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Range Extension in Styracura (= Himantura) schmardae (Caribbean Whiptail Stingray) from The Bahamas
Owen R. O’Shea, Christopher R.E. Ward, and Edward J. Brooks

Caribbean Naturalist, No. 38

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Caribbean Naturalist 1 O.R. O’Shea, C.R.E. Ward and E.J. Brooks 22001177 CARIBBEAN NATURALIST No. 3N8o:1. –388 Range Extension in Styracura (= Himantura) schmardae (Caribbean Whiptail Stingray) from The Bahamas Owen R. O’Shea1,*, Christopher R.E. Ward1 and Edward J. Brooks1 Abstract - Styracura (= Himantura) schmardae (Caribbean Whiptail Stingray) is a cryptic batoid found throughout the Caribbean, yet is poorly known from The Bahamas. Anecdotal records suggest this animal may have been distributed throughout the Exuma Cays in the Central Bahamas, but information pertaining to its distribution within The Bahamas is sparse, and therefore is not formally recognized. Here, we present a preliminary abundance assessment and basic demographic observations of this species’ current distribution throughout The Bahamas with notes on historical accounts and habitat occupation. We documented a total of 95 individuals from 32 sites during 137 hours of survey time (0.6 rays hour-1) between January 2015 and September 2016. We captured 74% (n = 70) of the rays to collect data for several on-going studies. We employed DNA barcoding to verify our identifications. Individuals represented disc-width (WD) sizes from 228 mm to 1472 mm. Observations presented here suggest that this species can potentially remain within The Bahamas for its entire life cycle, and we provide the most up-to-date assessment of range extension by this species within The Bahamian Archipelago. Given the fragmented nature of The Bahamas islands, these data validate that surveying biological diversity across multiple spatial scales is a critical step when considering best management practices in marine environments. Introduction Styracura (= Himantura) schmardae (Werner) (Caribbean Whiptail Stingray) is a large, subcircular potamotrygonid (formerly dasyatid) whose current known range encompasses the western central and southwest Atlantic from Brazil (Gadig and Gomes 2003) north to Cuba (Salvat Torres et al. 2012), including the Gulf of Campeche and the Greater and Lesser Antilles (Stehmann et al. 1978). Although there is a paucity of scientific data regarding the Caribben Whiptail Stingray, this species is reportedly caught in artisanal fisheries throughout its range as a subsistence food source that is valued for its meat, gelatine, and oil (Charvet-Almeida and de Almeida 2006). Furthermore, the Caribbean Whiptail Stingray is often caught as by-catch in shrimp-trawl and purse-seine fisheries throughout the Caribbean, most notably in Cuba (NPOA 2015). The scientific literature is currently extremely limited in providing details of almost every aspect of this species’ life history, with the exception of studies relating to parasitism by cestodes (Brooks 1977) and nematodes (Deardorff et al. 1981). The Caribbean Whiptail Stingray is currently listed as data deficient in the International Union for the Conservation of Nature (IUCN) Red List, with unknown population sizes and trends and unresolved taxonomic questions (Compagno 1999). 1Shark Research and Conservation Program, The Cape Eleuthera Institute, PO Box EL- 26029, Rock Sound, Eleuthera, The Bahamas. *Corresponding author - owenoshea@ ceibahamas.org. Manuscript Editor: Dawn Phillip Caribbean Naturalist O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 2 Figure 1. The greater Caribbean region (inset) and specific study sites, incorporating Great Exuma and southern Exuma Cays, the northern Exuma Cays, and south Eleuthera to the east. Stars indicate sites where rays were observed but not caught. This species is largely undocumented in The Bahamas, with reports of its presence largely derived from popular sources. There is currently only 1 published account of Caribbean Whiptail Stingrays from The Bahamas, which describes the capture of 