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2009 SOUTHEASTERN NATURALIST 8(2):245–254
Seven Populations of the Southern Kidneyshell
(Ptychobranchus jonesi) Discovered in the
Choctawhatchee River Basin, Alabama
Michael M. Gangloff1,* and Paul W. Hartfield2
Abstract - Ptychobranchus jonesi (Southern Kidneyshell) is one of the most
imperiled freshwater mussels in North America. It is endemic to eastern Gulf of
Mexico drainages from the Escambia to the Choctawhatchee River basins. Numerous
recent surveys considered it restricted to a single population in the West Fork
Choctawhatchee River in southeastern Alabama. We conducted comprehensive
(9–15 hr per site) mussel searches in three high-quality reaches of the Pea River, a
Choctawhatchee River tributary, to assess microhabitat associations for the Southern
Kidneyshell. Habitat features were later used to identify subsequent search localities.
We found undetected Southern Kidneyshell populations at a total of seven localities
in the Choctawhatchee River Basin, AL. Although widely-distributed, the Southern
Kidneyshell is extremely rare (n = 13) and comprised <0.3% of all mussels encountered.
Prior surveys may have underestimated the distribution of the Southern
Kidneyshell because they were broadly focused and thus did not expend the necessary
effort to detect this rare mussel. Targeted searches in preferred microhabitats
greatly increased Southern Kidneyshell catch rates and were used to detect four of
the seven new populations. These results suggest that extensive searches within highquality
habitats are critical to detecting rare mussels in patchy habitats.
Ptychobranchus jonesi van der Schalie (Southern Kidneyshell) is one of
the most imperiled freshwater mussels in North America (Blalock-Herod et
al. 2005). Historically, it was found throughout the Choctawhatchee River
Basin (CRB) and sporadically in the Escambia and Yellow river basins of
south Alabama and northwest Florida, but in the decade prior to this survey
was believed to persist at only one reach of the West Fork Choctawhatchee
River in southeastern Alabama (Blalock-Herod et al. 2005, Clench and
Turner 1956, Pilarczyk et al. 2006, Williams et al. 2008). The Southern Kidneyshell
was also collected as recently as 1993 from the Pea River near the
AL Highway 267 bridge in Coffee County, AL. However, subsequent surveys
did not detect it at that locality, and most recent authors considered the
West Fork Choctawhatchee to be the sole remaining population (Blalock-
Herod et al. 2005, Pilarczyk et al. 2006).
The Southern Kidneyshell was first described from specimens collected
in the Pea River near Preston’s Mill in Dale County, AL (Blalock-Herod
et al. 2005, van der Schalie 1934). It was recently elevated by the US
1Appalachian State University, Biology Department, 572 Rivers Street, Boone, NC
28608. 2US Fish and Wildlife Service, Jackson ES-Field Office, 6578 Dogwood View
Parkway, Jackson, MS 39213. *Corresponding author - firstname.lastname@example.org.
246 Southeastern Naturalist Vol. 8, No. 2
Fish and Wildlife Service (USFWS) to candidate species status (USFWS
2004) and is considered a G1 (critically imperiled) species by NatureServe
(www.natureserve.org). The State of Alabama considers Southern Kidneyshell
a species of highest conservation concern (Garner et al. 2004).
Pilarczyk et al. (2006) conducted the most recent (2003 and 2004) mussel
surveys in the CRB and reported Southern Kidneyshell from a short reach
of the upper West Fork Choctawhatchee River in Barbour County, AL. It
was also recently reported alive in the Pea River in Dale County, AL in the
early 1990s (Blalock-Herod et al. 2005; Williams et al. 2008). Southern
Kidneyshell may be extirpated from the Escambia and Yellow river basins;
it has not been reported from these drainages since the 1930s (Butler 1989,
Garner et al. 2004; Pilarczyk et al. 2006; Williams and Butler 1994; Williams
et al. 2008). Additionally, historical records in the Florida Museum of Natural
History exist for the lower Choctawhatchee River in Florida and at least one
Pea River tributary (Flat Creek) in Alabama (Blalock-Herod et al. 2005).
Comprehensive searches used 9–15 hours of search effort per site at three
stations (Stations 1–3) in the Pea River during fall 2006 and summer 2007.
