Population Structure, Status, and Conservation of Two Graptemys Species from the Pearl River, Mississippi Author(s): Will Selman and Robert L. Jones Source: Journal of Herpetology, 51(1):27-36. Published By: The Society for the Study of Amphibians and Reptiles DOI: http://dx.doi.org/10.1670/15-082 URL: http://www.bioone.org/doi/full/10.1670/15-082 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Journal of Herpetology, Vol. 51, No. 1, 27–36, 2017 Copyright 2017 Society for the Study of Amphibians and Reptiles Population Structure, Status, and Conservation of Two Graptemys Species from the Pearl River, Mississippi 1,2,3 4 WILL SELMAN AND ROBERT L. JONES 1 Department of Biological Sciences, University of Southern Mississippi, 118 College Drive, 5018, Hattiesburg, Mississippi, USA 2 Department of Biology, Millsaps College, 1701 North State Street, Jackson, Mississippi, USA 4Mississippi Department of Wildlife, Fisheries, and Parks, Museum of Natural Science, 2148 Riverside Drive, Jackson, Mississippi, USA ABSTRACT.—Graptemys is one of the least studied turtle genera in North America. Graptemys oculifera (Ringed Sawback) and Graptemys pearlensis (Pearl Map Turtle) are endemic to the Pearl River system of Mississippi and southeastern Louisiana. We studied both species near Columbia, Mississippi, on the Pearl River via a trapping and basking surveys over two years. Additionally, five sites including Columbia were trapped for 27 years to determine long-term trends in capture success and relative abundance (RA). At the Columbia site, body size distribution was bimodal for G. oculifera and atypically unimodal for G. pearlensis; G. pearlensis body lengths were smaller than museum specimens. Population estimates for G. oculifera at the Columbia site indicate a stable population over 25 years. Long-term RA trends indicated that G. pearlensis was less common than G. oculifera in all periods and at all sites from 1988 to 2013. Trends in long-term capture success for G. oculifera and G. pearlensis were negative at all sites, with significant declines at three sites for both G. oculifera and G. pearlensis. Declines occurred both upstream and downstream of a major reservoir. Therefore, a combination of factors (including altered hydrology, human disturbance, lack of recruitment, excessive sedimentation, impaired water quality, and/or the pet trade) appear to be contributing to declines. Additional conservation and protection is warranted for G. pearlensis, and current protections for G. oculifera should be extended. Future studies should continue at our long-term sites to determine whether population declines persist or whether populations stabilize. Understanding wildlife population sizes and demography are either G. pulchra (sensu lato; Lovich and McCoy, 1992) or G. central tenets for species conservation efforts; however, these gibbonsi (sensu lato; Ennen et al., 2010); 2) it was perceived to data are lacking for many southeastern freshwater turtle species need less conservation attention, because it was not a drainage to aid in conservation efforts. In particular, Graptemys (map endemic as either G. pulchra (sensu lato) or G. gibbonsi (sensu turtles and sawbacks) is considered one of the least studied lato); and 3) it was overshadowed by the federally threatened turtle genera in North America (Lovich and Ennen, 2013); yet status of G. oculifera. The latter directed more funding resources many species within the genus are of conservation concern toward G. oculifera research to understand basic life-history and (Buhlmann and Gibbons, 1997; van Dijk et al., 2014) and lack ecological characteristics, with data for G. pearlensis only basic life-history information (Lindeman, 2013). Further, most of collected secondarily. the species solely inhabit riverine environments and associated The first objective in this study was to document in-depth water bodies (e.g., oxbows and bayous), with nine of the 14 population structure and densities of both G. oculifera and G. species endemic to single river drainages of the Gulf of Mexico pearlensis at one site on the lower Pearl River of southern (Lindeman, 2013). Many of the endemic Gulf Coast Graptemys Mississippi. The second objective was to examine trends in are considered the least understood within the group (Lovich trapping success (i.e., catch per unit effort, CPUE) and relative and Ennen, 2013). abundance (RA) at five sites throughout the Pearl River system Two such species, Graptemys oculifera (Ringed Sawback; Baur, in Mississippi for 27 yr. The third goal was to compare the data 1890) and Graptemys pearlensis (Pearl Map Turtle; Ennen et al., collected in this study to historical data for both species within 2010), occur sympatrically in the Pearl River system of central the drainage. Mississippi and southeastern Louisiana. Considerable knowl- edge is available for G. oculifera including population densities (Jones and Hartfield, 1995; Dickerson and Reine, 1996; Linde- MATERIALS AND METHODS man, 1998; Shively, 1999), population structure (Jones and Hartfield, 1995), reproductive ecology (Jones, 2006), and Study Sites.