Discovery of the Ochlockonee Moccasinshell, Medionidus
simpsonianus, in the lower Ochlockonee River, Florida
Jordan Holcomb, Matthew Rowe, Jim Williams, and Sandra Pursifull
Southeastern Naturalist, Volume 14, Issue 4 (2015): 714–720
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Southeastern Naturalist
J. Holcomb, M. Rowe, J. Williams, and S. Pursifull
2015 Vol. 14, No. 4
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2015 SOUTHEASTERN NATURALIST 14(4):714–720
Discovery of the Ochlockonee Moccasinshell, Medionidus
simpsonianus, in the lower Ochlockonee River, Florida
Jordan Holcomb1,*, Matthew Rowe1, Jim Williams1, and Sandra Pursifull2
Abstract - An unknown population of Medionidus simpsonianus (Ochlockonee Moccasinshell)
was discovered in the lower Ochlockonee River downstream of Jackson Bluff Dam in
2014. This discovery confirms that the species is extant, extends its known range by nearly
100 rkm, and represents only the second known collection of this species in the lower Ochlockonee
River Basin. Ochlockonee Moccasinshell is endemic to the Ochlockonee River
Basin (ORB) in Florida and Georgia. It was historically known from 9 locations in the
upper ORB upstream of Lake Talquin and from 1 record in the lower ORB downstream of
Jackson Bluff Dam. Collections of Ochlockonee Moccasinshell decrease in regularity after
1950, and the last record of a live individual was 1995. We surveyed 55 sites downstream
of Jackson Bluff Dam in a reach of river having received little effort in the last 20 years. We
employed visual/tactile searches using mask and snorkel from shore to a depth of 2.5 m and
found 22 live individuals of Ochlockonee Moccasinshell at 9 locations from 47–65 river
km (rkm) downstream of Jackson Bluff Dam. Further survey effort is needed to update the
status and range of Ochlockonee Moccasinshell and other freshwater mussel populations
of the lower ORB.
Introduction
Medionidus simpsonianus (Ochlockonee Moccasinshell) is one of 6 species of
Medionidus and is a federally endangered unionid mussel endemic to the Ochlockonee
River Basin (ORB) in Florida and Georgia (USFWS 2000). Since the 1960s,
its range has generally been reported as the Ochlockonee River Basin upstream of
Lake Talquin in Florida and Georgia (USFWS 1998, Williams et al. 2014). Historically
it was known from only 10 locations, most of which have only sporadic
reported occurrences from the 1920s to the early 1990s (Fig. 1; Academy of Natural
Sciences Philadelphia [ANSP 2014], Harvard University Museum of Comparative
Zoology [MCZ 2014], North Carolina Museum of Natural Sciences [NCSM 2015]
Florida Museum of Natural History, University of Florida [UF 2014], University of
Michigan Museum of Zoology [UMMZ 2014], the Florida Fish and Wildlife Conservation
Commission Mollusk Database [FWC, Gainesville, FL, unpubl. data],
and USFWS collections database [USFWS, Panama City, FL, unpubl. data]). The
last Ochlockonee Moccasinshell taken live was found in the Ochlockonee River
about 15 air km NW of Tallahassee, FL, in 1995 (UF 372995).
Despite considerable survey effort at historical Ochlockonee Moccasinshell
localities and many additional sites in the last 10 years, no Ochlockonee
1Florida Fish and Wildlife Conservation Commission, 7386 NW 71st St, Gainesville, FL
32653. 2US Fish and Wildlife Service, Panama City Field Office, 1601 Balboa Ave, Panama
City, FL 32405. *Corresponding author - Jordan.holcomb@myfwc.com.
Manuscript Editor: Arthur Bogan
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2015 Vol. 14, No. 4
Moccasinshell have been collected (USFWS, Panama City FL, unpubl. data). The
upper ORB (upstream of Jackson Bluff Dam) has received most of the attention
since the 1920s, with >100 localities surveyed in just the last 7 years (FWC, unpubl.