At the downstream comprehensive site (Station 1), we surveyed a 1500-m
section of the Pea River near Samson in Geneva County, AL. This section
of the Pea is deeper and wider (Station 1 mean depth = 0.8 m, max depth =
3.1 m, mean width = 32 m) compared to the upstream comprehensive sites
(Station 2 mean depth = 0.3 m, max depth = 0.8 m, mean width = 21 m;
Station 3 mean depth = 0.6 m, max 1.8 m, mean width = 19.3 m). We used
mask and snorkel and SCUBA equally at Station 1, and survey effort was
standardized to 1 person-hour per 100 m of stream.
Upper Pea River comprehensive Stations 2 and 3 are located in Coffee
County, AL. Station 2 comprises a 150-m reach beginning ≈300 m downstream
of the Coffee County Road 107 bridge and Station 3 is comprised
of two 150-m reaches extending from 0–150 and 500–650 m downsteam
of Shellgrove Mill, Coffee County, AL. At Stations 2 and 3, timed searches
and 0.25-m2 quadrat transects were both utilized at 10-m intervals. We
kept careful track of search effort within each 10-m segment and then excavated
quadrats placed at 5 equi-distant intervals across the channel. We
excavated 75 quadrats at Station 2 and 150 at Station 3. Quadrats were excavated
to a depth of ≈10 cm, and all the material was passed through a 6.1-mm
sieve. This sieve size is effective at retaining unionids >8.5 mm total length
and allows for large numbers of quadrats to be searched more efficiently
(M.M. Gangloff, unpubl. data).
Targeted surveys were used to examine portions of the Pea and
Choctawhatchee rivers and their tributaries in November 2007. We examined
21 sites in reaches historically known to support the Southern Kidneyshell
2009 M.M. Gangloff and P.W. Hartfield 247
(Table 1, Fig. 1). Targeted searches were conducted in habitats adjacent to
geomorphically stable bedrock outcroppings with coarse, stable bed material.
Targeted search times ranged from 0.5–3.0 person hours per site.
Figure 1. Map of the Choctawhatchee River Basin in southeast Alabama and northwest
Florida showing the location of the two most recently known populations of the
Southern Kidneyshell in the West Fork Choctawhatchee River (gray filled star) and
the Pea River (open star, Station 8) and sites where mussel surveys were conducted
in 2006 and 2007 (open circles and triangles). Locations of seven newly discovered
Southern Kidneyshell populations are indicated by triangles. Site numbers correspond
to numbers in Table 1. Inset map shows area of detail, southeastern USA.
248 Southeastern Naturalist Vol. 8, No. 2
Table 1. Station numbers, localities, and survey dates for Ptychobranchus jonesi survey sites in the Choctawhatchee River Basin during 2006 and 2007. Text
abbreviations in the table are as follows: btwn. = between, Co. = County, CR = County Road, Hwy. = Highway.
Station Locality (latitude, longitude) Survey date
1 AL: Geneva Co., Pea River near: Geneva CR17, SW Samson (31.0648°, -86.0985°) 1 October 2006
2 AL: Coffee Co., Pea River near: Coffee CR 107 (31.5493°, -85.8308°) 21 August 2007
3 AL: Coffee Co., Pea River near: former site of Shellgrove Mill and Coffee CR 147 (31.5214°, -85.8685°) 28 June and 21 August 2007
4 AL: Coffee Co., Pea River near: AL Hwy. 134, E Alberton (31.2742°, -86.1152°) 5 and 7 November 2007
5 AL: Coffee Co., Pea River near: Coffee CR 148/151 (31.4331°, -85.9698°) 5 November 2007
6 AL: Geneva Co., Pea River near: AL Hwy. 87, N Royals Crossroads, FL (30.9974°, -85.9983°) 6 November 2007
7 AL: Geneva Co., Pea River near: boat ramp upstream AL Hwy. 52, W Samson (31.1141°, -86.0974°) 6 November 2007
8 AL: Dale Co., Pea River near: AL Hwy 167, SE Mixons Crossroads (31.4736°, -85.9028°) 7 November 2007
9 AL: Geneva Co., Pea River near: Geneva CR 474, NE Kinston (31.2315°, -86.1402°) 8 November 2007
10 AL: Dale/Houston Co., Choctawhatchee River near: AL Hwy. 92, E Clayhatchee, 2 sites ~500 m apart 10 November 2007
