Global elasmobranch declines are well documented, yet rays have received far less attention than sharks despite sharing similar life histories that make them susceptible to extrinsic pressure and potentially vulnerable to population declines through overfishing or habitat degradation. In tropical marine environments, rays make up a significant portion of coastal fish biomass and typically characterise community composition in nearshore ecosystems, yet few data are available on the functional role and life history characteristics of rays in these environments. Demersal species, such as stingrays have been shown to regulate biological communities through their predation behaviours, but also impact soft sediment environments chemically and physically, leading to the notion that they are ecosystem engineers and therefore could be considered critical agents of ecosystem function. The International Union for the Conservation of Nature (IUCN) considers many Caribbean species data-deficient, despite their functional significance and increasing economic value as a tourism commodity throughout the region.
The Bahamas is a unique environment within which to investigate these animals, as they are largely understudied despite being ubiquitous throughout the islands. Additionally, the dynamic and fragmented nature of the Bahamian archipelago, further provides critical need in assessing these species on account of rapid urbanisation and human incursion to coastal ecosystems. It is for these reasons, that in January 2015, the Batoid Research Group began in earnest at the Cape Eleuthera Institute. The mission of this program is to promote the ecological significance and conservation value of coastal and nearshore ecosystems by highlighting various aspects of stingray biology, ecology and life-history.
Some of our current projects include:
Next generation sequencing in the Caribbean whiptail stingray- The Caribbean whiptail stingray Styracura schmardae is not formerly recognised from The Bahamas, except for a single published sighting in 1969. This research group has been unraveling the mysteries surrounding this elusive ray and has been conducted surveys through Eleuthera, Great Exuma and the entire Exuma Cays island chain. Specifically this project has collected tissue from almost 100 individuals across sixteen spatially distinct locations to assess genetic connectivity across restricted temporal scales, i.e. parentage and sibling relationships, to assess dispersal potential. We have also published the first range extension of this species, updating its contemporary distribution.
Population genetics in southern stingrays- Dasyatis americana from the central and northern Bahamas. This investigation will show if the observed female residency in one location is random individual preference or if female southern stingrays are building resident (sub) populations that might only be connected through transient males. Information derived from this research will allow us to further understand how gene flow and connectivity within this species is proliferated among sites, and may uncover migratory pathways critical for the propagation of these rays.
Stable isotope assessment of two species– the southern and Caribbean whiptail stingray. Specifically this work is a) validating isotopic signatures with stomach content analysis, b) assessing the different retention times of carbon13 and nitrogen15 in a range of tissue types including muscle, blood, mucus, spine and skin, c) manipulating diet in captive rays to measure turn over rate of isotopic signatures, d) assessing ontogenetic diet shift in Caribbean whiptail stingrays and relating this to size mediated habitat association and e) determining trophic resource partitioning between two species from multiple locations.
Temperature preference and thermal niche in southern stingrays- This project aimed to uncover temperature as the abiotic master factor in determining the spatial distribution of stingrays within several distinct subpopulations. This work has increased our understanding of how environmental variables influence subpopulation structure and further showed microhabitat occupancy by rays based on environmental thermoscapes.
Prey discrimination in yellow rays Urobatis jamaicensis- This project is an experimental approach in assessing electrosensory mediated prey discrimination among yellow rays. Having completed a detailed dietary study of this species, we are aiming to determine the extent to which prey location and discrimination is mediated through electrosensory ability alone. This research aims to address potential disruption in electrosensitive fishes as a result of offshore renewable energy developments.
Previous studies have focused on:
Comparative feeding assessment in yellow rays- This research has been able to describe the diets from 120 yellow rays across three distinct sites, and then through invertebrate surveys from the same sites, was able to determine foraging strategy and prey preference. This information will allow us insight into the roles of these small rays in structuring invertebrate communities, as well as increasing our understanding of invertebrate fauna in Eleuthera.
Assessing diel activity patterns in southern stingrays- The use of tri-axial accelerometers to measure acceleration is a well-established method of determining activity and movement patterns in marine organisms, yet has never before been used in the assessment of southern stingray motion budgets. The current study presents a novel technique for collecting activity data on southern rays using emerging technologies.
Collaboration & Support
Our research is in collaboration and partnership with the College of Life and Environmental Sciences Exeter University, The Florida Fish and Wildlife Conservation Commission, School of Marine and Atmospheric Sciences Stonybrook University, Faculty of Biological Sciences and Biotechnology Ruhr University Bochum, Newcastle University, The Rufford Foundation, Idea Wild and the Shedd Aquarium.