data; UF; USFWS, unpubl. data). Many of these recent surveys were specifically
conducted to find Ochlockonee Moccasinshell. Limited road access precluded early
malacologists from intensively searching sites downstream of Jackson Bluff Dam,
with the FL State Road 20 crossing receiving nearly all of the effort. However, there
is one record of Ochlockonee Moccasinshell from the “Ochlockonee River, Wakulla
Co., Florida” from 1897 (MCZ 186926). The vagueness of this locality places the
collection downstream of the current site of Jackson Bluff Dam, which was built 34
y after the collection. Few additional collections were made in the lower ORB until
the late 1980s and early 1990s when much more survey effort was expended (FWC,
unpubl. data; USFWS, unpubl. data). However, relatively little attention has been
given to the lower ORB recently, as only 13 sites have been surveyed in the last 7
years (USFWS, Panama City, FL, unpubl. data). These most recent efforts consisted
of both general mussel surveys and surveys specifically targeting Ochlockonee
Moccasinshell, but contained distributional gaps and failed to explore habitats >1
m in depth. Such information gaps limit our understanding of the mussel fauna of
the lower ORB
This study attempted to address some of these knowledge gaps regarding distribution
and habitat. For this study, our sampling efforts were aimed at filling geographic
coverage gaps left by previous surveys and conducting general freshwater mussel
distribution surveys in a variety of habitats. The data generated from these surveys
will be used to direct future long-term monitoring projects in the lower ORB.
Methods
We searched 55 sites 9–30 September 2014 and 6–9 October 2015. Surveys targeted
a variety of habitats (e.g., outside bends, sandbars, sloughs) within a 65-km
stretch of the lower Ochlockonee River where little or no survey effort had been
expended in the last 20 years (FWC, unpubl. data; USFWS, unpubl. data). Sites
were located on the Ochlockonee River from approximately 9.2 river kilometers
(rkm) upstream of the confluence of Telogia Creek, downstream to approximately
2.1 rkm downstream of Tate's Hell State Forest Womack Creek Tract boat ramp
(Fig. 1). Two to 3 searchers spent a minimum of 1 person-hour per site utilizing
mask and snorkel to conduct visual/tactile searches from the shoreline to 2.5 m
depth. Some surveys were terminated after 0.5 person-hours if few mussels (less than 10 individuals
total) were encountered or if habitat conditions were deemed unfavorable
for unionid mussels (e.g., shifting sand, highly depositional areas). All museum lots
of Ochlockonee Moccasinshell referenced in this work were personally examined
and verified by the authors (Table 2).
Results
Our survey efforts yielded 8907 mussels representing 20 species, including
22 live Ochlockonee Moccasinshell (Table 1). Ochlockonee Moccasinshell was
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observed at 9 of 55 sites surveyed and was relegated to an 18-rkm reach of the
Ochlockonee River 47–65 rkm downstream of Lake Talquin (Fig. 1). Five of the 9
sites yielded single individuals, and 1 site each yielded 2, 3, 4, and 7 specimens,
respectively (Fig. 1). These records represent the first Ochlockonee Moccasinshell
seen in 19 years, and only the second known collection of the species in the reach
of the Ochlockonee River downstream of Jackson Bluff Dam (MCZ lot # 186926).
Species assemblages at sites occupied by Ochlockonee Moccasinshell were
comprised largely of habitat generalists, and relatively few lentic-adapted taxa
(i.e., Utterbackia, Anodonta; Table 1). Additionally, our surveys indicate that as
the degree of tidal influence increases (near Mack Lake confluence; Fig. 1), the
prevalence of Ochlockonee Moccasinshell begins to decline.
Discussion
These results have implications for the conservation and management of Ochlockonee
Moccasinshell and the mussel assemblage in the lower ORB. Although
threats are relatively low in this reach of the lower river, the small population and
greatly reduced range of Ochlockonee Moccasinshell make it vulnerable to extinction.
Downstream of Jackson Bluff Dam, the river maintains much of its integrity
as it flows through mostly undeveloped lands of Apalachicola National Forest and
Figure 1. Panel A: extent of the survey reach and locations in the lower Ochlockonee River.
Panel B: entire Ochlockonee River Basin and historical Ochlockonee Moccasinshell records
in GA and FL.
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Tate’s Hell State Forest. In addition, the reservoir likely captures many of the impacts
affecting water quality and habitat above Lake Talquin (e.g., heavy sediment loads,
contaminants [FDER 1987, Hemming et al. 2005]). Although threats are relatively
low in this reach of the river, some threats associated with the dam exist and may
include unnatural flow regimes, altered water quality and temperature, and channel
incision (Poff et al. 1997). One study found DO levels were consistently low (less than 5.0
mg/L) downstream of the dam (Hemming et al. 2005). In addition, the removal of
deadhead logs may have negative effects on Ochlockonee Moccasinshell by removing
refugia and destabilizing banks and in-channel habitats important for the
lower ORB mussel fauna (Stewart et al. 2012). Thus, there should be additional examination
of life-history traits of Ochlockonee Moccasinshell. There is an especially
critical need for research of Ochlockonee Moccasinshell reproductive biology as
there have been no studies to date (Williams et al. 2014). Special management considerations
may be necessary to protect this small, remaining population.
