Status of the Imperiled Frecklebelly Madtom, Noturus
munitus (Siluriformes: Ictaluridae): A Review of Data from
Field Surveys, Museum Records, and the Literature
Micah G. Bennett, Bernard R. Kuhajda, and J. Heath Howell
Southeastern Naturalist, Volume 7, Number 3 (2008): 459–474
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2008 SOUTHEASTERN NATURALIST 7(3):459–474
Status of the Imperiled Frecklebelly Madtom, Noturus
munitus (Siluriformes: Ictaluridae): A Review of Data from
Field Surveys, Museum Records, and the Literature
Micah G. Bennett1,2,*, Bernard R. Kuhajda1, and J. Heath Howell1
Abstract – Noturus munitus (Frecklebelly Madtom), is a diminutive catfish restricted
to large rivers in the Mobile Basin and Pearl River drainages in the southeastern
United States. We conducted surveys of 13 major tributaries of the Alabama, Cahaba,
and Tombigbee river systems in the Mobile Basin to determine use of tributaries
by N. munitus. Our surveys found only one specimen in Oakmulgee Creek, a large
tributary to the Cahaba River and one of the few rivers in which stable populations
of N. munitus remain. We combine results from our recent survey with a review of
the literature and museum records for N. munitus throughout its range to present a
consolidated status report. Our review indicates that N. munitus is currently greatly
reduced from its former range, and is in decline in most of the drainages it still inhabits.
We recommend federal protection for the species under the Endangered Species
Act. We also provide suggestions for future research and management actions for
Madtoms (genus Noturus) are a group of diminutive catfishes endemic
to North America, with over 50% of the 29 described species considered
imperiled and with eight or more undescribed forms (Burr and Stoeckel
1999, Thomas and Burr 2004, Warren et al. 2000). One of these species
is Noturus munitus Suttkus and Taylor (Frecklebelly Madtom), a boldly
patterned, robust madtom with a disjunct distribution in the Pearl River
drainage and the Mobile Basin (upper Tombigbee, Cahaba, and upper
Coosa river drainages) (Fig. 1; Supplementary Table 1, available only
online at http://dx.doi.org/10.1656/S593.s1; Boschung and Mayden
2004; Warren et al. 2000). Noturus munitus is usually found over gravel
shoals in large and medium-sized rivers. Since its description (Suttkus and
Taylor 1965), N. munitus has received some attention from researchers,
with aspects of diet and reproductive condition having been examined to
varying degrees (e.g., Miller 1984, Trauth et al. 1981), but no substantial
life-history study has been conducted. This lack of data is likely due to
the fish’s patchy distribution and the difficulty of sampling its preferred
large-river habitat. Noturus munitus was once a candidate species for federal
protection, but has not been reconsidered since Stewart’s (1989) status
1University of Alabama Ichthyological Collection, Department of Biological Sciences,
Box 870345, Tuscaloosa, AL 35487-0345. 2Current address - Department of
Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103-2010.
*Corresponding author - email@example.com.
460 Southeastern Naturalist Vol.7, No. 3
review recommended no federal protection at that time. While there is little
peer-reviewed literature concerning the species, there have been several
surveys conducted throughout its range since the federal review in the late
1980s. Herein we: 1) synthesize results from surveys for N. munitus from
peer-reviewed literature, government and other unpublished reports, and
museum records, 2) provide data from our recent surveys for N. munitus in
the Alabama, Cahaba and Tombigbee river drainages, and 3) give suggestions
for protection, management actions, and future research.
Several surveys for N. munitus have been conducted in the last decade,
but most have not been published in peer-reviewed literature. Herein we
present up-to-date and consolidated information on the status of N. munitus
across its range, providing summaries of five field studies of N. munitus from
both peer-reviewed journals and unpublished reports. We also compiled museum
collection data from Auburn University (AU), Tulane University (TU),
University of Alabama Ichthyological Collection (UAIC), and University
of Florida (UF) databases to qualitatively examine relative historical and
recent abundances (Table 1; Supplementary Table 1, available only online
Figure 1. Collections of Noturus munitus (Frecklebelly Madtom) based on museum
and survey records. Open circles = collections from 1950 to 1980. Filled triangles =
collections from 1981 to present.
