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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. 4 714 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 - Manuscript Editor: Arthur Bogan Southeastern Naturalist 715 J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 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 Southeastern Naturalist J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 2015 Vol. 14, No. 4 716 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. Southeastern Naturalist 717 J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 2015 Vol. 14, No. 4 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 Southeastern Naturalist J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 2015 Vol. 14, No. 4 718 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 Southeastern Naturalist 719 J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 2015 Vol. 14, No. 4 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. Literature Cited Academy of Natural Sciences Philadelphia (ANSP). 2014. Malacology Collection. Available online at Accessed 15 September 2014. Florida Department of Environmental Regulation (FDER). 1987. An investigation of the water quality of the Ochlockonee River. Tallahassee, FL. 287 pp. Harvard University Museum of Comparative Zoology (MCZ). 2014. Malacology Collection. Available online at Accessed 15 September 2014. Hemming, J.M., P. Winger, W. Gierhart, R. Jarvis, H. Blalock-Herod, and J. Ziewitz. 2005. Water and sediment quality survey of threatened and endangered freshwater mussel habitat in the Ochlockonee River Basin. 71 pp. North Carolina Museum of Natural History (NCSM). 2015. Invertebrate database.Available online at Accessed September 15, 2014. Poff, L.N., J.D. Allen, M.B. Bain, J.R. Karr, K.L. Prestgaard, B.D. Richter, R.E. Sparks, and J.C. Stromberg. 1997. The natural flow regime. Bioscience 47:769–784. Southeastern Naturalist J. Holcomb, M. Rowe, J. Williams, and S. Pursifull 2015 Vol. 14, No. 4 720 Stewart, P.M., S. Bhattarai, M.W. Mullen, C.K. Metcalf, and E.G. Reategui-Zirena. 2012. Characterization of large wood and its relationship to pool formation and macroinvertebrate metrics in southeastern coastal plain streams, USA. Journal of Freshwater Ecology 27(3):351–365. University of Florida Museum of Natural History (UF). 2014. University of Florida Invertebrate Zoology Main Collection. Available online at dbs/malacol_pub. asp. Accessed 15September 2014. University of Michigan Museum of Zoology (UMMZ). 2014. Mollusk Collection. Available online at Accessed 15 September 2014. US Fish and Wildlife Service (USFWS). 1998. Endangered and threatened wildlife and plants; determination of endangered status for five freshwater mussels and threatened status for two freshwater mussels from eastern Gulf slope drainages of Alabama, Florida, and Georgia. Federal Register 63(50):12664–12687. USFWS. 2007. Endangered and threatened wildlife and plants; designation of critical habitat for five endangered and two threatened mussels in four northeast Gulf of Mexico drainages. Federal Register 72(220):64286–64340. Williams, J.D., R.S. Butler, G.L. Warren, and N.A. Johnson. 2014. Freshwater Mussels of Florida. University of Alabama Press, Tuscaloosa AL. 498 pp.