2008 SOUTHEASTERN NATURALIST 7(4):665–678
Density Dynamics of a Threatened Species of Darter at
Spatial and Temporal Scales
Mitchell S. Wine1, Michael R. Weston2, and Ronald L. Johnson2,*
Abstract - Etheostoma moorei (Yellowcheek Darter), a candidate species for federal
listing, is endemic and obligate to headwater riffles of the upper Little Red River
drainage in north central Arkansas. Downstream segments of these tributaries were
inundated in 1964 as a result of filling of Greers Ferry Reservoir. We compared
riffle densities during drought (1999–2001) and non-drought periods (2003–2004),
and to historic data (1979–1980). Upstream sites dried periodically during the
drought of 1999–2001, and Yellowcheek Darters occupying those sites were extirpated;
even at downstream sites, densities were significantly lower than historical
levels. During normal precipitation levels during 2003–2004, densities increased
significantly, yet several upstream sites and one complete stream remained extirpated.
The loss of downstream refugia as a result of the construction of Greers
Ferry Dam in 1964 may exacerbate natural climatic cycles, which include drought,
resulting in stream-wide extirpations.
Etheostoma moorei Raney and Suttkus (Yellowcheek Darter), with a
maximum standard length of 64 mm (Robison and Buchanan 1988), is one
of only two members of the subgenus Nothonotus known to occur west of
the Mississippi River (Wood 1996). First collected in 1959 from Devils
Fork of the Little Red River of north-central Arkansas (Raney and Suttkus
1964), much of the Yellowcheek Darter’s range was inundated in 1964 when
Greers Ferry Dam was completed (Robison and Buchanan 1988). Raney
and Suttkus (1964) suggested that the remaining upstream reaches of the
four headwater streams (Archey, Middle, South, and Turkey/Beech/Devils
forks) would serve as Yellowcheek Darter sanctuaries. Sympatric darter species
common to the Little Red River drainage system include E. caeruleum
Storer (Rainbow Darter), E. blennoides Rafinesque (Greenside Darter), and
E. zonale Cope (Banded Darter) (Wine 2004).
A 1979–1980 status survey indicated the Yellowcheek Darter to be the
most abundant riffl e fish within its range (McDaniel 1984, Robison and Harp
1981). Robison and Harp (1981) estimated a total population for the four
headwater streams of ca. 60,000 individuals. However, during a later study
of the genetic structure of Yellowcheek Darter populations in 1998, Mitchell
et al. (2002) observed individuals to be rare at several sites where they were
1US Fish and Wildlife Service, Arkansas Ecological Services Field Office, 110 South
Amity Road, Suite 300, Conway, AR 72032. 2Arkansas State University, Department
of Biological Sciences, State University, AR 72467. *Corresponding author - rlj@
666 Southeastern Naturalist Vol. 7, No. 4
previously abundant (McDaniel 1984). For example, only one individual
was captured during four hours of kick seining in Beech Fork. During sampling
by Mitchell et al. (2002), there was a severe drought for several years
(NCDC 2007), and several of the sites previously inhabited by Yellowcheek
Darters were dry during portions of the year.
Currently, the Yellowcheek Darter is a candidate species for listing
under the Endangered Species Act of 1973, as amended (Federal Register
2001). Other than the original species description (Raney and Suttkus
1964), published literature regarding this species is limited to genetic
analyses (Johnson et al. 2006b, Mitchell et al. 2002, Wood 1996). Reductions
in abundance, the prolonged drought during the 1990s and this void
of ecological literature led to the present study. The goal of this study was
to compare current to historic densities of Yellowcheek Darters in the headwater
streams of the Little Red River in the context of variable hydrology.
We were particularly interested in recolonization of upstream sites that had
recently and periodically dewatered.