2 individual rays near Great Exuma Island in July and September 1968. These 2 sightings and subsequent capture by a local naturalist were reported by Böhlke (1969) and further referenced by Smith-Vaniz and Böhlke (1991). The larger of the 2 specimens was placed in the Academy of Natural Sciences of Philadelphia collection as ANSP 103787 (Smith-Vaniz and Böhlke 1991), where it was subsequently identified as a Caribbean Whiptail Stingray. Here, we present for the first time, recent evidence of this species’ range occupation in The Bahamas with notes on habitat association, and observations of a large mixed-sex aggregation of mature individuals. Study Sites We observed rays at 32 sites in the central Bahamas across 3 broad geographic locations: Eleuthera Island, northern Exuma Cays, and southern Exuma Cays (Fig. 1). These limestone islands are situated on the Great Bahama Bank adjacent to The Exuma Sound, which is a deep-water inlet of the Atlantic Ocean. These small, Caribbean Naturalist 3 O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 low-lying islands and mangrove-fringed creek systems are exposed to the deeper Exuma Sound to the east, and the calm, shallow-bank system to the west. We chose sites based on prior knowledge and citizen-science–derived reports that we solicited from the sailing community throughout the Exuma Islands and from dive-shop owners and tour operators to compare images and descriptions of the Caribbean Whiptail Stingray. Methods We carried out surveys on foot between January 2015 and September 2016. Five to seven observers walked transects separated by~5 m and perpendicular to the shore looking for moving, resting, or buried rays on sand flats and around entrances to creeks. Typically, we discovered buried rays when we observed their thick, muscular tails protruding above the sediment layer. We also surveyed mangrove creeks in the same manner; we caught only those rays observed in water less than 2 m deep due to safety considerations based on the size some individuals. We herded rays into a seine net and transferred them into a dip net for data collection (Fig. 2A). Once captured, we took care to ensure that the barbs (located ~⅓ Figure 2. (A) Caribbean Whiptail Ray in a dip net prior to release after being caught at Hog Cay; (B) the smallest individual measuring 228 mm WD sampled from Banshee Creek, Warderick Wells; (C) the largest individual measuring 1472 mm WD sampled from Normans Cay, and (D) aggregation of H. schmardae in the southern Exuma Cays. Caribbean Naturalist O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 4 of the way up the tail) were secured and not damaged or exposed during sampling. We collected morphometric measurements as an indicator of individual condition and fitness. Although we included 9 parameters for females and 13 for males, only disc width (WD; mm) is presented here. We employed t-tests to detect sex-based differences in size (WD). To determine if habitat type (mangrove creek/sand flat) could be used to predict size, and by proxy, possible life-history stage (i.e., juvenile/ adult), we used a linear model with size as the dependent variable and habitat type as the independent variable to compare individuals caught in and out of mangrovecreek systems. We harvested, stored in 90% ethanol, and froze white muscle tissue from the pelvic fin, which we used to verify our identifications by subsequent subsampling to amplify the cytochrome oxidase I gene and cross-referencing the results with the Basic Local Alignment Search Tool (BLAST) database. We employed the R progam to conduct t-tests (R Core Team 2013) and Lme4 package in R to carry out linear analysis (Bates et al. 2015). Results We documented a total of 95 individuals from 32 sites between January 2015 and September 2016 and caught 74% (n = 70) of these for further data collection; 33 were females and 37 were males. We captured rays from 25 sites spanning an area 115 miles from Great Exuma Island in the south, to Ship Channel Cay in the North, and 40 miles eastward to Hartford Creek in southern Eleuthera. Disc width