Habitat associations reported herein for Ochlockonee Moccasinshell are
anecdotal because of time and resource constraints during our collections. All
Ochlockonee Moccasinshell were found in stable sand near flow refuges associated
with areas of increased gradient in river bends and moderately depositional habitats
(e.g., backside of a bend, downstream of a flow deflecting barrier). While some
individuals were found away from obvious stabilizing structures, logs were very
prevalent at the site containing the highest number of Ochlockonee Moccasinshell.
Table 1. All taxa encountered, total number of live mussels by species, number of sites at which each
was found, number of Medionidus simpsonianus (Ochlockonee Moccasinshell) sites each occupied,
and mean relative abundance at those sites (% abund.).
# M. s.
Total # sites %
Scientific name Common Name live sites occupied abund.
Anodonta heardi (Gordon and Hoeh) Apalachicola Floater 14 4 - -
Elliptio crassidens (Lamarck) Elephantear 4 2 1 1.18
Elliptio jayensis (Lea) Florida Spike 6269 52 9 65.43
Elliptio purpurella (Lea) Inflated Spike 2 2 1 0.31
Elliptoideus sloatianus (Lea) Purple Bankclimber 320 21 6 12.02
Glebula rotundata (Lamarck) Round Pearlshell 73 10 - -
Lampsilis floridensis (Lea) Florida Sandshell 384 45 9 4.69
Lampsilis straminea (Conrad) Southern Fatmucket 475 41 9 6.82
Medionidus simpsonianus (Walker) Ochlockonee Moccasinshell 22 9 - 1.41
Megalonias nervosa (Rafinesque) Washboard 30 15 3 1.49
Pyganodon grandis (Say) Giant Floater 14 8 1 0.93
Quadrula infucata (Conrad) Sculptured Pigtoe 203 33 9 5.07
Toxolasma parvum (Barnes) Lilliput 40 1 - -
Toxolasma paulum (Lea) Iridescent Lilliput 705 46 9 6.04
Uniomerus carolinianus (Bosc) Eastern Pondhorn 14 12 1 0.31
Utterbackia imbecillis (Say) Paper Pondshell 3 2 - -
Utterbackia peggyae (Johnson) Florida Floater 72 23 1 1.16
Villosa lienosa (Conrad) Little Spectaclecase 59 23 4 1.32
Villosa vibex (Conrad) Southern Rainbow 45 27 6 0.95
Villosa villosa (B.H. Wright) Downy Rainbow 159 31 5 0.85
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All of the individuals found at this site were immediately adjacent to 2 partially
buried logs positioned perpendicular to flow, creating a significant flow refuge,
stabilizing sediment, and providing potential host-fish habitat.
Our survey effort in the lower ORB suggests certain habitats may have been
overlooked by other recent and historical surveys and suggests the potential for
the presence of 2 other federally endangered species, Hamiota subangulata (Lea)
(Shinyrayed Pocketbook) and Pleurobema pyriforme (Lea) (Oval Pigtoe). There
is only 1 record of Shinyrayed Pocketbook (ANSP 360553) and no records of
Table 2. Table showing all Medionidus simpsonianus museum lots the authors verified with corresponding
localities and one locality from the FWC-Database not represented in museum collections.
* represents an author-approximated locality in [ ] based on the vague locality provi ded originally.