The Middle Fork (MF) is the largest Little Red River tributary. Elevation
of the streambed declines an average 2.8 m/km (0.28% gradient)
along the 65 km of the Middle Fork known historically to support Yellowcheek
Darters (McDaniel 1984). The Middle Fork is a third-order stream
at the uppermost sample site (MFA) and a fifth-order stream at the lowest
sample site (MFD). The South Fork (SF) is the second largest tributary,
with a gradient of 0.17% along the 24-km study reach. It is a secondorder
stream at the uppermost study site (SFA) and third-order stream
at the lowest site (SFC). The Archey Fork is a third-order stream with a
gradient of 0.14% along 18 km. Turkey, Beech, and Devils forks are confluent
streams, with Turkey Fork representing the uppermost segment and
Devils Fork the lowest. This watershed has the steepest stream gradient at
0.30% along 25 km (McDaniel 1984). The upstream site (TF) is a secondorder
stream, whereas the downstream site (BF) is a third-order stream.
The watersheds of these headwater streams are steep, with relatively
impermeable soils that contribute to rapid changes in water levels during
and following precipitation events.
The 1999–2001 surveys were conducted during an extended drought with
reduced stream fl ow, and the surveys during 2003–2004 were performed
during a time of normal stream fl ow to determine and compare Yellowcheek
Darter densities during differing fl ow regimes. Eleven riffl e sites were chosen
due to their historic Yellowcheek Darter populations (Robison and Harp
1981) and availability of access. These sites were surveyed between August
1999 and November 2001, and seven of those eleven sites were surveyed
2008 M.S. Wine, M.R. Weston, and R.L. Johnson 667
from August 2003 through September 2004. The eleven initial sites included
four sites on Middle Fork (MFA, B, C, and D), three sites on South Fork
(SFA, B, and C), two sites on Archey Fork (AFA and B) and one site each on
Turkey (TF) and Beech (BF) forks (Fig. 1). Each site was 0.8 km in length
and the number of riffl es surveyed at each site ranged from two to four.
These sites coincided with and were directly compared to three sites used in
the 1979–1980 survey (MFD, SFA, BF; McDaniel 1984, Robison and Harp
1981). The seven sites sampled during 2003–2004 were MFA–D, SFA, SFC,
and TF, with two sites (MFD, SFA) compared to historical data. During the
latter study, we focused on the Middle and South Forks (although we had no
access to SFB), due to their supporting the greatest numbers of individuals.
Uppermost and lowest sites for each stream represent the extreme limits of
Yellowcheek Darter distributions (Robison and Harp 1981, McDaniel 1984,
Mitchell et al. 2002). Downstream of these riffl e sites, the substrate was primarily
composed of bedrock. Additionally, streambanks upstream of MFA
were characterized by high erosion.
Adult Yellowcheek Darters (>30 mm) and sympatric species were collected
using a kick-seine method (surface area of 1.5 m2 with 0.48-cm mesh
size). Sampling began at the downstream end of riffl es and progressed upstream,
with sampling involving ≥50% of the riffl e surface area. The number
of sets was recorded and mean fish density for each riffl e was determined
by dividing the number of fish collected by the surface area sampled. Each
study site was sampled and densities were estimated several times during
1999–2001 and again in 2003–2004 (see Table 1 for sampling frequency).
Figure 1. Etheostoma moorei (Yellowcheek Darter) study sites on tributaries of the
Little Red River in Arkansas.
668 Southeastern Naturalist Vol. 7, No. 4
Lastly, abundance of this darter relative to other sympatric species was
compared for 1999–2001 versus 1979–1980, to determine if abundance differences
were a species versus an assemblage phenomenon.
Kick seining proved to be the most effective non-lethal method of collecting
darters. Although snorkeling has commonly been used in the study
of darters (e.g., Chipps et al. 1994, Greenberg 1991, Stauffer et al. 1996),
snorkeling proved ineffective at our sites, due partly to the crevice-dwelling
behavior of the Yellowcheek Darter and partly to stream fl ow conditions
usually being prohibitively low or high for snorkeling.
Sampling efficiency of darters in headwater streams has been estimated
at between 50–60% (Peterson and Rabeni 2001), which is impacted by the
variables of substrate and flow (Fisher 1987, Peterson and Rabeni 2001).
