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Before this study, researchers had not systematically surveyed the Río Conchos, a tributary of the Rio Grande located in northern Mexico, for freshwater mussels. The Texas hornshell, Popenaias popeii, an endangered species under the United States Endangered Species Act, occurs in the main stem of the Rio Grande near its confluence with the Río Conchos. The Texas hornshell's proximity to the Río Conchos prompted us to survey to determine whether P. popeii also occurs within the Conchos basin. Additionally, previous researchers described the Conchos disk, Disconaias conchos, from the Río Conchos but, to date, no one has reported live individuals of this species. The goal of this study was to determine the status of mussels within the Río Conchos basin and to provide a baseline for future monitoring efforts. We qualitatively surveyed 11 sites within the Río Conchos basin in May 2018. In total, we found two live individuals of the paper pondshell, Utterbackia imbecillis, at one site in the Río San Pedro, a tributary of the Conchos River, and as shells of recently live individuals at two sites in the Río Conchos. We found D. conchos as relict shells only at three sites, two in the Río Conchos and one in a tributary of the river at Coyame. The lack of live or fresh-dead material suggests that D. conchos is extinct. We also found live individuals of nonnative Asian clams (Corbicula spp.) at 10 sites. Sand and gravel mining, high organic pollution, and inadequate instream flows were evident throughout the basin and might explain the general absence of mussels. RESUMEN-El río Conchos, un afluente del río Bravo ubicado en el norte de México, nunca había sido examinado sistemáticamente en búsqueda de mejillones de agua dulce. El mejillón, Popenaias popeii, una especie en peligro de extinción bajo el Acta de Especies Amenazadas de los Estados Unidos, habita en la parte principal del río Bravo cerca de su confluencia con el río Conchos. Así mismo, por su cercanía al río Conchos, se inició la búsqueda para determinar si P. popeii también ocurre dentro de la cuenca del Conchos. Además, a la fecha no se ha reportado la existencia de individuos vivos de Conchos Disk, Disconaias conchos, cuyo origen sea el río Conchos. El objetivo de este estudio fue determinar el estado de los mejillones dentro de la cuenca del río Conchos y proporcionar la línea base para futuros esfuerzos de monitoreo. En mayo del 2018, realizamos una inspección cualitativa en 11 sitios de la cuenca del río Conchos. En total, encontramos dos individuos vivos de la Paper Pondshell, Utterbackia imbecillis, en un sitio del río San Pedro, afluente del Conchos, así como conchas recién muertas en dos sitios del río Conchos. Se encontraron conchas antiguas de D. conchos solo en tres sitios: dos en el río Conchos y una en un afluente del río en Coyame. La falta de D. conchos vivas o rastros frescos podría implicar que está extinta. También encontramos individuos vivos de la almeja asiática no nativa (Corbicula spp.) en 10 sitios. El minado de arena y grava, la alta contaminación orgánica y flujos alimentarios inadecuados de agua fueron evidentes en toda la cuenca y quizá expliquen la ausencia de mejillones.
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THE SOUTHWESTERN NATURALIST 64(3/4): 180–186 SEPTEMBER/DECEMBER 2019
STATUS OF FRESHWATER MUSSELS (UNIONIDAE) OF THE R´
IO
CONCHOS BASIN, CHIHUAHUA, MEXICO
JEREMY S. TIEMANN,* KENTARO INOUE,J.ALFREDO RODR´
IGUEZ-PINEDA,MICHAEL HART,KEVIN S. CUMMINGS,
EDNA NARANJO-GARC´
IA,AND CHARLES R. RANDKLEV
Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820 (JST, KSC)
Texas A&M University, Natural Resources Institute, Texas A&M AgriLife Research Center, Dallas, TX 77843 (KI, MH, CRR)
World Wildlife Fund–M´
exico, Chihuahua, M´
exico 31100 (JARP)
Instituto de Biolog´
ıa, Departamento de Zoolog´
ıa, Universidad Nacional Aut´
onoma de M´
exico, M´
exico City, M´
exico 04510 (ENG)
*Correspondent: jtiemann@illinois.edu
ABSTRACT—Before this study, researchers had not systematically surveyed the R´ıo Conchos, a tributary of the
Rio Grande located in northern Mexico, for freshwater mussels. The Texas hornshell, Popenaias popeii,an
endangered species under the United States Endangered Species Act, occurs in the main stem of the Rio
Grande near its confluence with the R´ıo Conchos. The Texas hornshell’s proximity to the R´ıo Conchos
prompted us to survey to determine whether P. popeii also occurs within the Conchos basin. Additionally,
previous researchers described the Conchos disk, Disconaias conchos, from the R´ıo Conchos but, to date, no one
has reported live individuals of this species. The goal of this study was to determine the status of mussels within
the R´ıo Conchos basin and to provide a baseline for future monitoring efforts. We qualitatively surveyed 11
sites within the R´ıo Conchos basin in May 2018. In total, we found two live individuals of the paper pondshell,
Utterbackia imbecillis, at one site in the R´ıo San Pedro, a tributary of the Conchos River, and as shells of recently
live individuals at two sites in the R´ıo Conchos. We found D. conchos as relict shells only at three sites, two in the
ıo Conchos and one in a tributary of the river at Coyame. The lack of live or fresh-dead material suggests that
D. conchos is extinct. We also found live individuals of nonnative Asian clams (Corbicula spp.) at 10 sites. Sand
and gravel mining, high organic pollution, and inadequate instream flows were evident throughout the basin
and might explain the general absence of mussels.