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 461
Table 1. Number of collections containing Noturus munitus over time based on museum records from Tulane University (TU) and the University of Alabama
Ichthyological Collection (UAIC) at selected sites for which multiple records across decades were available. NC = no collections.
Number of collections with N. munitus (specimens)
River System Museum Locality 1960–70 1971–80 1981–90 1991–Present
Alabama TU Alabama River at Wilcox Bar 2 of 24 (8) 0 of 35 0 of 33 0 of 35
Alabama River at Evans Upper Bar 1 of 27 (1) 0 of 33 0 of 34 0 of 38
Alabama River at Ohio Bar 1 of 7 (5) NC NC 0 of 1
Alabama River at Stein Island 3 of 11 (20) 0 of 9 0 of 8 0 of 12
Alabama River at Taits Bar 1 of 24 (8) 0 of 34 0 of 33 0 of 25
Alabama River at Yellow Jacket Bar 2 of 25 (7) 0 of 35 0 of 31 0 of 52
Upper Tombigbee TU Tombigbee River, 9 mi NW Columbus near Hwy 50 7 of 12 (826) 0 of 1 NC NC
UAIC Tombigbee River near Vienna 2 of 4 (28) 3 of 6 (104) 0 of 4 NC
Sipsey River at US Hwy 82 0 of 12 1 of 8 (2) 1 of 10 (1) 0 of 8
Buttahatchie River near mouth 0 of 1 0 of 2 0 of 1 2 of 3 (7)
Bull Mountain Creek 0 of 1 1 of 3 (4) 0 of 3 0 of 1
Cahaba TU Cahaba River near Hwy 183/14 4 of 9 (21) NC NC 0 of 2
Cahaba River near Centreville 0 of 3 0 of 1 1 of 2 (1) NC
UAIC Cahaba River near Hwy 183/14 NC 1 of 3 (1) 1 of 9 (1) 15 of 23 (220)
Cahaba River at US Hwy 82 0 of 2 NC 0 of 6 6 of 19 (8)
462 Southeastern Naturalist Vol.7, No. 3
From summer 2006 to spring 2007, we sampled six tributaries to the
Alabama River in addition to a main channel site, three tributaries to the
Cahaba River, and four to the Tombigbee River (Fig. 2, Table 2). Sample
sites were selected based on drainage area (e.g., we chose the three largest
Coastal Plain tributaries to the Cahaba River), presence of frequently cooccurring
species (e.g., Crystallaria asprella (Jordan) [Crystal Darter]),
and potential for gravel substrates based on previous known collections.
All collections were made at night using a mesh seine (4.6 x 1.2 m or 3.0
x 1.2 m) and backpack electrofishing unit.
Figure 2. Localities of 14 sampling sites for our 2006–2007 survey of Noturus munitus
(Frecklebelly Madtom) in tributaries of large rivers in the Mobile Basin in central
and west-central Alabama and extreme eastern Mississippi. Black triangles = absent.
Gray square = present (Oakmulgee Creek).
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 463
Table 2. River specialist fish species and substrate composition at tributaries surveyed from summer 2006 to spring 2007. Sampling site codes: 1= Alabama River
at Gardiner Island; 2 = Little Mulberry Creek; 3 = Pine Barren Creek; 4 = Pursley Creek; 5 = Cedar Creek; 6 = Bogue Chitto Creek; 7 = Mulberry Creek; 8 =
Oakmulgee Creek; 9 = Affonee Creek; 10 = Haysop Creek; 11 = Sipsey Creek; 12 = Bull Mountain Creek; 13 = Yellow Creek; 14 = Coal Fire Creek. Substrate
type listed in order of predominance. Substrate codes: Be = bedrock; C = cobble; Ch = chalk; De = detritus; G = gravel; M = mud; S = sand; Si = silt.