Electrofishing (Backpack Model 15 D Smith-Root, Inc.) was therefore conducted
to validate the accuracy of the kick seine method and develop conversion
factors for estimating densities. For example, one riffle each within
MFC and SFC was block-netted at upstream and downstream margins and
measured. Fifty percent of the riffle area was sampled using the kick-seine
method, and Yellowcheek Darter density was estimated. The entire riffle
was then electrofished using the three-pass sum-of-catches depletion method
(Riley and Fausch 1992) to determine a second density estimate. During
shocking passes, the substrate was agitated to dislodge shocked specimens,
which were then collected and put in five-gallon buckets for later identification
and enumeration. Dividing the electrofishing estimate by the kickseine
estimate produced the respective conversion factor. In each case,
kick-seine estimates were multiplied by their respective conversion factors
(1.35 for the Middle and Beech forks, 2.88 for the South and Archey forks)
to produce a density estimate for each sample site.
Table 1. Comparisons of estimates of mean Yellowcheek Darter densities (number/m2), with
95% confidence intervals, for each study site of the Little Red River, AR.
1979–1980 1999–2001 2003–2004
Site Site samples Density Site samples Density Site samples Density
A 0 N/A 9 0.05 ± 0.12 5 0.00 ± 0.00
B 0 N/A 1 0.77 4 0.24 ± 0.28
C 0 N/A 7 1.11 ± 0.79 6 1.67 ± 0.65
D 9 2.38 ± 1.13 3 0.66 ± 0.13 5 1.67 ± 0.77
A 5 1.16 ± 0.62 7 0.22 ± 0.26 6 2.09 ± 1.92
B 0 N/A 3 0.00 ± 0.00 0 N/A
C 0 N/A 7 2.06 ± 0.87 7 1.29 ± 0.34
A 0 N/A 2 0.00 ± 0.00 0 N/A
B 0 N/A 7 0.06 ± 0.10 0 N/A
Turkey Fork 0 N/A 4 0.00 ± 0.00 2 0.00 ± 0.00
Beech Fork 4 0.59 ± 0.66 5 0.47 ± 0.90 0 N/A
2008 M.S. Wine, M.R. Weston, and R.L. Johnson 669
Methods used to derive conversion factors were similar to those used by
Robison and Harp (1981), yet the conversion factor for their work (2.71) was
derived from the Middle Fork, and then applied to each of the other streams.
Although their study was also conducted during a drought, water levels were
greater (10% greater mean monthly stage height; USGS 2006), and therefore
kick-seining efficiencies were likely lower during their study than at present
(G. Harp, Arkansas State University, State University, AR, pers. comm.).
This differing application of a correction factor between studies introduces
some uncertainty in interstudy analyses.
Consistency in technique within and among researches and studies was
attempted by having G. Harp, the initial investigator of Yellowcheek Darter
distributions in the Little Red River train both M.S. Wine and M.R. Weston
on sampling technique. Wine and Weston subsequently performed all sampling
for this study, and seined only during low fl ow. Seine and mesh size
were also kept constant among sampling periods. Due to the many variables
among studies, no attempts were made to compare our density data to those
for other darter species.
Proximal downstream pool areas (n = 11) were also sampled during zerodischarge
riffl e conditions (no surface fl ow) to record pool fish assemblages
and to determine if Yellowcheek Darters used pools as refugia during periods
when riffl es were dry. Pools were isolated using block nets at upstream and
downstream margins and backpack electrofished twice. No Yellowcheek Darters
were collected in these downstream pools, nor have they been collected
from pools historically despite extensive efforts (Robison and Harp 1981).
Some riffl e species can use the hyporheic zone during riffl e drying (Berra
and Allen 1989, Gagen et al. 1998, Stegman and Minckley 1959). However,
Weston (2006) failed to find any individuals occupying pits dug into the
thalweg of MFB during riffl e drying. On the basis of these evidences, it was
determined that Yellowcheek Darters were leaving these riffl es during drying
(or dying as those riffl es dried), and therefore densities were recorded as
zero when sites were dry.