RESUMEN—El r´ıo Conchos, un afluente del r´ıo Bravo ubicado en el norte de M´exico, nunca hab´ıa sido
examinado sistem´aticamente en b´
usqueda de mejillones de agua dulce. El mejill´on, Popenaias popeii, una
especie en peligro de extinci´on bajo el Acta de Especies Amenazadas de los Estados Unidos, habita en la parte
principal del r´ıo Bravo cerca de su confluencia con el r´ıo Conchos. As´ı mismo, por su cercan´ıa al r´ıo Conchos,
se inici´olab
´
usqueda para determinar si P. popeii tambi´en ocurre dentro de la cuenca del Conchos. Adem´as, a
la fecha no se ha reportado la existencia de individuos vivos de Conchos Disk, Disconaias conchos, cuyo origen
sea el r´ıo Conchos. El objetivo de este estudio fue determinar el estado de los mejillones dentro de la cuenca
del r´ıo Conchos y proporcionar la l´ınea base para futuros esfuerzos de monitoreo. En mayo del 2018,
realizamos una inspecci´on cualitativa en 11 sitios de la cuenca del r´ıo Conchos. En total, encontramos dos
individuos vivos de la Paper Pondshell, Utterbackia imbecillis, en un sitio del r´ıo San Pedro, afluente del
Conchos, as´ı como conchas reci´en muertas en dos sitios del r´ıo Conchos. Se encontraron conchas antiguas de
D. conchos solo en tres sitios: dos en el r´ıo Conchos y una en un afluente del r´ıo en Coyame. La falta de D.
conchos vivas o rastros frescos podr´ıa implicar que est´a extinta. Tambi´en encontramos individuos vivos de la
almeja asi´atica no nativa (Corbicula spp.) en 10 sitios. El minado de arena y grava, la alta contaminaci ´on
org´anica y flujos alimentarios inadecuados de agua fueron evidentes en toda la cuenca y quiz´a expliquen la
ausencia de mejillones.
Freshwater mussels (Order Unionida), hereafter mus-
sels, are among the most imperiled groups of aquatic
organisms because of widespread anthropogenic distur-
bances (Williams et al., 1993; Strayer et al., 2004). Many
North American streams, from small creeks to large rivers,
harbor declining populations. Mussel assemblage struc-
ture is often radically different than historical baselines,
such that rare and sensitive species are typically extirpated
(Williams et al., 1993; Strayer et al., 2004). Mussels play
important roles in aquatic ecosystems by facilitating
nutrient cycling, stabilizing substrates, and increasing
habitat heterogeneity (Vaughn and Hakenkamp, 2001;
Vaughn et al., 2008; Allen and Vaughn, 2011). Population
declines and changes to assemblage structure can result
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in diminished services provided by mussels, which, in
turn, can have long-term negative consequences for the
ecological function of riverine systems (Vaughn et al.,
2015; Vaughn and Hoellein, 2018).