Alabama River Cahaba River Upper Tombigbee River
Site 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Macrhybopsis sp. cf. aestivalis X X X X
(Giard) (Speckled Chub)
M. storeriana X X X X
(Kirtland) (Silver Chub)
Notropis atherinoides X X X X X
Rafinesque (Emerald Shiner)
N. uranoscopus X X
Suttkus (Skygazer Shiner)
Carpiodes velifer X X X X
(Rafinesque) (Highfin Carpsucker)
Noturus munitus X
Crystallaria asprella X X X X
Percina lenticula X
P. vigil X X X X X X
(Hay) (Saddleback Darter)
Substrate G, S G, S Be, S, G, S, S, G, Ch, Be G, S, G, S, S, M, S, M, G, S, Be, S, G, S, G, S,
C, G Si Si,C Ch, Be Si De De M Si, C, G M M
464 Southeastern Naturalist Vol.7, No. 3
Piller et al. (2004): Spring–Fall 1999, Pearl River. Piller and colleagues
(2004) surveyed 53 historic collection sites for N. munitus in the main stem
of the Pearl River as well as its tributaries (Fig. 1). No madtoms were found
in the main channel, and only 13 specimens were found at eight sites in thirdand
fourth-order tributaries. These low numbers show significant declines
in the abundance and range of N. munitus due to human-induced changes
(e.g., channelization, impoundment) that have altered fl ow regimes, channel
morphology, and substrate composition in the river.
Shepard et al. 1997: Summer–Fall, 1995–1997, Mobile Basin. Shepard
et al. (1997) conducted one of the most extensive surveys of N. munitus in
the Mobile Basin. They sampled at 113 sites, including the upper Tombigbee
(67), Cahaba (42), Alabama (6), and upper Coosa (29) river drainages from
1995 to 1997, and collected the species at 47 sites, with over half of these
from the Cahaba River.
In the upper Tombigbee River drainage, Shepard et al. (1997) collected
N. munitus at one site in the Sipsey River (4 specimens, mean catch-per-hour
= 5.33), two sites in Luxapallila Creek near its mouth (21 specimens, mean
catch-per-hour=1.09), and seven sites in the Buttahatchee River (62 specimens,
mean catch-per-hour = 8.5). Shepherd et al. (1997) admit that more
collections in the Sipsey River targeting N. munitus are needed, as its fl oodprone
watershed makes sampling difficult, and the species is undoubtedly
more common than their data indicate. The Buttahatchee River is clearly
the stronghold for N. munitus in the system. Several historic sites for the
madtom in tributaries throughout the upper Tombigbee River produced no
specimens (e.g., Sipsey Creek, Bull Mountain Creek). In addition, Luxapallila
Creek has been severely affected by channelization, and no specimens
were collected at several sites upstream of the mouth.
Shepard et al. (1997) made six collections on the main channel of Alabama
River, but these produced no specimens. Only one of the gravel islands appeared
potentially suitable (Wilcox Bar), but the fish abundance and diversity
at the site was poor. They concluded that the species was likely extirpated from
the system, and no surveys since have contradicted this finding.
On the Cahaba River, Shepard et al. (1997) collected N. munitus at 27
of 42 sites. Downstream of the Fall Line, the species was fairly common on
gravel bars with suitable stable substrates down to about five miles below the
confl uence of Oakmulgee Creek, with catch-per-hour values ranging from
2 to 36 individuals/hour (mean = 11.5). Suitable habitat thus appears to be
quite common in the Cahaba River, and the drainage stands out as one of the
few areas in which N. munitus is still abundant.
In the Etowah River, Shepard et al. (1997) made collections at 19 sites
in the main stem, with N. munitus found at nine localities, and obtained data
from University of Georgia researchers on another five localities for a total
of 14 sites at which N. munitus was found. Their collection data showed N.
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 465
munitus to be fairly abundant upstream of Allatoona Reservoir up to the
more montane regions of the drainage in Lumpkin County, GA, with several
high catch-per-hour values (range = 2–24, mean = 7.6).
Shepard et al. (1997) failed to collect any N. munitus at the six sites (nine
collections) they sampled in the Conasauga River. While they did find suitable
habitat for N. munitus at three sites, and the fauna included federally
listed species such as the Cyprinella caerulea (Jordan) (Blue Shiner), and
Percina antesella Williams and Etnier (Amber Darter), no N. munitus were
found. Several historic sites had been severely degraded by sedimentation
and no suitable habitat remained at those sites.
Millican et al. (2006): Summer 2002–2005, Upper Tombigbee River.
From 2002 to 2005, Millican et al. (2006) conducted extensive surveys of
the Tombigbee River system, including all the tributaries in Mississippi in
which N. munitus had previously been documented. Of 104 sampling sites,
N. munitus was found at only 10 sites in the system, restricted to three areas:
Luxapallila Creek (three sites), the Buttahatchee River (two sites), and the
East Fork of the Tombigbee River (five sites). The total number of individuals
collected over three years was only 18, and the average abundance per
site where present was two individuals. These three streams were characterized
by Millican et al. (2006) as having a relatively high proportion of gravel
substrate (0.5–0.9) and a relatively low proportion of sand substrate (0.0–
0.4) in their most distal portions from the Tennessee-Tombigbee Waterway.
