic and instream habitat 

alterations, in Tankersely, R.A., Warmolts, D.J., Watters, 

G.T., Armitage, B.J., Johnson, P.D., and Butler, R.S., eds., 

Proceedings of the First Freshwater Mollusk Conservation 

Society Symposium: Columbus, Ohio, Ohio Biological 

Survey, p. 261–272.

WildEarth Guardians, 2014, Species conservation: Accessed 

September 18, 2014, at http://www.wildearthguardians.org/

site/PageServer?pagename=species.
References 53

Williams, J.D., Warren, M.L., Cummings, K.S., Harris, J.L., 

and Neves, R.J., 1993, Conservation status of freshwater 

mussels of the United States and Canada: Fisheries, v. 18, 

no. 9, p. 6–22.

Ziuganov, Valery, Kaliuzhin, Sviatoslav, Beletsky, Victor, 

and Popkovitch, Ekaterina, 2001, The pearl mussel-salmon 

community in the Varzuga River, northwest Russia—

Problems of environmental impacts, in Bauer, G., and 

Watchler, K., eds., Ecology and evolution of freshwater 

mussels Unionidea: Springer, Berlin, Ecological Studies, v. 

145, p. 359–366.

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