Assessing the distribution and status of mussels is an
important component of conservation and management
programs (National Native Mussel Conservation Commit-
tee, 1998; Haag and Williams, 2014; Freshwater Mollusk
Conservation Society, 2016). However, in places such as
the southwestern United States and northern Mexico,
basic knowledge regarding species ranges, location of
significant populations, and the status of those popula-
tions is lacking or just beginning to emerge. This lack of
knowledge is particularly true for the Rio Grande
drainage, which historically harbored at least 15 species
(Howells, 2001), of which the Texas hornshell, Popenaias
popeii, Salina mucket, Potamilus metnecktayi, and Mexican
fawnsfoot, Truncilla cognata, are considered Texas state-
threatened or endangered and have been federally-listed
(P. popeii, endangered) or are under review (P. metnecktayi
and T. cognata) for protection under the United States
Endangered Species Act (United States Fish and Wildlife
Service, 2009, 2016, 2018; Texas Parks and Wildlife
Department, 2010, 2020). Only recently have surveys
within the main stem of the Rio Grande and its major
tributaries in the United States provided insight to the
conservation status of the mussel fauna (Randklev et al.,
2018). However, researchers have yet to formally survey
major tributaries of the Rio Grande in Mexico, such as the
ıo Conchos, for mussels. Such information is important
because populations of threatened species might exist
within these systems, thus improving the known distribu-
tion of focal species. Alternatively, they also might be
absent, confirming current hypotheses on the range and
status for these same taxa. Wildlife biologists know P.
popeii from the main stem Rio Grande near its confluence
with the R´ıo Conchos (Randklev et al., 2018) and the
species could occur in the R´ıo Conchos basin (Johnson,
1999), whereas no reports exist for the other two species
from the under-sampled R´ıo Conchos.
The mussel fauna of the R´ıo Conchos is poorly known
due to its remote location and limited points of access. As
a result, hearsay and anecdotal observations based largely
upon incidental encounters are the basis for some species
accounts (Howells, 2001). For example, Metcalf and Stern
(1976) reported two species from the basin but did not
offer a species list. Neck (1984) recounted a story of how
D. W. Taylor had told A. L. Metcalf that he had found
living specimens of the Rio Grande monkeyface, Quadrula
couchiana, in the R´ıo Conchos near Chihuahua, yet Taylor
published no data and deposited no specimens that we
are aware of in a natural history museum collection.
Taylor (1997) described the Conchos disk, Disconaias
conchos, from the R´ıo Conchos from specimens collected
near Julimes, Rosetilla, and Saucillo, Chihuhua, in 1969;
however, to date, no one has reported live individuals of
this species, nor has anyone reported the species from
outside the R´ıo Conchos basin, where it is thought to be
endemic. Johnson (1999), when describing the distribu-
tion of mussels in the R´ıo Conchos, stated that ‘‘only
Disconaias conchos Taylor has been reported’’ from the
river, yet he listed D. conchos,P. popeii,Q. couchiana, and
paper pondshell, Utterbackia imbecillis, in tabular form in
the article. Finally, Howells and Garrett (1995) sampled
four sites in the R´ıo Conchos in 1994 during their desert
fish surveys, but only found unidentified subfossil valves
downstream of Julimes; Howells (2001) later reported
these individuals as D. conchos.
According to Graf and Cummings (2018), only 12 lots
of R´ıo Conchos mussels exist in the 15 museums they
examined, and based on these limited collections,
biologists know only three species of mussels from the
basin: Tampico pearlymussel, Cyrtonaias tampicoensis;D.
conchos; and U. imbecillis. We conducted a formal survey of
the R´ıo Conchos because of the lack of contemporary
baseline information and uncertainty regarding the
historical fauna. Data derived from this effort are critical
in resolving the conservation status of rare taxa like P.
popeii occurring in the Rio Grande drainage and
expanding our knowledge of mussel assemblages in the
ıo Conchos basin.
MATERIALS AND METHODS—We conducted our study in the R´ıo
Conchos basin in the Mexican state of Chihuahua. The R´ıo
Conchos originates in the Sierra Madre Occidental of western
Chihuahua and then flows eastward through the Chihuahuan
Desert (Guti´errez and Borrego, 1999; Johnson, 1999). The R´ıo
Conchos is nearly 750 km in length and drains an area of about
67,000 km
2
(Barrios et al., 2009; Montero-Mart´ınez and Ib´a˜
nez-
Hern´andez, 2017). By volume, it is the largest tributary of the
Rio Grande. The R´ıo Conchos joins the Rio Grande at the town
of Ojinaga, Mexico, opposite Presidio, Texas, and the basin
comprises 14% of the binational (Mexico–United States) R´ıo
Bravo–Rio Grande drainage (Barrios et al., 2009). In fact, the
ıo Conchos supplies >75% of the flow through the Big Bend
region of Texas (Guti´errez and Borrego, 1999). The climate is
temperate and subhumid at the upper portion and dry at the
lower portion of the basin (De la Maza Benignos, 2009), with
about two-thirds of the basin occurring in the Chihuahuan
Desert. Annual precipitation in the basin ranges from 700 mm
in the upper portion to 250 mm in the lower portion (Barrios et
al., 2009), of which 90% occurs during the rainy season from
July to September. Dams impound the R´
ıo Conchos basin in 10
places, including three large reservoirs, La Boquilla Dam
(Toronto Reservoir), Francisco I. Madero Dam (Francisco I.
