Category Archives: stingrays

Dr Owen O’Shea visits the Florida Fish and Wildlife Conservation Commission

The ongoing collaboration between the Cape Eleuthera Institute and the Florida Fish and Wildlife Conservation Commission (FWWCC) was recently further endorsed with a visit by Research Associate Dr Owen O’Shea to the FWWCC headquarters in St. Petersburg, Florida. Much of Dr O’Shea’s work on stingray genetics is in collaboration with Dr Liz Wallace, postdoctoral research fellow at the commission and so this trip served as an analytical opportunity for Owen to conduct lab work with Dr Wallace in order to process DNA samples collected over the past 12 months.

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This research project is in the final stages of completion, after Owen collected 70 samples from the rare, elusive and recently re-described Caribbean whiptail stingray Styracura schmardae across multiple spatial scales in the central Bahamas. This work is the first of its kind in this species, and will attempt to discern dispersal potential and gene flow across restricted temporal periods, for example, in assessing sibling and parentage relationships, rather than an historical radiation.

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This work is important, because in fragmented habitats, such as The Bahamas, barriers to gene flow and dispersal are realized, particularly among island chains, separated by deep ocean basins. This provides challenges for live bearing fish species, further exacerbated by conservative life histories; so understanding these dynamics and potential migratory corridors will enable us to further discern the importance of these coastal environments.

Prey discrimination in yellow rays: project update

In the last month, Research Technician Maggie Winchester began behavioral trials of yellow rays (Urobatis jamaicensis) as part of her independent project, under the supervision of Dr. Barbara Wueringer of James Cook University, Australia, and Dr. Owen O’Shea of the Cape Eleuthera Institute (CEI). This project aims to address the capacity of the electric sense utilized by all elasmobranchs, as it pertains to their foraging strategy. Specifically, Maggie and the team using experimental manipulations to assess to what extent prey type can be ‘discriminated’ by isolating electric sensory mechanisms alone.

Yellow ray close up
Yellow ray close up

The yellow ray is one of the most ubiquitous and commonly encountered elasmobranchs throughout the Caribbean region and is a regular visitor to the shelf and patch reefs adjacent to CEI. It is a small-bodied benthic ray that lives in seemingly mixed sex aggregations and is very easy to catch in shallow water with two dip nets by snorkeler. So far, the team has successfully captured and transported 19 rays to the wet lab at CEI, where they have all undergone behavioral trials, and been successfully returned to their capture sites after 24-hours observation.

A yellow ray in one of our wet lab holding tanks awaiting trails
A yellow ray in one of our wet lab holding tanks awaiting trials

During the experimental trials, individual rays are presented with two concealed prey types that are known to be part of their diet based on a study by CEI currently in review for publication. These two prey choices are concealed in agar, masking visual, chemical and gustation cues and allowing for detection solely through electro-sensory means.

This work will allow a clearer and more concise evaluation on the specific role the ampullae-lorenzini have in discriminating a specific type of prey, and raises questions on whether these rays actively choose one prey type over another.

European Elasmobranch Association meets in Bristol

Over the weekend of the 28-30th October the European Elasmobranch Association met for its annual conference hosted by The Shark Trust in Bristol, England. Daniel Montgomery, a graduate student with Newcastle University, attended the conference to present his research focussing on the influence of temperature on habitat use of southern stingrays. This research was conducted at the Cape Eleuthera Institute between February and June 2016 in collaboration with Dr. Owen O’Shea and formed a research class for the spring 2016 Island School semester.

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The conference was attended by 160 delegates from 22 countries. Over the three days 67 oral presentations were delivered on a variety of themes with talks giving an overview of current research being conducted around the world. The conference is known for its broad focus with notable presentations ranging from taxonomy and isotopic analysis of deep sea sharks to the classification of nursery habitats in tropical mangroves.  In addition keynote addresses were delivered on subjects focusing on improving management and conservation of elasmobranchs globally. The conference gave a fantastic opportunity to meet other shark and ray researchers and promote the important work conducted at the Cape Eleuthera Institute alongside other research institutes.