Lot # Date Location
ANSP 348841 1978-10-21 Ochlockonee River, both sides under Bridge at US Rt.27
MCZ 105141 1934-08-00 11 mi NW of Tallahassee, Ochlockonee River [at FL157]*
MCZ 186926 1897-07-00 Ochlockonce [Ochlockonee] River, Wakulla County, FL
MCZ 190298 1954-08-26 7 mi S of Cairo, Ochlockonee River [GA93, 6.5 mi SE of Cairo] *
MCZ 190299 1954-09-04 Between Reno and Beachton [at Hadley Ferry Rd], Ochlockonee R. *
MCZ 190300 1954-09-06 about 8 mi W of Tallahassee, Ochlockonee River [at US90]*
MCZ 190301 1954-09-09 3.5 mi E of Quincy, Little River [at US90]*
MCZ 288406 1934-09-24 Near Quincy, Ochlochonee [Ochlockonee] River
NCSM 6812 1977-06-24 Ochlockonee River at US 27
NCSM 62933 1957-11-15 Ochlockonee River, at Rt. 90, 8 mi. WNW of Tallahassee
OSUM 75564 1985-06-14 Ochlockonee River 11 mi NW of Tallahassee [at FL157]*
UMMZ 58676 - Ochlockonee River, 8.0 mi. W of Tallahassee [at US90]*
UMMZ 98510 - Calvary
UMMZ 206740 - Tallahassee
UMMZ 218207 1964-06-22 Ochlockonee River, at US 27
UMMZ 234736 1964-06-22 Ochlockonee River, at US 27, 11.0 mi. N Tallahassee
UMMZ 237057 1905-05-16 Ochlockonee River, near Tallahassee
UMMZ 246941 - [Ochlockonee River] 16 mi. NE [N] of Tallahassee [Grady/Leon CR12]*
UMMZ 300010 - Calvary
UF 1912 - Ochlocknee [Ochlockonee] R., 10 mi NE [NW] Tallahassee [at
FL157]*
UF 4158 1931-11-13 Ochlockonee R., 7 mi W of Tallahassee [at US90]*
UF 4162 1933-06-08 Ochlocknee [Ochlockonee] R., 7 mi W of Tallahassee [at US90]*
UF 4164 1930-06-08 Ochlockonee R., on Jacksonville-pensacola Hwy
UF 8399 1931-11-13 Ochlocknee [Ochlockonee] R., 7 mi W of Tallahassee [at US90]*
UF 8402 1920-06-08 Ochlockanee [Ochlockonee] R., on Jacksonville-Pensacola Hwy
UF 61498 1974-09-28 Circa 11 mi N of Tallahassee, at Highway 27, Ochlockonee River
UF 133937 1969-07-04 Ochlockonee River, 5.8 mi SE Havana [at US27] *
UF 135333 1987-10-09 8 km SSE of Havana, US 27 Crossing, Ochlockonee River
UF 229357 - Ochlochonee [Ochlockonee] R., 10 mi NE [NW] of Tallahassee [at
FL157]*
UF 372995 1995-09-22 Ochlockonee River at Fl Rt. 153 [FL157] Crossing~5 Air Miles NW
of Tallahassee
UF 376259 1993-08-11 Ochlockonee River at US27 Crossing, at 6.2 Air Mi. SSE of Havana.
UF 381317 1993-05-26 Ochlockonee River at Cr154 [Hadley Ferry Rd] Crossing, at 10 air mi.
S of Cairo
FWC-unpubl. 1988-10-15 Ochlockonee River at US84
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Oval Pigtoe downstream of Jackson Bluff Dam. The population of Elliptoideus
sloatianus (Purple Bankclimber) in the lower ORB appears to be stable, and that
species was the fifth most abundant mussel encountered (Table 1). Purple Bankclimber
also appears to be recruiting, evidenced by subadults less than 100 mm in length
collected at several locations. Another freshwater mussel, Alasmidonta wrightiana
Walker (Ochlockonee Arcmussel), last collected in 1931 and presumed extinct
(Williams et al. 2014), may exist in some of the more extensive backwater habitats
and sloughs in this reach of the lower ORB. Although our surveys detected
the majority of 22 native species reported from the ORB, more intensive survey
effort is needed in the lower river to better delineate the current range of Ochlockonee
Moccasinshell, as well as to sufficiently document the presence or absence
of Shinyrayed Pocketbook, Oval Pigtoe, and Ochlockonee Arcmussel.
Acknowledgments
We wish to thank the curators and collection managers of the following institutions
for their assistance in providing access to mussel collections and catalogue data: Ohio
State Museum of Biological Diversity—George Thomas Waters and Caitlyn Byrne;
North Carolina Museum of Natural Sciences—Arthur Bogan and Jamie Smith; Academy
of Natural Sciences Philadelphia—Paul Callomon; Museum of Comparative Zoology,
Harvard University—Marat Recevik, Adam Baldinger, and Richard Johnson; Florida
Museum of Natural History—Amanda Bemis, Gustav Paulay, and John Slapcinsky; and
University of Michigan Museum of Zoology—Jack Burch, Taehwan Lee, and Diarmaid
O’Foighil. Gary Warren made revisions which substantially improved earlier versions of
this manuscript. We would also like to thank Misty Penton with Florida Fish and Wildlife
Conservation Commission, for her help in procuring funding from the USFWS to
make these surveys possible.
Disclaimer: the findings and conclusions in this article are those of the authors and do
not necessarily represent the views of the US Fish and Wildlife Service.
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