ranged from 228 mm to 1472 mm (Table I). We documented the smallest individuals (WD ± SE) from the northern Exumas (527 mm ± 60; Fig. 2B) and Eleuthera (571 mm ± 34); the largest individuals sampled were from the southern Exumas (1168 mm ± 48; Fig. 2C). DNA barcoding of 8 samples confirmed our species identifications with 86–94% identification confidence from BLAST. Mean size (WD ± SE) was 672 mm ± 61 for females and 714 mm ± 55 for males; this difference was not statistically significant (P = 0.3, df = 66). Fifty-eight individuals (83%) captured in or next to mangrove-creek systems had a mean WD of 560 mm ± 33 compared to a mean of 1080 mm ± 70 for individuals sampled on sand flats and bars. Linear modelling further demonstrated that habitat type was a significant factor determining size class (P < 0.01, df = 18); smaller individuals were predictably located in creek systems and larger individuals were located on the banks systems. Aggregation We observed an aggregation of 17 large (estimated 1500–2000 mm WD) individuals at Hummingbird Cay in February 2016 (Fig. 2D). Individuals were loosely aggregated over a small area (~400 m2), making it possible to count them from a boat. The rays were in close proximity to one another and were a mixed-sex aggregation (10 males, 7 females), with several individuals resting on top of one another in a “stacking” formation. We noted no obvious behaviors (i.e,. feeding or mating) during the 60-min observation time. Caribbean Naturalist 5 O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 Table 1. Demographic data for each sample location and site. WD = disc width and *denotes overall sample mean and SE for each location Mean Location/site Latitude Longitude n Male Female WD (mm) SE (mm) Eleuthera Boathouse cut 24.833598 -76.330598 1 0 1 1201 0 CEI Beach 24.820601 -76.314344 1 0 1 620 0 Deep Creek 24.76991 -76.277286 14 6 8 500 28 Hartford Creek 24.41922 -76.122969 4 1 3 539 75 Kemps Creek 24.812635 -76.305345 4 4 0 541 11 Paige Flat 24.819477 -76.303157 1 0 1 654 0 Wemyss Bight 24.71888 -76.221936 7 5 2 539 25 Plum Creek 24.757298 -76.258508 1 1 0 510 0 Marker Bar 24.856475 -76.321738 1 0 1 1289 0 Total 34 17 17 571* 34* Northern Exumas Highbourne Cay 24.713999 -76.823724 2 0 2 627 157 Norman's Cay 24.64232 -76.81119 3 0 3 864 304 Shroud Cay 24.528339 -76.792584 2 1 1 703 208 Ship Channel Cay 24.827552 -76.819704 2 2 0 582 151 Warderwick Wells 24.392276 -76.627631 3 1 2 230 2 Great Guana Cay 24.113657 -76.40446 1 0 1 390 0 Samson Cay 24.21671 -76.471034 3 3 0 520 9 Pipe Cay 24.236362 -76.512614 3 3 0 403 85 Compass Cay 24.263358 -76.514775 2 1 1 397 46 Total 21 11 10 527* 60* Southern Exumas Bowe Cay 23.454185 -75.965612 1 1 0 1256 0 Brigantine Cay 23.813773 -76.139282 1 1 0 875 0 Gold Ring Cay 23.786309 -76171588 1 1 0 1340 0 Green Turtle Cay 23.476861 -75.887402 1 1 0 1060 0 Hummingbird Cay 23.463602 -75.945887 7 5 2 1277 33 Hog Cay 23.461536 -75.861545 3 1 2 1094 89 New Cay 23.726053 -76.17698 1 0 1 770 0 Total 15 10 5 1168* 48* Observations Only Cat Island 24.148176 -75.523865 2 Schooner Cays 24.903608 -76.364815 1 Hummingbird Cay 23.458010 -75.941080 17 Rock Sound 24.827190 -76.239465 1 Starved Creek 24.817428 -76.185644 1 Stocking Island 23.518888 -75.756320 2 Bimini 25.736644 79.227742 1 Total 25 Discussion Previous to our work, the presence of the Caribbean Whiptail Stingray in The Bahamas was documented by an individual specimen collected in 1968; thus, this area has been excluded from databases that list the species’ range (e.g., CharvetCaribbean Naturalist O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 6 Almeida and de Almeida 2006, www.FishBase.org, Last et al. 2016). Until now, no verified sightings at any Bahamian locality have been reported in the intervening 48 years since the first observation was made. It is possible that this species may have been consistently misidentified as Hypanus (= Daysatis) americana (Hildebrand & Schroeder) (Southern Stingray) or Bathytoshia (= Dasyatis) centroura (Mitchill) (Rough-tail Stingray); all 3 are large-bodied demersal species and