Mackey Violich, a former student from fall 2006, and now a graduate student at the Cape Eleuthera Institute through Florida State University, has been featured on the Cal Bear website. At the University of California Berkeley, Mackey Violich spent 4 years playing division one lacrosse and double majoring in Conservation Resources Studies and Environmental Economics. She is currently working on her masters focusing on the deep-sea ecosystem in the Exuma Sound.
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.
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.
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.
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.
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.
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.
As Hurricane Matthew made contact with the Bahamas in early October, it brought with it many threats of damage and devastation. The Cape Eleuthera Institute (CEI) was extremely fortunate in the sense that Matthew did not hit as hard as expected, but still the storm left its fair share of destruction. Coral reefs offer numerous benefits to ecosystems; one of these being that they can dissipate the power of storm waves generated by hurricanes and therefore lessen the blow of terrestrial damage. However, this absorption of wave energy does not leave the reefs unimpaired.
During large storm systems such as hurricanes, corals are susceptible to fragmentation. Fragmentation is a negative effect in the sense that it can cause some stress to the coral, but on the other hand it can be a positive event because some coral species, such as Elkhorn coral (Acropora palmata) and Staghorn coral (Acropora cervicornis) use fragmentation as a form of asexual reproduction. That is, a new colony can grow from a fragment of the parent colony. Scientists across the Caribbean, including here at CEI, are using this method of growth to create coral nurseries which grow fragments to be outplanted onto damaged reefs.
As CEI continues to focus its research on the endangered Elkhorn coral (Acropora palmata) in the wild, the Coral Team went out to assess the toll Hurricane Matthew had on our local reefs. As expected, there was a decent amount of fragmentation found at Bamboo Point, where there was a large colony of Elkhorn coral with evidence of recent storm damage. Some fragments seen nearby were due to Hurricane Matthew whereas others were older and likely produced by past events. It is CEI’s hope that the newly-formed fragments will proliferate to form new colonies.
In addition to fragmentation, hurricanes have been shown to relieve thermal stress. By mixing the water column and bringing water temperatures down, storms can once again restore favorable thermal conditions and allow coral the chance to recover from bleaching events. As climate change continues and sea surface temperatures rise, coral bleaching events have become more prevalent as the coral’s symbiotic zooxanthellae are expelled. Due to a number of stressors including climate change, overfishing and pollution, coral are increasingly vulnerable. Major storm events are beneficial only once in a while, but if there are too many large storms too often it not only makes the environment uninhabitable for corals, but also can permanently damage reefs that are already existing at the upper limits of their stress tolerance.
As the 2016 hurricane season comes to an end, CEI will continue its monitoring and restoration efforts of Eleuthera’s reefs in the hopes that we can continue to enjoy the many benefits they provide!
It’s been an exciting time for the shark team at the Cape Eleuthera Institute with 2 tagged sharks recaptured over the past few weeks. The team has been conducting frequent long line surveys to collect information about the species, sex and size of the sharks that inhabit the waters around Eleuthera. DNA, blood and muscle samples are also collected from each shark to build up a wealth of biological data which can be used for more in depth studies in the future.
CEI tags all of the sharks that are caught on their longlines with 2 different kinds of tags, a dart tag and cattle tag, which assign an individual tag number to each shark. This not only allows the shark to be easily recognized by the shark team, but also shows other people that these sharks have been caught and sampled by CEI. The tags provide the CEI contact details to allow other research stations or fisherman that may catch the shark to report its location. This recapture data allows the team to analyze distribution behaviors and track the movement of the sharks around Eleuthera.
The most recent recapture was of a female Caribbean reef shark (Carcharhinus perezi) which was caught on the 31st of October, only 300m away from where it was first caught in April 2010. Over the past 6 years this shark has grown by nearly half a meter and now measures a total length of 178cm. A few weeks earlier, on the 12th of October, the team caught a large female nurse shark (Ginglymostoma cirratum) that had not been seen since it was first tagged nearly 8 years ago. This shark had only grown by 3cm over this time but was recaptured nearly 6km away from where it was originally caught and tagged.
Using species-specific size at maturity data, the team can use the total length measurements of these 2 recaptured sharks to estimate that both sharks have recently reached sexual maturity. This is particularly important information when considering the local populations of these sharks as they are now thought to be of reproductive age. These resident sharks will remain around the Cape and contribute to local populations by giving birth to several pups in the mangrove creeks surrounding Eleuthera.
Last year, CEI’s Flats program, along with Georgiana Burruss, CEI Research Assistant, began a three-year study to identify critical bonefish spawning aggregation sites on Eleuthera, The Bahamas. Currently, six spawning aggregation locations have been identified in The Bahamas; one of which is located in South Eleuthera. This study aims to track bonefish populations across Eleuthera to fill this knowledge gap and identify critical habitat for this economically important species.