This recent survey of one of the most historically important systems for N.
munitus documents the dramatic decline of the species in the main channel
of the Tombigbee River since the construction of the Waterway (Boschung
1989). While the species persists in a small area of the former main channel
(East Fork), it has been greatly reduced from its former range in the system
Freeman et al. (2003): 1998–2002, Upper Coosa River. Freeman et al.
(2003) analyzed the historic distribution of N. munitus in the Conasauga and
Etowah river drainages and conducted surveys for the fish at 10 shoals in the
upper Etowah River to examine habitat associations. Noturus munitus was
collected at all 10 sites and was statistically associated with shallow (<50
cm), fast-fl owing riffl e areas with Podostemum spp. (riverweed) and moveable
substrate. Analysis of historical collections showed that the species is
historically rare in the Etowah River, with 66 of the 97 collections containing
fewer than 10 individuals, and is restricted to the main stem of the Etowah
and lower portions of Amicalola Creek. In the Conasauga River, historic
collections revealed only 13 sites (with 24 collections) at which N. munitus
has been collected, restricted to the main stem of the river. In all except one
collection, fewer than four individuals were collected. Records from the
Georgia–Tennessee border are from 1969 and 1970, and repeated sampling
since then has not produced additional specimens.
Freeman et al. (2005): 1997–2005, Conasauga River. Freeman et al.
(2005) conducted surveys of the Conasauga River from 1998 to 2005 as
466 Southeastern Naturalist Vol.7, No. 3
part of a study mapping critical habitats in the drainage at 20 shoals on the
river. Their study found N. munitus at about half the sites from 1997 to 1999;
however, after 1999, no individuals were collected at any of the sites. They
concluded that N. munitus is extirpated from the Conasauga River upstream
of US/GA Highway 76/52, but its status below the bridge crossing is unknown.
Noturus munitus has not been collected from the Conasauga River
since 2000, and its status in the drainage is precarious.
The results of our compilation of museum records reveal the same history
of decline for N. munitus throughout its range as the above studies. In
the four museum databases we examined, 134 collections of N. munitus
were made from 1957 to 2007 (Supplementary Table 1, available only
online at http://dx.doi.org/10.1656/S593.s1). Several collections from the
Upper Tombigbee River contained more than 300 individuals before construction
of the Tennessee-Tombigbee Waterway; however, based on the
data we examined, the last specimens were collected in the main channel in
1980 (although N. munitus persists in a small section of the East Fork of the
main channel; Millican et al. 2006, see above). While some collections did
contain several hundred individuals, the majority of collections contained
fewer than 20 specimens. Noturus munitus was found in only 7 sites in the
Alabama River, and only 50 specimens were reported in museum data. A
total of 344 individuals were collected in the Cahaba River drainage at about
18 sites. The most individuals (2305) and sites (35) were found in the Upper
Tombigbee River drainage. The Upper Coosa River drainage (Conasauga
and Etowah rivers) contained 126 specimens at 16 sites. Time-series data
shows a dramatic decline in numbers of collections of N. munitus at historic
sites in both the Alabama and Upper Tombigbee rivers, contrasting with the
persistence of collections in the Cahaba and Buttahatchee rivers containing
N. munitus (Table 1).
Field survey: summer 2006–spring 2007
In October 2005, we collected a single specimen of N. munitus in Oakmulgee
Creek, the largest Coastal Plain tributary to the Cahaba River, more
than three kilometers from its mouth. This finding prompted us to conduct a
survey of large Mobile Basin tributaries in the upper Tombigbee, Alabama,
and Cahaba rivers in central and west Alabama and extreme eastern Mississippi
(Fig. 2) to determine how frequently N. munitus utilizes tributary
habitat and if it might thereby persist in the Alabama River system. While
we did collect several fish that are large-river specialists and found suitable
gravel substrate in a few tributaries (Table 2), no N. munitus were collected
in our study sites in the Alabama and Upper Tombigbee river drainages. The
gravel substrate on Gardiner Island in the Alabama River was imbedded, and
inappropriate for N. munitus, and water levels varied greatly during the few
hours we sampled due to fl ow modifications from the reservoir downstream.
