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.
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.
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.
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.
Nassau grouper is an economically important species in The Bahamas. Due to heavy fishing pressure, there have been marked decreases in their population sizes, especially noticeable during their spawning season. The spawning season takes place during the winter months, from December to the end of February, and the aggregations occur during the full moon. Dr. Kristine Stump from the Shedd Aquarium has been monitoring Nassau grouper in The Bahamas to track their movements to spawning aggregations, as well as to quantify the number of Nassau grouper at these historical spawning sites.
The researchers that took part in the Nassau grouper work in front of the Shedd Aquarium vessel
This January, the Shedd Aquarium research vessel, The Coral Reef II, travelled to Long Island, to historical spawning sites, with a representative of The Cape Eleuthera Institute on board, to assist Dr. Stump with her research. Throughout the week-long journey, the researchers on board performed dive surveys to quantify spawning stock size at one specific site. Unfortunately, very few Nassau grouper were aggregating at the site during the times of the surveys; at most 20 were noted on one survey. Illegal fishing was occurring at the time the vessel reached the site, which could explain the decreased abundance of the grouper. Poor weather conditions prevented the researchers from performing surveys on the night of the full moon, so it is unclear if numbers increased during the spawning event. Continue reading →
Students cleaning off the seine net after a long day’s work
Recently, St. Thomas Aquinas High School from Dover, New Hampshire helped conduct research with the CEI sea turtle research team in Winding Bay. Although the weather was uncooperative on Friday while the group was seining, they came out strong with the capture of five green sea turtles in their first attempt. Seining is a method used by several research teams at CEI that involves a very long net that temporarily encloses the animals inside.
The group on Saturday had to put in a little more effort as it took five seining attempts to finally capture three green sea turtles!
Students take the curved carapace length (CCL) of one of the turtles
One turtle that was captured, Kyra, had its left rear flipper almost completely detached. The wound was healed and the flipper still had some movement. What caused the damage is unknown, but Kyra is lucky to have kept this limb! Green turtles don’t typically use their rear flippers much except for maneuvering while swimming, and females use them for digging a nest.
A turtle being measured
Both groups had the opportunity to experience the challenge it is to catch sea turtles and keep them steady to take measurements! It was all worth it as one student said, “This was the best day so far!”
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
On Wednesday, 3rd February, the Shark Research and Conservation Team captured and sampled only the fourth ever Great Hammerhead shark (Sphyrna mokarran) caught off of Eleuthera in the entirety of the program’s ten-year operation. During a shark ecology and handling class for the Cape Eleuthera Institute’s Gap Year Program, led by Research Assistant Oliver Shipley and Educational Assistant Cameron Raguse, the students were able partake in a rare experience in handling one of the most data-deficient sharks found in The Bahamas. Increasing our understanding of sharks in The Bahamas is important to ensure the most applicable and effective management of these keystone apex predators.
The animal is safely secured prior to the workup
Hammerhead sharks (Sphyrnidae) are a morphologically distinct family of elasmobranchs comprising of nine species, and are found in temperate and tropical waters around the globe. They have evolved a unique dorso-ventrally compressed and laterally expanded cephalofoil that allows them to expand their field of sight and pin down prey items such as stingrays. Their common diet consists of molluscs, annelids, crustaceans, teleosts, and even other elasmobranchs. Great Hammerhead’s (Sphyrna mokarran) reach up to 3.5 m and weigh up to 230 kg. They are a highly migratory and solitary species that lives in coastal-pelagic waters near continental shelves. They are known to migrate from tropical to more temperate waters during the summer months to seek cooler water, and have been observed using offshore habitats including deep-water.
In The Bahamas, the biological and economic importance of sharks has been well recognized, leading to the 2011 amendment to the Fisheries Resources (Jurisdiction and Conservation) Act (Chapter 244), establishing The Bahamas as a National Shark Sanctuary. This declaration has provided thorough protection for a plethora of shark species, through the banning of commercial fishing and transport of shark related products into or outside of the approximately 630,000km2 that encompass The Bahamas.
The hammerhead shark is tagged with a dorsal identification tag.
This Great Hammerhead was captured during one of the shark team’s routine experimental longline surveys. The goal of this work is to gather tissue samples, such as muscle, fin and blood from a wide range of coastal elasmobranchs, to determine their diet, and subsequently the scale to which they perform important ecological controls. The experimental longline consists of a 500m mainline equipped with 40 gangions which terminate in baited hooks and are supported by flotation buoys. Lines are soaked for a total of 90 minutes before being retrieved.
The hammerhead shark is safely released in under 5 minutes
In addition to collecting tissue samples, the team also took measurements, a DNA sample, and attached two identification tags. This work-up procedure was completed in less than five minutes before the animal was safely released. A video of the release can be found on our Instagram page (@ceibahamas).