We used ANOVA to compare Yellowcheek Darter densities among sites and
streams. Downstream sites were compared among streams rather than using all
sites, as upstream sites had few individuals and low fl ow. ANOVAs demonstrating
significance were followed with Tukey’s multiple comparison a posteriori
test to investigate level interactions. Temporal differences within sites among
sampling periods (1979–1980, 1999–2001, and 2003–2004) were also compared
using ANOVA. All confidence intervals given are 95% group confidence
intervals for the difference between the two density means between sites and
streams. Alpha levels for all significance tests were set at α = 0.05.
The United States Geological Survey (USGS) maintained a gauging station
for surface water data at MFD (Gage 07075000 continuously from 1974
670 Southeastern Naturalist Vol. 7, No. 4
to 2002) and SFC (Gage 07075300 continuous through all studies). Stage
height was compared to historical data (USGS 2006), as water levels were
noticeably lower during the present study as compared to the previous study
(G. Harp, Arkansas State University, State University, AR, pers. comm.).
During the 1999–2001 sampling period, all upstream sites were periodically
dry. Discharge, thalweg velocity, and thalweg depth were measured during
1999–2001 to provide insight into site and stream differences. Velocity was
measured by an electronic fl ow probe (Model FP 101, Global Water Instruments,
Substrate composition and cobble embededness were visually evaluated
for each site on the Middle and South forks during summer (August
2004) low-fl ow conditions. Data were collected along five longitudinal
transects (upper 20%, 21–40%, 41–60%, etc.) and two to five cross-channel
transects (left, ¼, ½, ¾, and right), depending upon stream width. Along
each transect, we used a view box to estimate percent silt (<1.0 mm), sand
(1.0 mm–0.5 cm), gravel (0.5–8.0 cm), cobble (8.0–30.0 cm), boulder (>30.0
cm), and bedrock. As both species prefer gravel and cobble substrate (Mc-
Daniel 1984, Winn 1958), we focused our analyses on these two variables.
Cobble embededness was estimated as the percent silt- and/or sand-covered
or embedded cobble at these locations.
Yellowcheek Darter densities were highly variable spatially and temporally
(Table 1). Upstream sites were subject to drying early in the study.
No surface water fl ow was observed in riffl es at: MFA, SFA, TF, AFA or
AFB during August 1999; MFA, SFA, or SFB in September 1999; SFB in
November 1999; or AFB in September 2000. Densities were lower at MFD
during 1999–2001 as compared to both 1979–1980 (80% decline, but no
statistical significance, P = 0.08) and 2003–2004 (86% decline, P = 0.04)
(Table 2). Densities were also lower in 1999–2000 than in 1979–1980 at SFA
(P < 0.05). During 1999–2004, no Yellowcheek Darters were collected at TF,
SFB, or AFA, and only intermittently collected at MFA and AFB.
Yellowcheek Darter densities were similar among downstream stream
sites for all time periods studied (P range of 0.29 to 0.38; Table 1). ANOVA
did reveal significant differences in densities among sites within the Middle
Fork for both the 1999–2001 (F2,16 = 7.766, P = 0.004) and 2003–2004 periods
(F3,16 = 18.073, P < 0.001) (Table 2). A Tukey multiple comparison
a posteriori test showed that the MFA Yellowcheek Darter density (where
one individual was collected in five sampling years) was less than MFC for
1999–2001 and less than MFC and MFD for 2003–2004 (P < 0.05). MFB
Yellowcheek Darter density was also less than densities at MFC and MFD
during 2003–2004 (P < 0.05). There were no significant differences in
2008 M.S. Wine, M.R. Weston, and R.L. Johnson 671
Yellowcheek Darter densities among sites on the South Fork (1999–2001:
P = 0.06; 2003–2004: P = 0.28).
Yellowcheek Darters ranked fifth in abundance of fish collected during
1999–2001, comprising 7% of the overall sample. This represents a substantial
drop (20%) in the relative abundance of the Yellowcheek Darter, as
during 1979–1980 it was the most abundant species, comprising 27% of that
sample (Robison and Harp 1981).