Several of the creeks in the upper Tombigbee River system had apparently
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 467
experienced recent severe head cutting and suitable gravel substrate was no
longer available. Sampling in other large Cahaba River tributaries failed to
produce additional specimens. The results of this recent survey conducted
for N. munitus confirms the conclusions of Shepard et al. (1997) and Shepard
(2004) that the species is likely extirpated from the Alabama River. In
addition, our findings highlight the lack of suitable habitat in several river
drainages and the necessity of stable large-river gravel habitat for persistence
of the species. Tributaries and their junctions with main river channels
may provide suitable habitat for waifs when there is a healthy population in
the main channel; however, tributary habitat is apparently not suitable for
sustaining viable populations of N. munitus. This scenario seems to be the
case from our data in the Cahaba River, where Oakmulgee Creek provides
habitat for waifs, but does not support any sizeable population.
Noturus munitus was once fairly abundant in appropriate habitat
throughout its range, with night-time collections on large-river gravel
shoals before the late 1960s regularly producing large collections of specimens
in the hundreds (Supplementary Table 1, available only online at
http://dx.doi.org/10.1656/S593.s1; Piller et al. 2004). One of the most
extensive analyses of historic population trends was conducted by Piller et
al. (2004) using museum collection data from the Pearl River from 1950 to
1988. They found a precipitous decline in the N. munitus population in the
Pearl River after 1964, coinciding with many human-induced river modifications,
despite the fact that sampling effort (number of samples per year)
was higher after 1964. While this study focused only on the Pearl River, the
same decline in abundance of N. munitus associated with river modification
has occurred across its range, as the surveys discussed above document.
Examination of available museum records reveals a similar pattern in the
Alabama and Tombigbee rivers (Table 1), with few collections after 1970
producing specimens, in contrast to the Cahaba River collections, in which
N. munitus seems to have remained fairly common. While these museum
datasets undoubtedly omit some records, a general trend similar to the findings
of Piller et al. (2004) is apparent.
Construction of the Tennessee-Tombigbee Waterway, which artificially
connects the Tennessee River to the Gulf of Mexico through the Tombigbee
River with 10 lock and dam structures, began in 1972 and has greatly affected
the ecology of the river system, including the probable extirpation of
N. munitus and other aquatic organisms from the majority of the main river
channel (Boschung 1989, Millican et al. 2006, Roberts et al. 2007, Shepard
2004). Three dams were constructed on the Alabama River in late 1960s
and early 1970s, which contributed to the likely extirpation of N. munitus
from this river (Boschung and Mayden 2004, Shepard 2004, Shepard et al.
1997). There is one dam on the Etowah River forming the Allatoona Reservoir,
which has likely affected N. munitus, but the species persists in low
468 Southeastern Naturalist Vol.7, No. 3
numbers upstream of the reservoir. The Cahaba River, Conasauga River,
and some tributaries to the upper Tombigbee River are the only remaining
waters within the range of N. munitus that have escaped large-scale human
modification through damming or channelization. However, populations
in the Conasauga River are greatly reduced from their former extent and
perhaps extirpated in the drainage, having been heavily impacted by poor
land-use practices in the surrounding watershed (Shepard 2004, Shepard
et al. 1997), and the species has not been seen in the drainage since 2000
(Freeman et al. 2005). Tributaries to the upper Tombigbee River have been
affected by channel modification of the Tennessee-Tombigee Waterway due
to head cutting and other geomorphic and fl ow modifications (e.g., Raborn
and Schramm 2003, Roberts et al. 2007, Tipton et al. 2004), and only a few
tributaries maintain necessary habitat for N. munitus in this system (Sipsey
and Buttahatchee rivers, East Fork of the Tombigbee River, and Luxapallila
Creek; Millican et al. 2006, Shepard 2004, Shepard et al. 1997). In the Cahaba
River, N. munitus abundances seem to have remained stable throughout
the modification periods in surrounding drainages, with the species being
common and abundant below the Fall Line to about 20 km above the junction
with the Alabama River (Table 1; Supplementary Table 1, available only
online at http://dx.doi.org/10.1656/S593.s1; Shepard et al. 1997). However,
channel geomorphology and substrate in the Cahaba River is likely being
affected by head cutting due to impoundment of the Alabama River, similar
to changes occurring in the upper Tombigbee River.
