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stingrays

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 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 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

Graduate student Dan Montgomery working on stingray research at CEI

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

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

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

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

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 then walked around the corner to local tourist spot Chat ‘N’ Chill, where a conch stand attracts southern and whiptail rays to the shallows. The team then scooped up a larger female ray who had been cruising for scraps and again, allowed students to get up close with the ray with more tourists and locals looking on, who were equally as captivated as the students.

When it was time to catch the water taxi back to Exuma, the students were all quizzed on what they had learned, and all of them had said that not being afraid of these animals was something they would take away. Most of the group were nervous of rays in the morning, but at the end of the day were handling wild rays and speaking confidently about them and their importance within these fragile marine ecosystems.

The team would like to acknowledge Catherine Booker from the Exuma Foundation for facilitating this outreach event and LN Coakley High School for donating five, willing participants to catch and learn about wild stingrays!

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.

 

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!