(31.2390°, -85.6782° and 31.2496°, -85.6712°)
11 AL: Dale Co., Choctawhatchee River btwn. AL Hwy. 123 and AL Hwy. 92 (31.3138°, -85.6493) 11 November 2007
12 AL: Dale Co., Choctawhatchee River near: US Hwy. 84, SE Daleville (31.2747°, -85.6787°) 12 November 2007
13 AL: Dale/Houston Co., Little Choctawhatchee River near: Houston CR 71 (31.2726°, -85.6474°) 12 November 2007
14 AL: Dale/Houston Co., Little Choctawhatchee River near: Houston CR 9 (31.2630°, -85.5661°) 12 November 2007
15 AL: Dale Co., West Fork Choctawhatchee River near: Dale CR 20 (31.3730°, -85.5449°) 12 November 2007
16 AL: Dale Co., East Fork Choctawhatchee River near: Dale CR 59 (31.3739°, -85.5226°) 13 November 2007
17 AL: Dale Co., West Fork Choctawhatchee River near: AL Hwy. 27 (31.4072°, -85.5325°) 12 November 2007
18 AL: Dale Co., Choctawhatchee River near: AL Hwy. 134/123 (31.2499°, -85.6712°) 13 November 2007
19 AL: Dale Co., Judy Creek near: Dale CR 20 (31.4443°, -85.5651°) 13 November 2007
20 AL: Dale Co., West Fork Choctawhatchee River near: Dale CR 36 (31.4755°, -85.5299°) 13 November 2007
21 AL: Dale Co., West Fork Choctawhatchee River near: AL Hwy. 105, NE Ozark (31.5711°, -85.4960°) 13 November 2007
2009 M.M. Gangloff and P.W. Hartfield 249
We found two Southern Kidneyshells alive in the Pea River near the
Geneva County Road (CR) 17 crossing during comprehensive sampling on
1 October 2006 (Station 1; Table 1, Fig. 1). A total of 2046 other living mussels
was found at that station during 15 person-hours within a 1.5-km study
reach (Table 1). One Southern Kidneyshell was found ≈800 m downstream
of the bridge crossing at a depth of ≈1.6 m, and the second was located
≈100 m upstream of the bridge at a depth of ≈0.4 m.
In June 2007, we found Southern Kidneyshell alive or as fresh-dead
shells at both upstream comprehensive sampling sites (Stations 2 and 3) in
the upper Pea River. Qualitative surveys at Station 2 found 226 mussels (11
spp.) alive in nine person-hours and a single fresh-dead Southern Kidneyshell
shell (Table 2). Quantitative surveys detected another 20 mussels from
seventy-five 0.25-m2 quadrats (total area = 18.75 m2) at Station 2 (density =
1.07 mussels/m2). At Station 3, mussel densities were much lower (11 mussels
total, catch per unit effort [CPUE] = 1.05 mussels/hr, quadrat density =
0.007 mussels/m2, n = 150). However, searches found one Southern Kidneyshell
alive near the downstream end of the study reach, ≈600 m downstream
of Shellgrove Mill.
The Southern Kidneyshell was very rare (n alive = 13) and comprised
0.27% of the overall mussel assemblage. However, Southern Kidneyshell
was found alive or as fresh-dead shells at eight stations, seven of which represent
significant expansions of its current range. Other candidate species
(Fusconaia burkei [Tapered Pigtoe], Hamiota australis [Southern Sandshell],
Pleurobema strodeanum [Fuzzy Pigtoe], and Villosa choctawensis [Choctaw
Bean]) were similarly rare and comprised ≈0.1–1.4% of the total mussel assemblage
(Table 2). Uniomerus tetralasmus (Pondhorn) and Toxolasma sp. cf.
parvus (Gulf Lilliput) were the least abundant taxa found during this survey
and together comprised 0.06% of the total mussel assemblage (Table 2).
We used substrate criteria (i.e., geomorphically stable bedrock outcroppings)
developed from comprehensively searched sites to target similar
habitats and found Southern Kidneyshell populations at five additional localities
in the CRB. Populations were detected at two localities in the Pea River
downstream of Elba Dam (Stations 7 and 9) and at two localities upstream of
Elba Dam (Stations 5 and 8; Table 2, Fig. 1). Although timed searches were
not conducted near Coffee CR 248 (Station 5), a fresh-dead shell was found
during qualitative investigation of the site. A lower Choctawhatchee River
population was also detected just downstream of the US Hwy 84 bridge (Station
12; Table 2, Fig. 1).