Based on our recent field observations, we hypothesize that, in normally
functioning systems, tributaries serve as habitats for population sinks as
compared to the source populations of N. munitus in main river channels
(Pulliam 1988). Many of the tributaries we surveyed contained several
large-river specialist fishes (Table 2) with similar dietary and habitat requirements
as N. munitus (e.g., C. asprella, Percina lenticula Richards and Knapp
[Freckled Darter]). Roberts et al. (2007) found a high degree of dietary
plasticity that helped allow C. asprella to persist in the heavily modified
Tennessee-Tombigbee Waterway and hypothesized that tributary junctions
serve as post-modification source habitats for C. asprella population sinks
in the main channel. Madtoms, like darters, are prey generalists (Burr and
Stoeckel 1999) and would likely exhibit similar plasticity in the face of
river modification. However, since it appears that N. munitus cannot adapt
to persist in the main channel after modification, tributaries cease to serve as
habitat, either as sources or sinks. Differences in reproductive biology (i.e.,
nesting in madtoms) are likely causes for the different responses to modification.
Suitable nest cavities are probably naturally uncommon in large Coastal
Plain-river gravel shoals, and the most likely candidates for nest sites are
empty mussel shells and woody debris. Channelization and other river modifications cause mussel decline (Brainwood et al. 2006, Neves and Williams
1994) and also remove woody debris through dredging and “de-snagging”
(Shields and Smith 1992), making the two sources for nesting sites for N.
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 469
munitus even rarer. Since cavity nesting in madtoms appears to result from
historical evolutionary constraints (Burr and Stoeckel 1999), adaptation to
different modes of reproduction is unlikely. More study is needed on other
specific aspects of biology that contribute to different responses to river
To further complicate conservation and the analysis of impacts, there appears
to be some cryptic diversity within what is currently described as N.
munitus. Populations in the upper Coosa River system in the Conasauga and
Etowah rivers are morphologically distinct and widely considered a separate
undescribed species (Boschung and Mayden 2004, Shepherd 2004, Warren
et al. 2000). The upper Coosa River form is apparently in more rapid decline
than other populations, but its protection is somewhat inhibited by lack of
specific recognition (Butler and Mayden 2003).
Thus, N. munitus has been extirpated from one of the drainages in which
it was found (Alabama), has been greatly reduced in three other drainages
(Pearl, upper Tombigbee, and upper Coosa), and occurs at high numbers
drainage-wide in only one river (Cahaba) (Fig. 1).
Conservation and future research needs
The lack of published information on the genetic and morphological
variation and population structure within N. munitus populations should be
remedied. Without formal recognition of cryptic biodiversity within what is
potentially a species complex, the evolutionary diversity within N. munitus
may not be preserved. While the species as currently described meets federal
listing criteria as threatened due to widespread habitat loss and decline, its
broad range has been a rationale for denying protection in the past (Stewart
1989). Without a better understanding of historic and current gene fl ow and
divergence in N. munitus—both within and among major river drainages—
the species cannot be adequately managed for and conserved.
More information is also needed on spawning and nesting habitat. While
certain conclusions and inferences can be drawn from our current knowledge
of madtom biology, nesting habitat is quite variable among Noturus species,
and there is no substitute for visual documentation of spawning habitat and
season duration (Burr and Stoeckel 1999). Additionally, attempts to infer
nesting biology from sister species based on phylogeny (such as N. stigmosus
Taylor [Northern Madtom], and N. placidus Taylor [Neosho Madtom];
Hardman 2004, Near and Hardman 2006) are hindered due to lack of data for
those species as well (Burr and Stoeckel 1999).