Monthly stage height for both MFD and SFC during 1999–2001 sampling
was lower during late summer months than during the 1979–1980
study and also lower than the 25-year averages (Fig. 2). Upper sites in all
four tributaries, as well as the lower site in the Turkey/Beech fork system
(BF), were observed to be completely dry on at least two occasions during
the late summer months of 2000. However, during 2001–2004, the upper riffl
e sites of Middle and South forks never completely dried, although one site
(MFB) was low enough during September 2004 that no fl ow was detectable.
Water depth at that time was less than 2.5 cm across one of two MFB riffl es
studied. We identified a stage height of 1.53 m at the USGS gage station at
MFD and 1.02 m at the USGS gage station at SFC as the minimum currently
required to maintain water fl ow at the upper study sites within this system.
Stage heights below these minima result in upper riffl e sites experiencing
zero discharge. Mean monthly stage height was never below this critical
threshold in 2001–2004 (Fig. 2).
Flow on the South Fork was less than on the Middle Fork (Fig. 2). Discharge
increased downstream on the Middle and Turkey/Beech forks, yet
Table 2. Comparisons of densities of Yellowcheek Darters of the Little Red River drainage
system spatially and temporally where significance exists among levels. Where a significant difference
exists between means, the 95% confidence intervals for the difference between variables
is given (column, row). NSD = no significant difference exists for individual comparisons.
A. Spatial comparisons among Middle Fork sites; 1999–2000 comparisons on first line and
2003–2004 comparisons on second line.
MFA MFB MFC
MFB NSD - -
NSD - -
MFC (-1.761, -0.362) NSD -
(-2.486, -0.844) (-2.303, -0.552) -
MFD NSD NSD NSD
(-2.522, -0.906) (-2.336, -0.517) NSD
B. Temporal comparisons within Middle Fork and South Fork sites
MFD (2003–4) SFA (1979–81)
MFD (1999–2001) (0.071, 1.944) -
SFA (1999–2001) - (0.071, 1.944)
672 Southeastern Naturalist Vol. 7, No. 4
was largely constant within the South and Archey forks (Table 3). Stream
riffl e velocity ranged from 0.59 to 1.01 m/s, with the MFB data serving as
an outlier (MFB sampling was limited to three late summer samples only).
Depth generally increased downstream for each stream.
Substrate was mostly gravel (50%) and cobble (34%) (Table 3), with
minimal boulder (4.0%), silt (<1.0%), and bedrock (<1.0%) within sites.
There were significant differences among sites for both gravel and cobble
substrate (gravel: F3,164 = 35.936, P < 0.001; cobble: F3,164 = 37.609, P <
0.001). Gravel represented a significantly smaller percent of the substrate
composition at MFB than at MFA, MFC, and MFD (Tukey’s: P < 0.01), and
MFA had less gravel than MFD (Tukey’s: P < 0.05). Predictably, based upon
the predominance of gravel and cobble within sites and therefore an inverse
relationship between these two variables, cobble represented a significantly
greater percent of the substrate composition at MFB than at MFA, MFC, and
Figure 2. Monthly
1 9 7 9 – 1 9 8 0 ,
1 9 9 9 – 2 0 0 0 ,
stage heights of
and SFC (below)
of the Little
3 5 ° 3 9 ' 2 5 " N ,
9 2 ° 1 7 ' 3 4 " N ;
dotted line (at
1.53 m for MFD,
and 1.02 m for
the stage height
at which drying
2008 M.S. Wine, M.R. Weston, and R.L. Johnson 673
MFD (Tukey’s: P < 0.01), and MFA and MFC had more cobble than MFD
(Tukey’s: P < 0.01).
Cobble embeddedness was low at all sites (Table 2). However, there were
significant differences among sites (F3,163 = 10.772, P < 0.001), with more
embeddedness upstream at MFA and MFB than at MFC and MFD (Tukey’s:
P < 0.05).
Fishes of headwater streams, including Yellowcheek Darters, have
evolved in systems subject to periodic drying. Recolonization of previously
dried and extirpated sites must therefore be a common feature of their life
histories. Within the headwaters of the Little Red River, low water conditions
during the late 1990s resulted in habitat loss in a system that had
previously lost extensive portions of downstream habitat due to reservoir
impoundment. When upstream sites of the Little Red River drainage system
Table 3. Arithmetic means and standard error of the mean (second line) of physical variables
measured for riffl e sites for the Little Red River, AR. All measurements were taken during low
fl ow, Spring 2001 to Fall 2003. Discharge, velocity, and depth are therefore not representative
of high-fl ow conditions.