Madero Reservoir), and Luis L. Leon Dam (El Granero
Reservoir), that were built to provide hydroelectricity, irrigation,
and flood control (Guti´errez and Borrego, 1999). Approximate-
ly 90% of the annual water volume is diverted for agricultural
purposes. Generally degraded water quality throughout much of
the basin is due to industrial effluent, pesticides, sand and gravel
mining, raw sewage, irrigation returns, and inadequate flows
(Rubio et al., 2004, 2013; Mahlknecht et al., 2008). The R´ıo
Conchos basin also is prone to long periods of drought (Mu ˜
noz-
Robles et al., 2006; Reyes-G´omez et al., 2006) and scientists
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expect climate change to amplify the effects of these droughts.
Raynal-Villase˜
nor and Rodr´ıguez-Pineda (2008) projected that
within 30 years, precipitation will decrease by 2.4–11.3%,
evaporation will increase 2.0–7.3%, and air temperatures will
rise 1–38C. The combined effects of less rain and warmer
temperatures will likely result in reduced water availability for
aquatic organisms such as mussels.
We conducted a survey for mussels at 11 sites in the R´ıo
Conchos basin, Chihuahua, Mexico, from 6 May to 9 May 2018
(Fig. 1). We selected sites based upon the limited historical data
from natural history museums or selected areas that were easily
accessible and had suitable habitat (e.g., free-flowing and
heterogeneous substrates) and had willing landowners. Depths
at most sites were <1.5 m, which allowed for snorkeling. We used
qualitative tactile searches between 1 and 5 person-hours at each
site (sites were ca. 100–500 m in length). We also walked the
shoreline to look for the presence of shells. We retained spent
shells as voucher specimens and deposited them in the Illinois
Natural History Survey Mollusk Collection, Champaign, Illinois.
Nomenclature discussed in this report follows Graf and
Cummings (2007) and the updates provided by Williams et al.
(2017). Because of logistical constraints (e.g., time), we noted
minimal habitat data at each site. We made no efforts to quantify
habitat or site characteristics (e.g., width), and therefore do not
report these characteristics.
RESULTS—We found evidence of U. imbecillis at three
sites in the basin, including two live individuals at site 6,
fresh-dead shells (e.g., pristine shell but no tissue
present) at site 9, and shell fragments at site 5 (Table 1;
Fig. 1). We found D. conchos (Fig. 2) only as relict shells
(e.g., periostracum eroded, nacre faded, shell chalky) and
only at sites 2, 3, and 11 (Table 1; Fig. 1). We failed to
collect C. tampicoensis, P. popeii,P. metnecktayi,T. cognata,or
Q. couchiana during our surveys of the R´ıo Conchos basin.
We also found live individuals of nonnative Asian clams
(Family Cyrenidae) at all but one site (Table 1), and
collected thousands of individuals at some sites. Based
upon shell morphology, we identified at least two
Corbicula species in the R´ıo Conchos basin, which we
tentatively identified as Corbicula fluminea and Corbicula
largillierti. These taxa also have been referred to as forms
A and B, respectively, in the literature (Lee et al., 2005;
Tiemann et al., 2017).
DISCUSSION—Based on the results of our survey, we were
unable to find any evidence that the U.S. federally
endangered P. popeii occurred in the R´ıo Conchos basin
despite its occurrence in the main stem Rio Grande near
its confluence with the R´ıo Conchos (Randklev et al.,
2018). The lack of historical evidence for this species in
this basin combined with our survey results suggests P.
popeii may have never occurred in the R´ıo Conchos basin.
However, more survey work is needed, particularly in the
lower portion of the basin, to determine if a small,
isolated population occurs in the canyons near the
confluence with Rio Grande.