Dan has just been awarded a pass with distinction from Newcastle University for his thesis titled Temperature preference and thermal niche of the southern stingray (Dasyatis americana) in South Eleuthera, The Bahamas. Dan is currently working towards his PhD at Exeter University and we wish him every success!

Graduate student update from the Stingray Research Group

Molly Meadows and Ethan Wrigglesworth have joined the team as part of the Masters of Research data collection from Exeter University in the UK, under the supervision of Dr. Owen O’Shea and Dr. Lucy Hawkes. The university has been visiting CEI every January for three years as part of their field course module, creating a fantastic bond between the two institutions. So it is very exciting to have students from Exeter studying their Masters with CEI for the very first time, further expanding our relationship and connection.

Ethan, Molly and the stingray team work up a large female southern stingray.
Ethan, Molly and the stingray team work up a large female southern stingray.

Both Molly and Ethan are researching stable isotope analysis on the two species of stingrays here in Eleuthera, the Caribbean whiptail and southern stingrays. Stable isotopes can be used to peek into the diet and ‘trophic status’ of an organism over different timescales. It basically follows the general rule of “you are what you eat”; all organic tissue has an isotopic value and, once ingested, that value can then be identified within the consumer’s body tissues. They will be collecting body tissue samples from both species of stingray, as well as diet and habitat samples, all of which will be analysed back at Exeter’s facilities in the UK. They will also be studying captive rays in the wet labs here at CEI, discerning how quickly isotopic values from manipulated prey sources are assimilated into different body tissues.

Molly and Ethan brief an educational program before going out into the field (Photo by Catherine Argyrople)
Molly and Ethan brief an educational program before going out into the field (Photo by Catherine Argyrople)

This research forms part of The Island School Applied Scientific Research Class and students will be directly assisting with data collection whilst producing a side project on dietary partitioning between the two ray species.Stingrays are remarkable, ancient creatures, which play key roles as mesopredators and bioturbators within their environment, keeping ecosystems stable and healthy. Despite this, not much is actually known about this group of around 90 species, particularly the species focused on in this study. Therefore, any research on these creatures is vital, not only for the conservation of the individual species, but for the systems they inhabit as a whole. Understanding these stingrays place in the food chain will help quantify their impacts on local fisheries and ecosystems allowing more effective conservation methods to be employed.

A female southern stingray is released after being sampled for stable isotopes
A female southern stingray is released after being sampled for stable isotopes

 

American Elasmobranch Society meets in New Orleans

The American Elasmobranch Society recently met in New Orleans for their annual meeting, attended by an international collective of shark and ray scientists to discuss current and ongoing work in this very eclectic field. The Cape Eleuthera Institute was represented by Oliver Shipley and Dr. Owen O’Shea of the Shark Research and Conservation Program, both giving oral presentations to a wide range of scientists from all over the world. Oliver’s presentation focused on novel methods for post-capture release of a small bodied deep-sea shark – the Cuban dogfish – and how novel approaches may increase survivorship during by-catch events. Owen spoke of the recently ‘re-discovered’ Caribbean whiptail stingray and discussed its contemporary distribution in The Bahamas and implications for management.

Dr, Owen O'Shea during his presentation on Caribbean whiptail stingrays
Dr. Owen O’Shea during his presentation on Caribbean whiptail stingrays

The week spent in New Orleans was a huge success, with the convening of several meetings and discussions pertaining to the global fin print project and a whole day dedicated to a global sawfish research symposium. Among some of the other stand out talks were the very first satellite tracking of manta rays conducted in Sudan, juvenile white shark movement in California and challenges for management of large ranging sharks, such as the great hammerhead and oceanic whitetip. It was a fantastic week with many old relationships rejuvenated, and the fostering of new ones cemented, with collaborative studies already having been discussed.

Operation Wallacea

During the course of a six-week program, three students representing Operation Wallacea (Marcus Griffiths of the University of Nottingham, Rob McCalman of the University of Portsmouth and Lucy Arrowsmith of the University of Cardiff) have teamed up with Dr. Owen O’Shea at The Cape Eleuthera Institute to investigate the benthic habitat diversity of various creek systems around Eleuthera, The Bahamas. This project aims to establish the relationships between environmental and physical characteristics of the recently ‘re-discovered’ Caribbean Whiptail Stingray, Himantura schmardae.  As a meso-predatory species, these stingrays provide an important link between apex predators and the benthic organisms they prey upon. An abundance of this species within creek systems provides a good indication of ecosystem health.