Finally, the potential for restoration of degraded river habitat and reintroduction
of N. munitus should be rigorously assessed. Removal of large
dams is being increasingly considered in an effort to restore river ecosystem
function, but remains highly controversial (Bednarek 2001, Born et al. 1998,
Poff and Hart 2002, Stanley and Doyle 2003). While dam removal has the
potential to restore ecosystem function through a return of biological (e.g.,
species dispersal/migration), chemical (e.g., nutrient transport) and physical
(e.g., sediment transport, fl ow regime) processes (Bednarek 2001, Hart et
470 Southeastern Naturalist Vol.7, No. 3
al. 2002), dam removal constitutes a severe disturbance to the aquatic community,
the magnitude of which will vary depending on the size of the dam,
the length of time the dam has been in place, and the composition of the
local biotic community, among other factors (Poff and Hart 2002, Stanley
and Doyle 2003). In addition, removal of large dams may not be politically
or economically feasible in some instances due to lack of public support and
loss of public services such as hydroelectric power or public water supply
(Poff and Hart 2002, Whitelaw and Macmullan 2002). Therefore, until more
data is gathered on dam removal and it garners wider support, efforts should
be focused on restoration of historic fl ow regime within the current framework
of dams, as has been done for some large-river fishes such as Acipenser
fulvescens Rafinesque (Lake Sturgeon) (Auer 1996). While this management
option comes with its own uncertainty, and should be rigorously evaluated
(Irwin and Freeman 2002), dam mitigation, in which modifications are made
to increase or vary minimum fl ow from dams to mimic natural conditions,
has been shown to improve aquatic insect communities impacted by these
structures (Bednarek and Hart 2005) and has potential to restore or maintain
more natural fish assemblages (Irwin and Freeman 2002).
Reintroduction of aquatic organisms is also controversial and is often
only limitedly successful (Stockwell and Leberg 2002, but see Shute et al.
2005). Inappropriate selection of location and sizes of source populations
which fails to consider local adaptation and allelic diversity can destroy
co-adapted gene complexes at reintroduction sites where some native individuals
remain (outbreeding depression), and inadequate size or genetic
variability in source populations can cause inbreeding depression, all of
which increase human-induced decline of the species of concern (Leberg
1993, Meffe and Vrijenhoek 1988, Stockwell and Leberg 2002, Templeton
et al. 2000). In the case of N. munitus, if the Alabama River is ever restored
to any extent, the Cahaba River is the best choice for a source population
due to replicated patterns of similarity in fish faunas (both genetically and
in community structure) between the Cahaba and Alabama rivers, likely the
result of close proximity and similarities in underlying geology (Boschung
and Mayden 2004). Individuals from other drainages should not be used to
supplement populations in the upper Coosa River because these populations
are certainly distinct (Butler and Mayden 2003, Shepherd 2004). If reintroduction
of N. munitus is ever attempted, it should be undertaken with the
above considerations in mind.
In our assessment based on recent surveys, N. munitus warrants federal
protection as a threatened species. While it remains widely distributed across
the southeastern US, it has declined precipitously from historic abundance
since the late 1960s and is currently found in abundance in only the Cahaba
and Buttahatchee rivers. Further, its dependence on large-river gravel shoal
habitat makes it vulnerable to river modification that will likely continue
into the foreseeable future. The Endangered Species Act (ESA) has been
widely criticized by scientists and policy-makers for more than a decade as
2008 M.G. Bennett, B.R. Kuhajda, and J.H. Howell 471
insufficient for species protection and recovery (Gibbons 1992, National Research
Council 1995, Scott et al. 2005). While there may indeed be problems
with the legislation, current data and methods used in evaluating species
recovery may be inadequate, thus underestimating success (Bain et al. 2007,
Campbell et al. 2002, Gerber and Hatch 2002, Male and Bean 2005). A recent
study documenting the remarkable recovery of Acipenser brevirostrum
Lesueur (Shortnose Sturgeon) in the Hudson River shows that the ESA, with
its combination of species and habitat protection and public involvement
fully realized, has potential to effect recovery of species under its purview
(Bain et al. 2007). Even with its potential shortcomings, the ESA offers the
strongest existing enforceable protection against extinction and provides
a framework for recovery for N. munitus. Conservation of N. munitus will
depend upon our willingness to preserve the few remaining free-fl owing rivers
in its range, our effectiveness as scientists to promote conservation and
appreciation of such aquatic systems, and our ability to gain the necessary
understanding and knowledge to do both.
Much-needed field assistance on our field surveys was provided by B.L. Fluker
and J. Chesser. We thank C. Taylor, T. Shepard, and B. Albanese for access to
unpublished reports. Comments by Guest Editor James Albert and two anonymous
reviewers greatly improved the manuscript. This research was supported by a grant
from the Walter F. Coxe Research Fund (Birmingham Audubon Society) to M.G.
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