We are able to confirm the presence of relict shell for
D. conchos and live or fresh-dead individuals for U.
imbecillis in the R´ıo Conchos basin. To date, there is little
to no evidence that D. conchos is currently extant in the
basin. Howells (2001) reported collecting one fresh-dead
juvenile near Julimes (between our sites 9 and 11) in
1994,butweknowofnovoucherspecimensor
photographs and have observed no recent material. We
found no evidence of C. tampicoensis. The only indication
this species occurred in the R´ıo Conchos basin is one
museum lot at the Smithsonian National Museum of
Natural History (USNM 1152200, n=37 valves) from the
‘‘ıo Conchos at Saucillo, past Rosetilla dam completion,’’
collected by Jerry Landye, 30 August 1971. We question
the validity of the identification because the shell shape is
not indicative of C. tampicoensis. While we have not seen
the lot in hand, we are of the opinion the specimens are
D. conchos based upon photographs. A. L. Herrera labeled
a second lot (USNM 347186) as coming from ‘‘ Conchas
R., Tamaulipas, Mexico.’’ The R´ıo Conchos is located in
the Mexican state of Chihuahua, not Tamaulipas. It is
probable that Herrera collected these specimens in the
ıo San Fernando, which is alternatively called the R´ıo
Conchos, and is the site where Herrera collected in
Mexico (Johnson, 1999; Graf and Cummings, 2018). As
for Q. couchiana, its status within this basin remains a
mystery, because, despite reports by Neck (1984) and
Johnson (1999), no published records or museum
specimens corroborate anecdotal accounts from this
basin and there is a distinct possibility researchers have
incorrectly attributed it to this basin. Williams et al.
(2017) speculated that Q. couchiana is extinct, which
might explain why we failed to find it. Finally, we failed to
find evidence of either P. metnecktayi or T. cognata. Based
on museum collections and our preliminary survey
results, neither species likely occurs in R´ıo Conchos, at
least not in modern times.
Our inability to locate live or fresh-dead C. tampicoensis
and D. conchos, despite finding live Corbicula and U.
imbecillis, indicates one of two possibilities: (1) they have
been reduced to small, isolated populations that are
difficult to detect using standard sampling methods or
(2) they no longer occur in the basin. Given the ongoing
water quality and quantity issues in the basin, coupled
with changes in temperature and precipitation, it is
possible neither species occurs in the basin (Metcalf,
1982; Guti´errez and Borrego, 1999; Raynal-Villase ˜
nor and
Rodr´ıguez-Pineda, 2008). For D. conchos, this hypothesis
would mean it is extinct because it is presumably a R´ıo
Conchos endemic. If researchers ever find live individuals
of D. conchos, it is imperative those specimens are properly
curated to facilitate analysis of soft-part morphology and a
genetic comparison between other taxa and those
currently placed in Disconaias.
There is a possibility that the D. conchos shell we
encountered and those found by earlier investigators are
not reflective of contemporary or historical individuals
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but instead of those from the Pleistocene or mid- to late
Holocene. Metcalf (1982) examined the mussel faunal
assemblages of the Pecos River over the last 13,000 years
and reported unidentified fossil specimens that resemble
D. conchos, although it is difficult to say whether they are
an exact match of what we found based on the photos he
presented. Metcalf (1982) noted that the Pecos River has
undergone ‘‘musselfaunaldepauperization’’ due to
changes in climate within this region since the Pleisto-
cene. It is plausible that the R´ıo Conchos has also
undergone such changes, resulting in the extirpation or
extinction of certain mussel taxa, and that researchers
have erroneously attributed the shells of those taxa to the
historical or contemporary fauna within this basin.
Assuming this scenario would mean the shell reported
by Howells (2001:Fig. 8) was a well-preserved specimen.
The amount of weathering a shell experiences is highly
variable, and without a reliable voucher specimen, we
cannot be certain (Strayer and Malcom, 2007; Atkinson et
al., 2018; Ilarri et al., 2018).
The finding of only one unionid species (U. imbecillis)
alive in our survey highlights the degree and breadth of
impairment of the R´ıo Conchos basin. Utterbackia imbecillis
is one of the most resilient mussel species in North
America, often found in soft substrates (e.g., mud and
silt) within littoral and backwater habitats of riverine
systems but also in artificial waterbodies such as reser-
voirs, canals, and ditches. This species also might be able
to reproduce without assistance of a host fish under
certain conditions, which is atypical for most unionid
mussel species and a beneficial adaptation for disturbed
environments (Howells et al., 1996; Watters et al., 2009;
Haag, 2012). Researchers have reported U. imbecillis
throughout the Rio Grande drainage (Howells et al.,
1996; Howells, 2001). However, considering that the live
individuals we collected were from an impoundment, we
cannot rule out that fish stocking introduced these U.
imbecillis, similar to what Metcalf and Smart (1972)
reported elsewhere in the Rio Grande drainage for the
giant floater, Pyganodon grandis.
Somewhat surprising, given the lack of live native
mussels, was the high prevalence and abundance of Asian
FIG. 1—Map depicting survey locations in the R´ıo Conchos basin, Chihuahua, Mexico. Site number indicates surveyed sites (see
Table 1). Star indicates the presence of live Utterbackia imbecillis (n=2), closed circles are where we found only dead and relict shells of
native mussels, and open circles are those sites where we failed to find evidence of native mussels.