Results of this survey strongly suggest that more careful examination
of habitats in the CRB are needed to discover additional populations of
250 Southeastern Naturalist Vol. 8, No. 2
Table 2. Mussel abundance (n) and timed search mussel encounter rate (CPUE = catch per unit effort and TPUE = taxa per unit effort) at stations in the Choctawhatchee
River Basin subject to comprehensive or targeted mussel searches in 2006 and 2007. Station localities are described in Table 1 and correspond to
locations indicated by Fig. 1. No mussels were found alive at stations 11 and 13, but a fresh-dead Southern Kidneyshell shell was found at station 11; surveys at
stations 5, 15, 16, 17, and 19 did not involve mask and snorkel or view-bucket searches and are not included.
Taxon n 1 2 3 4 6 7 8 9 10 12 14 18 20 21
Elliptio arctata (Conrad) 6 5 1
(Delicate Spike) (0.11) (0.5) (0.1)
Elliptio mcmichaeli Clench & 4194 1891 25 575 66 1349 18 31 43 86 110
Turner (Fluted Elephantear) (79.9) (126) (16.7) (192) (24.7) (578) (7.2) (62) (43) (86) (110)
Elliptio pullata (Lea) 26 2 20 2 1 1
(Gulf Spike) (0.5) (0.1) (2.1) (1.3) (2.0) (1.0)
Fusconaia burkei (Walker) 4 4
(Tapered Pigtoe) (0.07) (0.4)
Hamiota australis (Conrad) 61 36 5 11 6 2 1
(Southern Sandshell) (1.16) (3.8) (0.5) (7.3) (2.4) (4.0) (1.0)
Lampsilis straminea (Lea) 159 100 14 13 11 6 7 5 3
(Southern Fatmucket) (3.03) (6.7) (1.5) (8.7) (4.1) (4.0) (3.0) (2.0) (6.0)
Lampsilis fl oridensis (Lea) 65 42 4 2 5 5 4 3
(Florida Sandshell) (1.23) (2.8) (2.7) (0.7) (1.9) (2.1) (1.6) (6.0)
Pleurobema strodeanum 72 58 1 5 3 5
(Wright) (Fuzzy Pigtoe) (1.37) (6.1) (0.1) (3.3) (1.3) (2.0)
2009 M.M. Gangloff and P.W. Hartfield 251
Table 2, continued.
Taxon n 1 2 3 4 6 7 8 9 10 12 14 18 20 21
Ptychobranchus jonesi 13 2 FD 1 5 4 1 FD
(van der Schalie) (0.25) (0.1) (0.1) (1.9) (2.7) (0.4)
Quadrula succissa (Lea) 21 2 1 4 1 2 4 7
(Purple Pigtoe) (0.4) (0.1) (0.1) (1.5) (0.7) (0.9) (1.6) (7.0)
Toxolasma sp. cf. parvus 2 2
Uniomerus tetralasmus (Say) 1 1
(Pondhorn) (0.02) (0.1)
Villosa choctawensis Athearn 7 3 1 2 1
(Choctaw Bean) (0.13) (0.2) (0.7) (0.9) (0.4)
Villosa lienosa (Conrad) 130 6 62 2 1 1 1 2 1 23 21 8 1 1
(Little Spectacle Case) (2.48) (0.4) (6.5) (0.2) (0.7) (0.3) (0.4) (1.3) (0.4) (9.2) (42) (8.0) (1.0) (1.0)
Villosa vibex (Conrad) 25 24 1
(Southern Rainbow) (0.48) (2.5) (0.1)
Search time (hr) 52.5 15 9 10.5 1.5 3 2.67 1.5 2.33 2.5 0.5 1 1 1 1
Total taxa (TPUE) 15 8 12 6 5 3 6 7 8 8 7 1 2 2 4
(0.29) (0.5) (1.3) (0.6) (3.3) (1.0) (2.3) (4.7) (3.4) (3.2) (14) (2.0) (2.0) (2.0) (4.0)
Total mussels (CPUE) 4786 2048 226 11 44 578 92 31 1370 66 61 8 44 87 119
(91.2) (137) (25.1) (1.05) (29.3) (193) (34.5) (21.3) (588) (26.4) (122) (8.0) (44) (87) (119)
252 Southeastern Naturalist Vol. 8, No. 2
the Southern Kidneyshell and other rare mussel taxa. Intensive, timed
search data reveal that overall CPUEs for Southern Kidneyshell and two
other candidate species (Tapered Pigtoe and Choctaw Bean) were <0.25
mussels per hour. Further, species-depletion curves indicate that 8–10
hours of effort at a site are needed to accurately characterize mussel assemblages
in the CRB (M.M. Gangloff, unpubl. data). However, searches
targeting mussel habitats associated with geomorphically stable bedrock
outcroppings proved to be much more efficient at detecting the Southern
Kidneyshell at new localities.