Discharge Velocity Depth Substrate %
Site (m3/s) (m/s) (m) Sand Gravel Cobble Embededness
A 0.33 0.69 0.14 10.60 58.80 31.30 13.20
(0.05) (0.05) (0.01) (1.51) (4.67) (5.62) (2.91)
B 0.11 0.18 0.06 5.30 25.90 60.90 11.20
(0.11) (0.27) (0.04) (1.45) (3.08) (4.08) (1.48)
C 0.73 0.80 0.18 6.10 58.40 31.80 2.40
(0.19) (0.04) (0.01) (1.31) (3.89) (3.82) (0.66)
D 0.66 0.88 0.21 19.70 57.20 18.50 7.40
(0.12) (0.04) (0.02) (1.89) (3.40) (2.61) (1.03)
A 0.44 0.82 0.13 5.40 37.0 54.0 6.30
(0.07) (0.07) (0.01) (1.29) (5.66) (5.74) (1.48)
B 0.37 0.63 0.16 N/A N/A N/A N/A
(N/A) (N/A) (N/A)
C 0.40 0.99 0.22 11.80 56.40 31.80 12.80
(0.05) (0.09) (0.02) (2.45) (4.01) (4.50) (2.17)
A 0.31 0.64 0.15 N/A N/A N/A N/A
N/A N/A N/A
B 0.47 0.77 0.17 N/A N/A N/A N/A
(0.09) (0.15) (0.01)
Turkey Fork 0.45 0.78 0.15 N/A N/A N/A N/A
(0.07) (<0.01) (<0.01)
Beech Fork 1.01 0.59 0.14 N/A N/A N/A N/A
(0.13) (0.04) (<0.01)
674 Southeastern Naturalist Vol. 7, No. 4
dry, there are few downstream riffl es to serve as refugia for maintaining
populations. For example, Wine (2004) calculated a reduction of available
Yellowcheek Darter habitat due to drought in 1999–2000 ranging from 30%
for the Middle Fork up to 70% for the South Fork.
As riffl es dewater, occupants of the riffl e must move into neighboring
pools or, as appears to occur for Yellowcheek Darters, move large distances
downstream to a persistent riffl e or perish. Conversely, the sympatric Rainbow
Darter and Campostoma anomalum Rafinesque (Central Stoneroller)
were frequently found in pools following dewatering of upstream riffl es, and
occurred in greater frequencies in riffl es than historically (Robison and Harp
1981, Wine 2004). This apparent obligate occupation of riffl e habitats by
Yellowcheek Darters provides insight for the relatively slow recolonization
of upper sites compared to other riffl e fishes.
Numerous studies have examined downstream faunal changes following
stream impoundment (e.g., Johnson and Harp 2004, Johnson et al. 2006a,
Shaver et al. 1997). Less frequently studied are upstream faunal effects
from impoundment (Erman 1973, Herbert and Gelwick 2003, Winston et al.
1991). Stream impoundment has been associated with the decline of other
darter species including the threatened E. nianguae Gilbert and Meek (Niangua
Darter; Mattingly and Galat 2002) and endangered E. doration Jordan
and Brayton (Bluemask Darter; Layman et al. 1993).
Several monthly stage-height averages during 1999–2000 (September
and October of both years; USGS 2006) were below that required to maintain
surface fl ow in the upper stream sites. As these are monthly averages,
they refl ect prolonged periods of riffl e drying. Daily stage height fl uctuations
below these monthly averages would represent more extensive dewatering.
Water levels during 1999 and 2000 represent 25-year lows (USGS 2006).