September/December 2019 Tiemann et al.—Freshwater mussels of the R´ıo Conchos Basin 183
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clams in the basin. Members of the genus Corbicula are
some of the most successful of all aquatic invasive species
because they thrive in a variety of habitats and have
become established across the planet (Pigneur et al.,
2014a, 2014b). Corbicula have rapid growth, early maturity,
and elevated fecundity, making them better adapted to
persist in disturbed habitats (McMahon, 2002). We
encountered Corbicula at 10 of the 11 sites we surveyed
in the R´ıo Conchos basin, including artificial canals
(Table 1). One site (site 7) had an estimated density of
>200 individuals/m
2
based upon the number of individ-
uals collected in an approximated area sampled, whereas
spent Corbicula shell carpeted the streambed at several
other locations. The only site where we did not find
Corbicula was Julimes Hot Springs, where water tempera-
tures reach 428C (Carson et al., 2014), which exceeds the
upper thermal limits for mussels and Corbicula (Pandolfo
et al., 2010).
Our survey results combined with published instream
physicochemical conditions (e.g., Rubio et al., 2004, 2013;
Mahlknecht et al., 2008) indicate that the R´ıo Conchos is
currently unsuitable for mussels in most, if not all, areas.
The causes or mechanism for the imperilment of the
mussel fauna in the R´ıo Conchos is unknown but likely
related to alterations in the physical habitat and water
quantity and quality. During our survey we observed
organic pollution from agricultural activities, insufficient
flows, salinization (e.g., salt pans on the banks), and
active gravel mining. All of these activities can have
negative effects on riverine mussel populations because
they can affect survivorship, growth, and reproduction,
which are important biological endpoints that regulate
long-term population viability (Lydeard et al., 2004;
Strayer et al., 2004; Haag, 2012; Hart et al., 2019). Thus,
until watershed managers, like the federal water agency
Comisi´on Nacional del Agua (National Water Commis-
sion), address these issues, it is unlikely that conserva-
TABLE 1—Sites surveyed for freshwater bivalves in the R´ıo Conchos basin, Chihuahua, Mexico, in 2018 and species found at each
site. Site numbers correspond to Fig. 1.
Site Locality Species
1R´ıo Conchos, Puguis Canyon, 21 km SW Ojinaga (2983003.1300 N,
104844050.86 00 W)
Corbicula largillierti
2R´ıo Conchos, Cuchillo Pardo, 35 km WSW Ojinaga (29826042.4700 N,
104852050.84 00 W)
Disconaias conchos: relict shells
Corbicula largillierti
3 Trib. of the R´ıo Conchos, Coyame, MX Fed. Hwy 16 (29827059.9800 N,
1058405100 W)
Disconaias conchos; relict shells
Corbicula fluminea
Corbicula largillierti
4R´ıo Santa Isabel, 22 km SE Santa Isabel, MX Fed. Hwy 24 (28811012.48 00 N,
106813050.16 00 W)
Corbicula largillierti
5R´ıo Conchos, Zaragoza, MX Federal Hwy 24 (27827032.76 00 N, 105849018.8800 W) Utterbackia imbecillis; fragments
Corbicula largillierti
6R´ıo San Pedro, 22 km SW Rosales, upstream end of Pressa Francisco Madero
Reservoir (288404.0100 N, 105844016.4400 W)
Utterbackia imbecillis; live (n=2)
and fresh-dead shells
Corbicula largillierti
7 Small stream, 7 km WSW Rosales, below spillway Presa Francisco Madero
Reservoir (2889050.7600 N, 105837034.3200 W)
Corbicula largillierti
8 Canal, adjacent to R´ıo Conchos, 15 km SSE Julimes (28818019.44 00 N,
105820058.21 00 W)
Corbicula largillierti
9R´ıo Conchos, 17 km SSE Julimes (28817034.15 00 N, 105820012.1200 W) Utterbackia imbecillis; fresh-dead shells
Corbicula largillierti
10 Julimes Hot Springs, 2 km SSE Julimes (28824035.86 00 N, 105825025.1400 W) None
11 ıo Conchos, 6 km NNW Julimes (28828036.48 00 N, 105826021.12 00 W) Disconaias conchos; relict shells
Corbicula fluminea
Corbicula largillierti
FIG. 2—Relict shell of Disconaias conchos (length =118 mm)
collected from site 11 (see Fig. 1) on the R´ıo Conchos, 6 km
NNW Julimes, Chihuahua, Mexico, 9 May 2018 (Illinois Natural
History Survey collection number 88794).