research has overlooked Caribbean Whiptail Stingray in The Bahamas because there have been no previous records. Life-history data pertaining to this species is lacking; however, we present habitat association by size, and our data demonstrate that compared to larger individuals, smaller individuals are more likely to be associated with mangrove creeks. Although these data do not correlate size to life-stage, evidence of other similar species using inshore areas as nurseries before migrating offshore support the theory that Caribbean Whiptail Stingrays may have the same behavior. For example, Dale and colleagues (2011) showed via stable-isotope analysis that juvenile Bathytoshia (= Dasyatis) lata (Garman) (Brown Stingray) foraged within Kaneohe Bay, Hawaii, before the onset of sexual maturity that was linked with an offshore habitat occupation, and Cerutti-Pereyra et al. (2014) demonstrated long-term use of coastal lagoons and inter-tidal areas in Australia by 4 species of juvenile stingray via acoustic telemetry. There is anecdotal evidence of aggregations of individuals in Himantura spp., the genus within which the Caribbean Whiptail Stingray was until very recently classified, although ours is the first and only report of such group association in this particular species. Group resting usually occurs for a specific reason; for example, it can be an effective anti-predator strategy (Semeniuk and Dill 2006), or provide increased foraging opportunities when resources are scarce (Johnson et al. 2002). Mechanisms driving this aggregation are not clear, and it may have been simply refuging behavior in order to conserve energy, as postulated by Hamilton and Watt (1970). Observations presented here provide the most comprehensive evidence for Caribbean Whiptail Stingray in The Bahamas and clearly support the concept of a formal range extension in this species. Elasmobranchs that occupy shallow waters are, by nature, more susceptible to extrinsic pressure, such as increased fishery access, because these environments represent the interface between terrestrial and marine systems. These pressures can exacerbate extinction risk, particularly for larger-bodied species (Dulvy et al. 2014). The fragmented nature of The Bahamas Archipelago creates a gradient whereby localized or site-specific habitat degradation may impact coastal elasmobranch species and their ability to move among habitats critical to their life history. For example, deep ocean channels and basins separate many islands, providing potential barriers to dispersal, which is particularly relevant for live-bearing demersal fishes such as stingray s. According to Dulvy et al. (2014), almost one third of threatened sharks and rays are susceptible to habitat degradation in the coastal, estuarine, and riverine habitats that characterize island nations such as The Bahamas. Legislation to protect the ecoCaribbean Naturalist 7 O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 logical significance of coastal resources in The Bahamas is far from adequate, and no dedicated legislation exists for the protection of mangroves. Updating locality records for data-deficient species in these habitats is critical for the establishment of scientifically defensible baselines to create legislation, particularly if this species is spending its entire life cycle in The Bahamas where we found smaller individuals in creeks or mangrove-fringed embayments and larger rays in flats and rocky coastlines. We plan future work with these subpopulations that will assess genetic connectivity, the potential of creek systems to serve as nursery habitats, long-term site fidelity and growth rates via mark–recapture, and trophic status via stable-isotope analysis. Acknowledgments We thank The Hummingbird Cay Foundation for in-kind support by allowing access to their land for wider sampling in the southern Exuma Cays and The Rufford Foundation and The Cape Eleuthera Foundation for partially funding this study. We are grateful to A. Schultz, G. Burruss, L. Wallace, A. Feiler, A. Brown, A. Waldman, D. Montgomery, S. Burnside. K. Luniewicz, C. Bauer, C. White, R. Hallinan, N. Firing, D. Cardeosa, and Spring and Fall 2015 Island School classes. We are indebted to O. Shipley for creating the Figure 1 map. We appreciate Basil and Chris Minns for being so forthcoming with historical accounts and literature pertaining to the first Caribbean Whiptail Stingray recorded from The Bahamas. Literature Cited Bates, D., M. Maechler, B. Bolker, and S. Walker. 