Fish often recolonize stream reaches rapidly after disturbance events
such as drought, provided there are no barriers to their movement (Peterson
and Bayley 1993). Distances between suitable habitats can affect the success
of dispersal and recruitment (Lonzarich et al. 1998). For example, drying
of riffl es during 1999–2000 (and previously during 1998 [Mitchell 1999])
occurred for several km downstream of our upstream study sites, yet intermittent
pools remained. This extent represents long distances for upstream
recolonization to occur. Data are inconsistent as to the potential for darter
migration patterns among species. Some darter species exhibit high site fidelity
(e.g., E. radiosum Hubbs and Black [Orangebelly Darter; Scalet 1973],
E. cragini Gilbert [Arkansas Darter; Labbe and Fausch 2000]), whereas
other species are highly mobile (14 species studied by Winn ). During
normal fl ow conditions, Yellowcheek Darters demonstrate high site fidelity
(Weston and Johnson 2008). However, migration patterns as these streams
dewater remain to be studied. A key niche difference identified among darter
species was that the species studied by Winn (1958) were eurytypic and had
widespread geographic distribution, whereas darter species in Scalet (1973)
2008 M.S. Wine, M.R. Weston, and R.L. Johnson 675
and this study were obligate riffl e species and endemic to small watersheds.
Site fidelity may contribute to limited distribution of some darter species,
whereas the ability or propensity to travel may contribute to the widespread
geographic distributions of other darter species.
The decline of Yellowcheek Darters during 1999–2001 was pervasive
throughout the Little Red River drainage system. Comparisons to the Robison
and Harp (1981) survey and more recent sampling in 2003–2004
show consistently low densities for comparable sites, other than for site
SFC. With the rewatering of riffles since 2000, subpopulations within the
upper South Fork have apparently re-established. In contrast, upper sites
in the Middle Fork have not effectively recolonized, particularly site MFA.
The Middle Fork has a greater stream gradient than the South Fork; therefore,
flow and biological responses to that flow should be more variable
in the Middle Fork. Archey Fork sites were almost extirpated, with only
23 individuals observed sporadically in the lower site during seven site
visits; more recent visits indicate that this site has since been repopulated
(M.S. Wine, pers. observ.). Unlike the Turkey Fork, which drains directly
to Greers Ferry Reservoir, Archey Fork merges with the South Fork prior
to entering the reservoir. Downstream South Fork populations may have
assisted in the repopulating of Archey Fork sites. Conversely, the extirpation
of the Turkey Fork population has continued through the present (M.S.
Wine, pers. observ.). McDaniel (1984) noted a high amount of large cobble
and boulders (80%) in the Turkey Fork and recognized that much of the
stream at that time represented suboptimal Yellowcheek Darter habitat.
Similar results have been identified for other riffle species (e.g., Noturus
nocturnus Jordan and Gilbert [Dusky Darter]; Herbert and Gelwick 2003)
occupying previously connected streams upstream of reservoirs. Turkey
Fork has the smallest watershed of the study streams, and prolonged and
frequent drying of this stream could explain localized species extinctions.
This population represents a critical loss of genetic diversity for Yellowcheek
Darters (Mitchell et al. 2002).
Yellowcheek Darter densities of colonized sites presently range from
0.18–1.23 adults/m2, and are comparable to historic levels (Robison and
Harp 1981). Trends in the data indicate that Yellowcheek Darter densities are
probably closely linked to water levels. Increases in both fl ow and densities
occurred with the more recent sampling period. Flow ceased at upstream
sites when water levels fell below 1.53 m and 1.02 m at MFD and SFC,
respectively. The loss of downstream refugia as a result of the construction
of Greers Ferry Dam in 1964 may exacerbate natural climatic cycles, which
include drought, resulting in stream-wide extirpations.
Financial support was provided by the US Fish and Wildlife Service. We thank G.
Harp, S. Blumenshine, R. Nilius, S. Rogers, S. Shoults, and B. Wagner for technical
676 Southeastern Naturalist Vol. 7, No. 4
support, and R. Mitchell, T. Harmon, S. Fowler, L. Hodgens, J. Gore, N. Bickford,
J. Fullington, K. Gillespie, B. Intres, M. Johnson, A. Peck, T. Sanders, M. Trevino,
C. Dawes, and C. Weston for assistance with collection. We also thank G. Harp, C.
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