184 vol. 64, no. 3/4The Southwestern Naturalist
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tionists and resource managers will have any success in
protecting and preserving what little remains of the
mussel fauna within the R´ıo Concho basin.
We thank A. Pieri (Texas A&M) for her assistance in the field;
C. Harper, G. Pandolfi, and S. Oetker (United States Fish and
Wildlife Service) for funding and logistical support; and A.
Lopez (Texas A&M Natural Resources Institute) for translating
the abstract. Funding was provided by a United States Fish and
Wildlife Service grant (F17AC01008).
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... Since then, it has spread throughout Mexico (Counts, 1991;López et al., 2019;Naranjo-García & Castillo-Rodríguez, 2017). It can become the most prevalent mollusk in streams (Czaja et al., 2022;Tiemann et al., 2020), and threatens to alter biologically diverse aquatic ecosystems in Mexico (Czaja et al., 2023). ...
... Once established, Corbicula often becomes the most abundant benthic bivalve in streams. Tiemann et al. (2020) reported densities > 200 individuals/m 2 in a small stream in the Río Conchos basin in northern Mexico. Corbicula life history characteristics (e.g., early sexual maturity, high fecundity, and ability to be actively and passively dispersed) favor rapid colonization and persistence in disturbed and unstable habitats (McMahon, 2002;Minchin & Boelens, 2018;Smith et al., 1986;Thompson & Sparks, 1977;Voelz et al., 1998). ...
... Data for Corbicula in Mexico and the shared drainages in the USA (i.e., Río Grande and Río Colorado) were compiled from 4 sources. First, we conducted qualitative freshwater mollusk surveys in the Grande, Pánuco, Papaloapan, and Usumacinta basins in the Mexican states of Chihuahua, San Luis Potosí, Veracruz, Tabasco, and Chiapas in 2017-2022 (see Inoue et al., 2020;Kiser et al., 2022;Tiemann et al., 2020). Second, we reviewed literature accounts of Corbicula in Mexico and shared drainages (Barba-Macías & Trinidad-Ocaña, 2017; Benson & Williams, 2021;Contreras-Arquieta & Contreras-Balderas, 1999;Counts, 1991;Counts et al., 2003;Czaja et al., 2022Czaja et al., , 2023Davis, 1980;Dinger et al., 2005;Fox 1970Fox , 1971Gutiérrez-Galindo et al., 1988;Hillis & Mayden, 1985;López-López et al., 2009, 2019Naranjo-García & Castillo-Rodríguez, 2017;Naranjo-García & Meza-Meneses, 2000;Naranjo-García & Olivera-Carrasco, 2014;Ramírez et al., 2022;Ramírez-Herrera & Urbano, 2014;Rico-Sánchez et al., 2020;Ruelas-Inzunza et al., 2007Tiemann et al., 2020;Torres-Orozco & Revueltas-Valle, 1996;Trinidad-Ocaña et al., 2018). ...
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Corbicula spp. are one of the most prolific aquatic invasive species in the world and can have negative effects on aquatic ecosystems. We performed qualitative field surveys, examined literature accounts and natural history museum holdings, and accessed citizen science data sources to document the distribution of Corbicula in Mexico and shared drainages. Through 26 publications (N = 127 records), 312 museum holdings, and 446 iNaturalist records, we documented 885 records pertaining to Corbicula in Mexico and shared drainages with the USA. The first record of the species in Mexico was in 1969, and it has since been reported from 26 of the 32 Mexican states and most of the major river basins throughout the country. However, we suggest Corbicula are more prevalent in Mexico than we report in this work as it is often under sampled or under reported. Resumen Algunas especies de Corbicula son de las especies invasoras acuáticas más prolíficas del mundo y pueden tener efectos negativos en los ecosistemas acuáticos. En este trabajo, realizamos estudios de campo cualitativos, examinamos literatura y registros en museos de historia natural y, además, revisamos datos de ciencia ciudadana para documentar la distribución de Corbicula en México y cuencas compartidas con EUA. A través de 26 publicaciones (N = 127 registros), 312 registros de museos y 446 registros de iNaturalist, documentamos 885 registros pertenecientes a Corbicula en México. El primer registro en México de la especie en el país data de 1969 y, desde entonces, ha J.S. Tiemann et al. / Revista Mexicana de Biodiversidad 95 (2024): e955284 2 https://doi.org/10.22201/ib.20078706e.2024.95.5284
... However, the most extensively distributed Mexican freshwater bivalve is the non-native, invasive clam Corbicula fluminea (Müller, 1774). The other two non-indigenous bivalves are Corbicula largillierti (Philippi, 1844), which has so far only been detected in Rio Conchos, in the state of Chihuahua (Tiemann et al. 2019), and Dreissena polymorpha (Pallas 1771), occurring in Río Coatzacoalcos in the state of Veracruz (Naranjo-García and Castillo-Rodríguez 2017). ...
