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Seven Populations of the Southern Kidneyshell (Ptychobranchus jonesi) Discovered in the
Choctawhatchee River Basin, Alabama
Paul A. Keddy

Southeastern Naturalist, Volume 8, Number 2 (2009): 245–254

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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. Introduction 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 - gangloffmm@appstate.edu. 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). Methods Comprehensive searches 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 searches 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 Results 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). Discussion 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. Station 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. Station 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) (Southern Kidneyshell) 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 (0.04) (0.2) 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. Acknowledgments 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 Jackson, MS and Athens, GA Ecological Services Field Offices. Literature Cited Blalock-Herod, H.N., J.J. Herod, J.D. Williams, B.N. Wilson, and S.W. McGregor. 2005. A historical and current perspective of the freshwater mussel fauna (Bivalvia: Unionidae) from the Choctawhatchee River Drainage in Alabama and Florida. Bulletin of the Alabama Museum of Natural History 24:1–24. Butler, R.S. 1989. Distributional records for freshwater mussels (Bivalvia: Unionidae) in Florida and South Alabama, with zoogeographic and taxonomic notes. Walkerana 3:239–261. Clench, W.J., and R.D. Turner. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bulletin of the Florida State Museum 1:97–237. 254 Southeastern Naturalist Vol. 8, No. 2 Garner, J.T., H.N. Blalock-Herod, A.E. Bogan, R.S. Butler, W.R. Haag, P.W. Hartfield, J.J. Herod, P.D. Johnson, S.W. McGregor, and J.D. Williams. 2004. Freshwater mussels and snails. Pp. 13–58, In R.E. Mirarchi (Ed.). Alabama Wildlife. Volume 1. A Checklist of Vertebrates and Selected Invertebrates: Aquatic Mollusks, Fishes, Amphibians, Reptiles, Birds, and Mammals. University of Alabama Press, Tuscaloosa, AL. 209 pp. Pilarczyk, M.M., P.M. Stewart, D.N. Shelton, H.N. Blalock-Herod, and J.D. Williams. 2006. Current and recent historical freshwater mussel assemblages in the Gulf Coastal Plains. Southeastern Naturalist 5:205–226. US Fish and Wildlife Service (USFWS). 2004. Endangered and threatened wildlife and plants; review of species that are candidates or proposed for listing as endangered or threatened; annual notice of findings on resubmitted petitions; annual description of progress on listing actions. Federal Register 69:24875–24904 USFWS. 2005. Species assessment and listing priority assignment form: Fusconaia rotulata, Ptychobranchus jonesi, Fusconaia escambia, Hamiota australis, Pleurobema strodeanum, Villosa choctawensis, and Quincuncina burkei. Federal Register 72:69033–69106. van der Schalie, H. 1934. Lampsilis jonesi, a new naiad from southeastern Alabama. Nautilus 47:125–127. Williams, J.D., and R.S. Butler. 1994. Class Bivalvia, freshwater bivalves. Pp. 53–128, 740–742. In A.R. Ashton (Ed.). Rare and Endangered Biota of Florida. Volume 6: Invertebrates. University Press of Florida, Gainesville, FL. 75 pp. Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater Mussels of Alabama and the Mobile Basin. University of Alabama Press, Tuscaloosa, AL. 908 pp.