—For the detailed demographic study, we conduct- population genetics (Gaillard et al., 2015). Most of this ed fieldwork on 8.3 river kilometers (rkm) of the Pearl River near information was made possible because the species was listed the town of Columbia (Marion County, MS; Fig. 1). The as federally threatened in 1986 (USFWS, 1986) and with the Columbia site is characteristic of a medium-sized (~75–175 m undertaking of proposed studies outlined in the G. oculifera wide), Gulf Coastal Plain river, with alternating pointbar and recovery plan (Stewart, 1988). Most of the available data for G. cutbank sections, abundant submergent and emergent dead- pearlensis, however, is coincidental to visual population density wood snags, and a sand and gravel substrate. The flow of the 3 surveys focused on G. oculifera (Dickerson and Reine, 1996; Pearl River (discharge: 24–1700 m /sec) is primarily regulated by Lindeman, 1998; Shively, 1999), with all data reported prior to the Ross Barnett Reservoir spillway, ~240 rkm upstream from the its recognition as a separate Graptemys taxon (Ennen et al., 2010). site. The site is surrounded by riparian bottomland forest (i.e., Presumably, the lack of data available for G. pearlensis is because Water Oak [Quercus nigra], Baldcypress [Taxodium distichum], 1) it previously had a much wider range when considered as Sycamore [Platanus occidentalis], Spruce Pine [Pinus glabra]), as well as a small amount of pasture land and a small number of 3Corresponding author. E-mail: [email protected] fishing camps. The eastern bank at the southern end of the site is DOI: 10.1670/15-082 bordered by a local park, which is a county-maintained and - 28 W. SELMAN AND R. L. JONES FIG. 1. The geographic location of the Pearl River in the southeastern United States (top inset) and map of sample sites in central Mississippi (bottom). Cross-hatching represents areas where Graptemys oculifera and Graptemys pearlensis co-occur, whereas stippling represents upstream areas only occupied by G. pearlensis (based on maps by Lindeman, 2013) and new records of Lindeman (2014a, b). operated park with a boat launch, ball fields, and pavilions. (Lakeland, Monticello, Columbia). These study sites are Boating levels on the river are relatively low even though the described in more detail by Jones and Hartfield (1995). boat ramp provides river access. Short-Term Study.—During 2005–2006, Graptemys species were For the long-term study (1988 and 2014), we trapped over trapped at the Columbia site for 2–4 days per month from April to October. We trapped turtles by attaching open topped basking multiple sampling periods, not including the 2005/2006 traps (made of 3/4-inch PVC coated crawfish wire; Fish Net trapping at Columbia described below. This includes at the Company, Jonesville, LA) to emergent deadwood and left them Columbia site (N = 6 sampling periods) and four other sites— slightly submerged (Selman et al., 2012). Traps varied in size Carthage (6), Ratliff Ferry (7), Lakeland (7), and Monticello (7)— (from 56 · 46 · 31 cm to 122 · 61 · 25 cm) and were attached to determine long-term trends in species CPUE and RA (Fig. 1). with nails and cotton twine to known Graptemys basking logs or Two sites are located upstream of the Ross Barnett Reservoir branches used by both sexes and different size classes. Trap sites (Carthage, Ratliff Ferry), and three sites are located downstream were later approached rapidly via motorized boat, which startled PEARL RIVER GRAPTEMYS STATUS AND CONSERVATION 29 basking turtles into the traps. A maximum of 17 traps were used 1996), because it did not require uniquely marked turtles, and during a trap-day, and each trap was checked approximately additional marked individuals could be added to the popula- every hour; traps were occasionally adjusted because of tion between survey intervals. fluctuating water levels or moved if turtles avoided the trap site. For the long-term study, we used a linear regression to Turtles also were captured opportunistically by hand or by dip analyze the RA of G. pearlensis for all sites over the 27-yr time net. period; G. oculifera RA trend would be the inverse relationship.