In year one, the team identified a number of potential bonefish spawning migration corridors in North Eleuthera, South Eleuthera, and along the East coast of Eleuthera. The team deployed 62 VEMCO acoustic receivers to track the movements of 39 tagged fish as they migrated away from known foraging grounds and tidal creeks. Bio-telemetry data indicated potential spawning migration corridors in the North East, South East, and East regions of Eleuthera. In addition, the team was able to track the nighttime movements of spawning aggregations in the South West region of the island. Although, transmitter detections in the North West part of the island were limited, data suggests this may be a result of timing coordinated with spawning-related movements in other regions, indicating that the detections were potentially spawning-related. Interestingly, bonefish tagged in each of the areas were not detected in another region, suggesting these populations are unlikely to mix. Overall, 5 migration corridors have been identified, with data suggesting that there are at least 5 bonefish spawning sites on Eleuthera, although further studies are needed.
Given the success of last year, the bonefish telemetry project officially kicked off its second year of data collection to answer the following questions:
Where are bonefish forming spawning aggregations in the 5 regions of interest on Eleuthera?
How do abiotic factors (season, moon phase, temperature, current, tide, etc.) influence bonefish spawning migrations in South Eleuthera?
What is the energetic cost of spawning migrations?
Two VEMCO positioning arrays were deployed to assess the broad and fine scale spawning migration movements of bonefish in Eleuthera. 42 receivers in the broad scale array were concentrated around zones of interest in each region (identified from last year’s study) to further the understanding of bonefish spawning migrations and staging areas. This increase in coverage combined with manual tracking and visual observations should provide further evidence and confirm our previously identified sites of interests as critical spawning areas. Transmitters will be implanted in 30 bonefish at strategic locations around Eleuthera allowing for the fine scale movements of these fish to be collected. Additionally, these fish will add to the existing 39 bonefish tagged last year to provide unprecedented data on these economically important species. By simultaneously tracking bonefish from several areas of Eleuthera, we can better determine which environmental cues bonefish use to form spawning aggregations, such as moon phase and tides.
At the previously identified spawning aggregation site of interest in South Eleuthera, 31 receivers were placed in an overlapping fine-scale array to track the movements of the bonefish aggregation on an almost continuous basis. This array will allow the team to answer questions related to: how abiotic factors (current, moon phase, seasonality, tide) influence bonefish spawning, how predators interact with the aggregation, understanding the energy expenditure of bonefish when migrating to their spawning site, and potentially the physical act of spawning which is yet to be described. Furthermore, the fine-scale array will fill critical knowledge gaps regarding the diel movements of tagged predatory species, such as great barracuda,Sphyraena barracuda, and blacktip shark, Carcharhinus limbatus. In addition to the basic positional transmitters being deployed, the team will be deploying 20 acoustic transmitters fitted with accelerometer sensors to determine energy expenditure of bonefish during spawning as well as 20 acoustic tags in predatory species to assess predator interactions with the bonefish spawning aggregation. Collectively, findings from this study will be used to develop a management and conservation framework for bonefish and predatory species of surrounding Eleuthera, The Bahamas.
Over the past two weeks the CEI Sea Turtle Research and Conservation team has had the opportunity to join forces with the grade 7 and 8 classes of Deep Creek Middle School (DCMS). The grade 8 students have been studying the Lucayans in both their Art and Social Studies classes. In Social Studies the students were learning about the turtle-catching techniques of the Lucayans. The Lucayan method involved tying string to remoras and once the remora has found and attached itself to a turtle the Lucayans would catch it and bring it onto land. In their art class they took inspiration from the turtles to create a Lucayan style art piece. The grade 8 students met up with the turtle team in Deep Creek and learned how to capture, handle and measure juvenile green sea turtles.
The class broke up into several groups and went out on a small boat to search for turtles within the creek. Once a turtle was spotted one person would keep their eyes on the turtle and point at it while everyone else got their snorkel gear on and ready to go. After the turtle came up to breath a few times swimmers were sent in to chase after the turtle and grab it when it came up to breath.
The following week, the grade 7 class was given a presentation about sea turtles and then came out to Starved Creek to take their turn at chasing turtles as part of the School Without Walls program at DCMS. One of the goals of the School Without Walls program is to get students outside and learn about their environment. The students had the opportunity to hold, measure and chase juvenile green sea turtles as well as learn about the importance and significance of seagrass. The students were very excited to name the turtles tossing out names like Marshmallow, Steve and Diamond!
This partnership between DCMS and the turtle team was a huge success! The students got the opportunity to learn about sea turtles and CEI was able to expand its outreach efforts!
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.
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!
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.
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.
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.
Students, interns, faculty, and staff all exited their designated shelters this morning into the bright Eleuthera sunlight. Island School and Gap Year Students filed out of the Center for Sustainable Development through cheering faculty members, interns are moving back into the grad hall, and our staff are returning to their offices to move everything back into place. Besides a few puddles on floors, our campus fared very well throughout Hurricane Matthew.
Another huge thank you to everybody who sent us good thoughts and checked in with us during the past few days. Our CEI network is strong and we are touched by the concern and compassion that was expressed by our families, friends, alums, and associates.
We will continue to track the weather in the coming days as classes resume, Gap Year students gear up for their triathlon, and researchers get back in the field.