These results have important implications for future rare-mussel surveys
in Gulf Coastal Plain streams. First, surveys targeting rare species in
large streams should focus substantial effort within high-quality habitats
to determine species’ persistence (or at least to be reasonably certain that
it has been extirpated). Second, these data indicate that some taxa may
persist at very low densities within dense mussel aggregations. Previous
surveys may have failed to detect the Southern Kidneyshell because
they were likely more broadly focused on all potential habitat types.
Additionally, the Southern Kidneyshell may have been overlooked due
to “swamping” by more abundant (e.g., Elliptio mcmichaeli [Fluted Elephantear])
or superficially similar taxa (e.g., Elliptio pullata [Gulf Spike]
and H. australis [Southern Sandshell]) . Careful examination of each individual
by malacologists familiar with this fauna is tedious but essential in
distinguishing cryptic species. Survey crews should be highly trained and
capable of working in the deep, swiftly flowing reaches inhabited by the
Southern Kidneyshell in the lower Pea and Choctawhatchee rivers. Ideally,
surveys should be conducted during all seasons (under high-clarity
conditions) because the seasonal activity patterns of Southern Kidneyshell
and many other Gulf Coastal Plain unionids remain poorly known.
Targeting preferred habitats (i.e., stable substrates closely associated
with bedrock outcroppings) appeared to increase success rates. For
example, although overall Southern Kidneyshell CPUE was 0.25 individuals/
hr, targeted searches resulted in Southern Kidneyshell encounter
rates that were an order of magnitude greater at some localities (e.g.,
Stations 7 and 8; Table 1). We observed that Southern Kidneyshell and
several other candidate mussel taxa (e.g., Southern Sandshell, Fuzzy
Pigtoe) were associated with geomorphically stable limestone outcroppings.
In large, sandy Gulf Coastal Plain streams, these geologic features
may facilitate mussel aggregation by augmenting streambed stability or
otherwise enhancing habitat quality. Although relatively few mussels
were found in direct association with limestone outcrops in the relatively
high-gradient upper Pea River, large unionid aggregations were strongly
associated with these features in the lower Pea River. Throughout our surveys
of the CRB, we frequently encountered other unionid taxa in sandy,
shifting substrates, but imperiled species were rare in these habitats.
2009 M.M. Gangloff and P.W. Hartfield 253
The mechanisms responsible for the scarcity of Southern Kidneyshell and
other candidate mussel taxa were not readily apparent from these surveys.
Much of the CRB remains forest or agricultural land, and human population
densities are low. The CRB’s extensive riparian swamps may further limit
human encroachment on mussel habitats. One possible explanation for mussel
declines in the CRB may be that, over time, excessive amounts of sand
and silt have accumulated in the mainstem Pea and Choctawhatchee rivers.
A concurrent study revealed that few historical milldams persist in CRB
tributaries, suggesting that sediments accumulated in former tributary impoundments
may now be moving downstream to the mainstem rivers (M.M.
Gangloff, unpubl. data). As a result, it is possible that the mainstem Pea and
Choctawhatchee rivers are becoming filled with fine sediments. Moreover,
recent droughts have likely exacerbated sedimentation rates because lesser
fl ows permit fine sediments to accumulate. Unfortunately, evidence for this
phenomenon remains largely anecdotal, and examination of landscape-scale
changes in channel geomorphometry and sediment migration patterns are
needed to understand how tributary-derived fines affect habitats in the mainstem
Choctawhatchee and Pea rivers.
Results of this study expand the current range of Southern Kidneyshell
in the CRB by >200 km and strongly suggest that closer scrutiny of historical
collection localities is needed to properly characterize the distributions
of candidate species. It is possible that additional Southern Kidneyshell
populations may be found by careful searches of geomorphically stable
habitats associated with limestone outcroppings in other reaches of the
Choctawhatchee, Escambia, and Yellow river basins.
We wish to thank Steven Butler, Steven Bryant, Joe Hankes, Emily Hartfield,
Tandy Loffland, Tyler Mosley, Keith Ray, Hilary Strickland, Anna Thomas, and
Kevin White for assisting with fieldwork. Bob Butler, Lynn Siefferman, and two
anonymous reviewers examined an earlier version of the manuscript and provided
helpful editorial comments. Funding for this project was provided by the USFWS
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