The Ray team surveying Deep Creek - A very large and biologcally rich ecosystem bordering the deep Exuma Sound
The Ray team surveying Deep Creek – A very large and biologcally rich ecosystem bordering the deep Exuma Sound

The team are currently in the process of completing benthic habitat analysis on four sites: Deep and Wemyss Bight Creek (Atlantic/Exuma Sound) and Kemps and Starved Creek (Grand Bahama Bank). This project is collecting data using a 1m2 quadrat to assess the percentage cover of flora and fauna species found in these locations, so far completing a total of 274 quadrats over a 2.6Km2 combined study area. In addition, sediment cores; sediment depth; water salinity; dissolved oxygen and water temperature are being collected at each location to gather a broader insight into the habitual preference of juvenile Himantura schmardae that appear to be utilizing these creeks on a long term basis.

The Caribbean whiptail stingray - specimen from Deep Creek
The Caribbean whiptail stingray – specimen from Deep Creek

The aim of the investigation is to determine the relationship between the creek environments and the presence or absence of this relatively elusive stingray. Additionally the morphological, sexual and feeding characteristics will provide insight into the potential role of these marine systems as possible nursery sites. As a relatively new re-discovery for The Bahamas, this research could provide critical information towards development of successful conservation plans, and fine-tuning the coverage of marine protection areas (MPAs) as declared by The Caribbean challenge for the Bahamas in 2008.

Kemps Creek on the Banks side - a smaller, mangrove fringed creek
Kemps Creek on the Banks side – a smaller, mangrove fringed creek

Graduate student Dan Montgomery working on stingray research at CEI

The team take measurements of a stingray prior to fitting an iButton
The team take measurements of a stingray prior to fitting an iButton

In the past week, members of the Stingray Research Team from the Shark Research and Conservation Program (SRCP) have begun work on a new project investigating the thermal ecology of southern stingrays (Dasyatis americana). As part of the research for this new study, the stingray team, assisted by gap year students and interns, fitted southern stingrays with temperature recorders. These recorders monitor seawater temperatures experienced by stingrays every 15 minutes for 3 weeks.

Southern stingray fitted with iButton swims away after release
Southern stingray fitted with iButton swims away after release

All sharks and rays are ectotherms, meaning their internal body temperature is controlled by the temperature of the environment around them. As such, changes in seawater temperature can impact the physiological processes of the animals, which may mean that temperature differences among the coastal waters of Eleuthera influence the areas which rays use.

Surgical needles are used to make holes in the stingrays tail in order to attach the iButton
Surgical needles are used to make holes in the stingrays tail in order to attach the iButton

Over the next 4 months, the study aims to tag 50 rays at both Marker Bar and the Schooner Cays, as well as conduct laboratory experiments with rays to identify thermal preferences. Also, temperature tags fitted to wild individuals will aid in understanding whether temperature is a driver of habitat selection in this ray species. Quantifying the drivers for habitat use of these ecologically important species is vital to effectively manage coastal marine habitats. The research is led by Daniel Montgomery, a postgraduate research student at Newcastle University, who is working in collaboration with Dr. Owen O’Shea and CEI.

 

HUMMINGBIRD CAY STINGRAY EXPEDITION

Four members of the Cape Eleuthera Institute (CEI) community, including members of the Shark Research and Conservation Program (SRCP) and the reef ecology team, ventured down to Hummingbird Cay in the Exumas to further Dr. Owen O’Shea’s study on the elusive Caribbean whiptail stingray (Himantura schmardae). Very little is known about this species, but it is vital to elucidate information pertaining to their biology and ecology in order to calculate effective conservation methods. The main goal of this project is to determine connectivity and gene flow of the Caribbean whiptail stingray by collecting tissue samples from individuals across multiple spatial scales.