2015. Fitting linear mixed-effects models using lme4. Journal of Statistical Software 67(1):1–48 Böhlke, J.E. 1969. The Caribbean Stingray. Frontiers 33:19–21. Brooks, D.R. 1977. Six new species of tetraphyllidean cestodes, including a new genus, from a marine stingray, Himantura schmardae (Werner, 1904) from Colombia. Proceedings of the Helminthological Society of Washington 44:51–59. Cerutti-Pereyra, F., M. Thums, C.M. Austin, C.J.A. Bradshaw, J.D. Stevens, R.C. Babcock, R.D. Pillans, and M.G. Meekan. 2014. Restricted movements of juvenile rays in the lagoon of Ningaloo Reef, Western Australia: Evidence for the existence of a nursery. Environmental Biology of Fishes 97:371–383. Charvet-Almeida, P., and M.P. de Almeida. 2006. Himantura schmardae. The IUCN Red List of Threatened Species 2006. Available online at http://dx.doi.org/10.2305/IUCN. UK.2006.RLTS.T60161A12300074.en. Accessed 14 March 2016. Compagno, L.J.V. 1999. Checklist of living elasmobranchs. Pp. 471–498, In W.C. Hamlett (Ed.). Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes. Johns Hopkins University Press, Baltimore, MD, USA. 528 pp. Dale, J.J., N.J. Wallsgrove, B.N. Popp, and K.N. Holland. 2011. Nursery-habitat use and foraging ecology of the Brown Stingray, Dasyatis lata, determined from stomach contents, bulk, and amino acid stable isotopes. Marine Ecology Progress Series 433:221–236. Deardorff, T.L., D.R. Brooks, and T.B. Thorson. 1981. A new species of Echinocephalus (Nematoda: Gnathostomidae) from neotropical stingrays with comments on E. diazi. The Journal of Parasitology 67:433–439. Dulvy, N.K., S.L Fowler, J.A. Musick, R.D. Cavanagh, P.M. Kyne, L.R. Harrison, J.K. Carlson, L.N. Davidson, S.V. Fordham, M.P. Francis, and C.M. Pollock. 2014. Extinction risk and conservation of the world’s sharks and rays. Elife 3:e00590. Caribbean Naturalist O.R. O’Shea, C.R.E. Ward and E.J. Brooks 2017 No. 38 8 Gadig, O.B.F., and U.L. Gomes. 2003. Família Somniosidae. P. 160, In N.A. Menezes, P.A. Buckup, J.L. Figueiredo, and R.L. Moura. (Eds.). Catálogo das Espécies de Peixes Marinhos do Brasil. São Paulo. Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil. Hamilton, W.J., and K.E. Watt. 1970. Refuging. Annual Review of Ecological Systems 1:263–287. Johnson, D.D., R. Kays, P.G. Blackwell, and D.W. Macdonald. 2002. Does the resource-dispersion hypothesis explain group living? Trends in Ecology and Evolution 17:563–570. Last, P., W. White, M. de Carvalho,B. Séret, M. Stehmann, and G. Naylor. 2016. Rays of the World. CSIRO Publishing, Clayton, Australia. P. 655 NPOA-Sharks. 2015. National plan of action for the conservation and management of Chondrichthyes in the Republic of Cuba. Ministry of the Food Industry, Havana, Cuba. 48 pp. R Core Team. 2013. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Available online at http://www.R-project. org/. Salvat Torres, H., N. López-Fernández, and F. Pina-Amargós. 2012. Ictiofauna del archipiélago Jardines de la Reina, Cuba. Revista de Investigone s Marinas12:54–65. Semeniuk, C.A., and L.M. Dill. 2006. Anti-predator benefits of mixed-species groups of Cowtail Stingrays (Pastinachus sephen) and Whiprays (Himantura uarnak) at rest. Ethology 112:33–43. Smith-Vaniz, W. F., and E.B. Böhlke. 1991. Additions to the ichthyofauna of the Bahama Islands, with comments on endemic species. Proceedings of the Academy of Natural Sciences of Philadelphia 143:193–206. Stehmann, M, J.D. McEachran, and R. Vergara. 1978. Dasyatidae. In W. Fischer (Ed.). FAO Species-Identification Sheets for Fishery Purposes. Western Central Atlantic (Fishing Area 31) Vol. 1. Food and Agriculture Oorganization of the United Nations, Rome, Italy.