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.
On Wednesday, August 31, 2016, the CEI Shark Research and Conservation Team caught and sampled a huge 258 cm male lemon shark (Negaprion brevirostris). This thrilling capture was made while conducting a longline survey off of Cape Eleuthera, Bahamas to establish a dataset about the abundance and size of different coastal shark species in south Eleuthera. Although a wide variety of sharks can be found around the Bahamas, and there are many known lemon shark nurseries, mature lemon sharks are not commonly seen near south Eleuthera. The information collected from this rare catch can be used to trace the lineage of lemon shark populations found throughout the Bahamas, which can ultimately help influence future shark conservation and management initiatives.
Lemon sharks are a large species of coastal shark that can reach up to 3.5 m in length. They can be identified by their pale brown or olive coloring, and their two equally sized dorsal fins. Lemon sharks are listed as Near Threatened and their position at the top of the food chain makes them a valuable species for the local ecosystems. However, there is a limited amount of data on these adult sharks in this area which makes this catch all the more exciting. The Bimini Biological Field Station fills this knowledge gap by reconstructing adult male genetic information using the samples from the more abundant juveniles. Now we can include the data collected from this individual to create a more complete understanding of the local lemon shark population.
During the workup procedure, the lemon shark was measured to obtain information about its size, age, and sex, which can then be added to the data collected by CEI to show the dynamics of the local populations of sharks. The size of the shark was recorded by taking three specific measurements of its body. The team also collected a tissue sample, which will be used to build up a long term genetic record of the shark populations around Eleuthera. After all measurements and samples were collected, the lemon shark was tagged using a dart tag and a dorsal tag. These tags are used for identification purposes, allowing the research team to recognize a recapture. Following the workup procedure, the lemon shark was released in great condition and everybody was left in awe as it swam away.
Globally, sharks are among the most threatened group of species, facing some of the greatest population declines in modern history. This is exacerbated by conservative life history characteristics such as slow growth rates, late maturity ages and low number of offspring, which in turn increase their vulnerability to extinction. Turtles also exhibit similar life history characteristics, therefore assessing their importance as a food source and the significance predation has on their population can help us to further conservation efforts. This summer, Newcastle University student Massimo Casali in collaboration with the Cape Eleuthera Institute’s Shark Research and Conservation Program has been conducting a study to elucidate the importance of habitat complexity and coastal shark species on turtle abundance in different creek systems. The Bahamas offers unique opportunities to study turtles and sharks on account of a total ban being enforced since 2009 and 2011 respectively, and so this project will take advantage of the relatively untouched environment of south Eleuthera, The Bahamas.
Through the use of experimental longlines, sharks are caught in close proximity to creek systems before being sampled, including the taking of morphometric data (measurements), tissue harvest for stable isotope analysis and tagging, allowing for mark-recapture assessment. So far the team has caught a total of 21 sharks represented by 5 species; nurse shark (Ginglymostoma cirratum), Caribbean reef shark (Carcharhinus perezi), blacknose shark (C. acronotus), blacktip reef shark (C. limbatus) and tiger shark (Galeocerdo cuvier). This research has also included a range of educational programmes and Island School classes enabling us to reach a broad range of budding young shark scientists.
Overall, the research objectives of this study will form the basis for Massimo’s undergraduate research dissertation, that will specifically address the relationships between sea turtle and shark abundance in these biologically diverse ecosystems, considered fragile due to human induced disturbances. This will further allow conservation frameworks that will allow the management of sensitive coastal ecosystems throughout The Bahamas.
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.
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.
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.
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.
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.
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).
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.
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.
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 .
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!
Last week, the Stingray Research Group, headed by Dr. Owen O’Shea, took 15 of our Bahamian staff members out to The Schooner Cays– a location the majority of staff have never visited despite gracing the views from office windows all over campus. The goal was for the team to experience and learn the scientific objectives of this research project Two groups of staff were organised into morning and afternoon trips, along with other ray team members. First, there was safety briefings and capture methodologies discussed in the boathouse, along with the objectives and conservation ambitions of this research, before heading out on the water to find rays.
The morning group, featuring kitchen manager Sophia Louis, guest services employee Corey Lightborne, and Bio-diesel engineer Sammy Dorcent, saw five stingrays caught in just 3 hours, including three new individuals, and the retrieval of one of our data loggers. The team was enthused and excited to be part of this research, and preconceptions regarding these gentle animals were challenged, with every member participating in either catching or working up animals.
The afternoon session saw a slightly tighter schedule (largely due to inclement weather), and included head of facilities Oscar Knowles, most of the accounts team, and campus mechanic Valentino Hall, who helped catch two additional rays. We were also able to deploy a data logger and, like the morning team, we travelled back to Cape Eleuthera to the sound of joyous discussion on how valuable the experience was. Requests for further expeditions have been made, and certainly the Stingray Research Group aims to make another trip before Christmas, for those staff unable to attend this one.
Stingrays are among a group of animals poorly understood and often feared among Bahamians, and so sharing this work and allowing up close and personal interactions with these rays has dispelled myths and changed perceptions, certainly among those staff who attended.
The main objective of the project is to tag oceanic whitetips in The Bahamas, a shark sanctuary, and to track their movements. This can be compared to areas of protection vs. potential threats. This information can then be used to influence policy and management on a national level.