A spawning aggregation of thousands of bonefish (Albula vulpes) was recently filmed in South Eleuthera. Bonefish make monthly migrations of up to 80 km (50 miles) to form spawning aggregations!
CEI’s Flats Ecology and Conservation Program is currently studying the spawning migrations of bonefish, which support a catch-and-release flyfishing industry worth over $141 million annually in The Bahamas. To view our most recent publications on this economically important species, please visit our website www.ceibahamas.org.
A juvenile tiger shark (Galeocerdo cuvier) – one of three captured on camera
Last week, four members of the Shark Research and Conservation Program (SRCP) travelled to Nassau, New Providence to participate in a global effort to assess the abundance and diversity of apex predators on coral reefs, termed The Global Finprint Project (GFP). The GFP is a Paul G. Allen initiative, facilitating global cooperation between various scientific institutions. The main goal is to collect abundance and diversity data on reef-associated elasmobranchs in order to provide a valuable baseline pertaining to their current population trends. The call to assess the health of these populations is critical, as many are either listed by the IUCN as data deficient, or are showing rapid declines. The GFP is the largest study of its kind ever undertaken, and the SRCP is responsible for surveying a multitude of sites across the greater Caribbean.
Abundance and diversity data is collected through a scientifically accepted, non-invasive methodology, Baited Remote Underwater Video (BRUVs). BRUV’s consist of a camera, weighted frame, and bait arm, which provides a concentrated plume, designed to attract predators. BRUVS are deployed for 90-minute ‘soak’ periods in order to allow enough time for the plume to travel and disperse within the water column. Over seven days the team collected over 100 hours of video from two regions (south west, and north east) off Nassau, New Providence, from depths ranging from 2m to 30m.
Two Caribbean reef sharks (Carcharhinus perezi) feeding from a bait crate
Preliminary assessment of the video data suggest a diverse array of sharks and other predators associated with reefs around Nassau. The team identified hammerhead, Caribbean reef, blacknose, nurse, and tiger sharks, as well as southern stingrays, amberjack, turtles and a Spanish mackerel. Failing to robustly assess the diversity and the relative abundance of these animals has large implications for their effective management, and data collected from Nassau provides an intrinsic step to facilitating the success of this global conservation effort. Finally, our team would like to extend large thanks to Stuart Cove’s for their generous hospitality during this trip.
A southern stingray (Dasyatis americana) passing a BRUV unit
Georgie Burruss deploys a VEMCO receiver while on SCUBA.The transmitter is about to be implanted into the fish through a small incision in the body cavity.
Previous research indicates that bonefish migrate up to 80 km from shallow flats and tidal creeks to deeper water to spawn during the full and new moons. At these locations, bonefish gather in schools of hundreds to thousands of fish, forming spawning aggregations. To date, migration corridors and spawning aggregations have been located in South Eleuthera, Abaco, Andros, and Grand Bahama, and this information was used to create national parks on Abaco and Grand Bahama. The purpose of this telemetry study is to identify bonefish spawning aggregations and migration corridors around the island of Eleuthera. Information generated by this research can be used by the Department of Marine Resources and BNT to designate marine parks on Eleuthera, which will help The Bahamas meet the goal of protecting 20% of their marine environments by 2020.
Georgie Burruss is suturing an anesthetized bonefish after implanting a transmitter into the fish.
Last Friday, Deep Creek Middle School’s Grade 7 joined Georgie Burruss, CEI Research Assistant, for a snorkel through Page Creek as part of the School Without Walls program. The focus of Grade 7′s School Without Walls program this year is human impacts on the environment. Nearshore environments, especially mangrove creeks, serve as a great educational tool for displaying how even small-scale coastal development can be detrimental to coastal habitat.
Students raise their hands to answer Georgie’s questions about the mangrove ecosystem
The students drifted with the incoming tide into the creek, practicing fish ID that they learned that morning with Liz Slingsby, Director of Summer Term and Gap Year Programs. At the end of their first snorkel through the creek, the students were able to successfully ID over a dozen fish species and discussed how mangroves act as nursery grounds for ecologically and economically important species such as snapper and lemon sharks.
Flats intern helps some of the students wade upstream
With the excitement of snorkeling and floating with the current, the students quickly rushed to float down again. At the end, the group met and discussed how humans might affect mangrove creek systems. The students quickly recognized pollution and habitat degradation as some of the major impacts that humans can have on these important systems. As the group walked out of Page Creek, they observed how even a short beach access road can divide a creek, limiting available habitat.
Students eager to answer Georgie’s quetions.
CEI researchers look forward to spending more time with DCMS students during the School Without Walls programs!
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