The stingray team with a large male whiptail ray at Hummingbird Cay
The stingray team with a large male whiptail ray at Hummingbird Cay

Stingrays are one of the most influential architects to their ecosystems, as they impact their surroundings in numerous ways. They hold an integral position in coastal food webs, acting as predators to animals in lower parts of the food chain and prey to those higher up, such as sharks. Their physical movements involve bioturbation – meaning reworking and suspending of sediments. This oxygenates the sediment around them and re-suspends nutrients, promoting primary productivity. Although there are gaps in our understanding regarding the behavioral tendencies of the Caribbean whiptail stingray, they are likely significant agents within their ecosystems.

Dr. Owen O'Shea holding one of the smaller rays during an 'in-water' workup

 

The expedition began with four extremely successful days in the field; with near perfect weather conditions, the team caught 13 rays over a spatial scale exceeding 35 miles – something critical when evaluating gene flow of a species. Nine of these were male and all rays ranged from 80cm disc width to around 140 cm with all estimated as being mature or sub adult – an inverse trend in the population sampled from south Eleuthera.

Day five offered a frustrating morning without a single ray observed due to strong northerly winds, churning up the fine sediments, seemingly synonymous with this species. However, it wasn’t long before the team moved on to the leeward side of one of the islands and stumbled across an aggregation of 17 whiptail rays. The group consisted of very large adult stingrays, most of which were resting or casually mobile and seemed unflustered when we slipped quietly into the water for a closer inspection. Until now, no records exist in the literature of aggregations in this species from The Bahamas, and we can only speculate about how common this type of aggregation may be for this species. What is certain is that it was an honor to witness such a substantial group of these huge animals.

Whiptail aggregation from the surface

Between last year’s expedition and this most recent trip, DNA and stable isotope information has been collected from 15 individuals from this location and 23 from Eleuthera. This study will continue to grow as samples are expected to be collected over a larger spacial scale in the months to come, filling in the gaps from the rest of the Exuma chain.

We would like to acknowledge the Rufford Foundation for funding this work and making this expedition possible. Also, thank you to the exceptional team at Hummingbird Cay for welcoming us so hospitably and for helping to make our trip so successful.

Another outreach event with the Stingray Team!

Members of the Stingray Research Group from the Cape Eleuthera Institute’s Shark Research and Conservation Program have recently completed two days of outreach on Great Exuma. Following on from the highly successful Hummingbird Cay research expedition, the team, in collaboration with The Exuma Foundation and LN Coakley High School in Moss Town, took five students out to learn about stingrays at a marine reserve East of Georgetown.

Stingray Team with students from LN Coakley High School
Stingray Team with students from LN Coakley High School

The five students that spent the day with us were already incredibly knowledgeable about rays and their importance in regulating and maintaining healthy marine ecosystems. so we had a head start as we headed across Elizabeth Harbour towards Stocking Island. This designated marine reserve has long stretches of white sand beaches and little ‘hurricane holes’ naturally formed over time, allowing us to explore semi-enclosed ponds and quiet bays.

Upon arrival, the students were quizzed about rays and were given a safety talk before we set off looking for animals to capture and collect information from. While it was slow starting, we eventually caught a very small, immature female southern ray. Two of the students donned surgical gloves, and under the instruction of Research Technician Chris Ward, were able to complete a whole work up beneath the gaze of a dozen or so tourists that had gathered on the beach to watch what was happening.

The team working up a ray with two young students and toursits watching on
The team working up a ray with two young students and toursits watching on

 

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A busy week with The Island School Research Symposium and Parent’s Week

Last Thursday was The Island School Research Symposium! It is a highlight of Parent’s Week, and a time for parents to hear about the good work being done by their sons and daughters. Throughout the semester, The Island School students have collaborated with CEI researchers, contributing to ongoing research projects. They have been studying various ecosystems around Eleuthera, including inland ponds, the pelagic zone, the deep sea, shallow water sandbars, and tidal creeks .

Dr. Craig Dahlgren discussing the current state of coral reefs in The Bahamas.
Dr. Craig Dahlgren discussing the current state of coral reefs in The Bahamas.

 

In all, nine projects were presented, and Dr. Craig Dahlgren, Senior Research Scientist for the Bahamas National Trust, concluded the event with a talk on the state of coral reefs in The Bahamas. All nine projects are being featured on our Instagram (@CEIBahamas) and Facebook pages, so please check them out for more details on the amazing research done this semester!