... Recently, only two investigations dealing with conservation status of the Mexican bivalves were published. The first study was carried out by Tiemann et al. (2019) along the Conchos River, the core of the hotspot A, where the occurrence of unionid species was investigated. The authors conclude that "…the Río Conchos is currently unsuitable for mussels in most, if not all, areas" (Tiemann et al. 2019, p 184). ...
... The situation with mussels is even more dramatic. Although the hotspot A occupies a large area including the Río Conchos (750 km in length) and its tributaries, only 2 living specimens of the native mussels Utterbackia imbecillis were found during the recent study of this river by Tiemann et al. (2019). All other mussels described from this river were found only as relict shells. ...
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In this chapter, we provide an overview of the diversity of the Mexican freshwater mollusks (gastropods and bivalves). We outline their current status as one of the most imperiled group of animals in Mexico and we discuss necessary changes to stop their decline. The Mexican freshwater molluscan fauna is composed of 292 species, of which 195 are gastropods and 97 bivalves. Like many other aquatic invertebrates worldwide, members of both molluscan classes are rapidly declining in most regions of Mexico. These losses constitute a silent extinction during the Anthropocene resulting from water pollution, large diversions for irrigation of arid regions, hydropower production, and introductions of non-native species. The lack of historical data about molluscan distributions, especially of bivalves, makes it difficult to determine the full extent of these local and regional extinctions. However, a few case studies that include the methods of conservation paleobiology are used to show an alarming picture: the comparison of local sub-fossil records with recent data documents a dramatic loss of freshwater snail diversity of more than 80% in only a century. In light of this, it is becoming increasingly clear that current conservation efforts alone will not be enough to stop more extinctions. Climate change, especially increased frequency and intensity of regional drought, is known to decrease habitat quality. Dam removal along with more and larger protected areas and ecosystem restorations can reverse the trend of some of these potential species losses. We advocate a shift in consciousness so that natural scientific efforts are part of an integrated holistic solution that includes the ecological, economic, philosophical, and theological values for society.
... The most sensitive species to As and F − were Unionidae and Musculium transversum, which can be found in freshwater ecosystems in Mexico (Cózatl-Manzano and Naranjo-García, 2007;Mellado Hernandez et al., 2015;Randklev et al., 2014;Randklev et al., 2018). Notably, Unionidae are aquatic organisms that inhabit the Conchos River, where water from the Meoqui-Delicias aquifer serves as its base flow (Tiemann et al., 2020). ...
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Nearly 200 years ago, a naturalist named Rafinesque stood on the banks of the Ohio River and began to describe the freshwater mussels he found there. Since that time these animals have become the most imperiled animals in North America. Dozens of species have become extinct, and it is estimated that two-thirds of the remaining freshwater mussels face a similar fate. Yet, despite their importance, the mussels of Ohio remain a poorly documented and largely mysterious fauna. The Freshwater Mussels of Ohio by G. Thomas Watters, Michael A. Hoggarth, and David H. Stansbery brings together, for the first time, the most up-to-date research on Ohio’s mussels. Designed for the weekend naturalist and scientist alike, it synthesizes recent work on genetics, biology, and systematics into one book. Each species is illustrated to a degree not found in any other work. Full-page color plates depict shell variation, hinge detail, and beak sculpture. Full-page maps show the distribution of each species based upon the collections of numerous museums (with historical distributions dating from the 1800s). In addition to species accounts, the book has a substantive introduction that includes information on basic biology, human use, and conservation issues. Extensive synonymies, a key to all species, and an illustrated glossary are included as well.
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This well-illustrated book highlights freshwater mussels fabulous diversity, amazing array of often bizarre ecological adaptations, and their dire conservation plight. Summarizing and synthesizing historical and contemporary information as well as original research and analysis, the book describes the diverse array of mussel life history strategies and builds a cohesive narrative culminating in the development of explicit frameworks to explain pervasive patterns in mussel ecology. The fascinating and colorful role of mussels in human society is also described in detail, including the little-known pearl button industry of the early 1900s and the wild and often violent shell harvest of the 1990s. The final chapter details humans efforts to save these fascinating animals and gives a prognosis for the future of the North American fauna. The book provides the first comprehensive review of mussel ecology and conservation for scientists, natural resource professionals, students, and natural history enthusiasts.