John is looking at the histories that are laid down in the cartilage of shark skeletons throughout their lives, exploring chemical tagging as an alternative means of understanding the details of sharks’ life histories. While we use acoustic, satellite and physical tagging to understand how sharks move and what they do, natural chemical tagging might provide a complementary or alternative method that overcomes some challenges. He will be using spiny dogfish and thorny skates as model species to validate this novel technique.
I am a fish ecologist with broad interests in the life history and population dynamics of fish. I am fascinated by biominerals, the calcified structures that grow incrementally and provide clues to the age of fish and the environments they experience. In my current role as an assistant professor, I am both an educator and a researcher and I mentor undergraduate and graduate students. Mentorship is extremely important to me, as my own mentors shaped the scientist I am today. When I am not in the classroom or lab, you can find me skateboarding, surfing, disc golfing, hiking...
To understand how elements are incorporated into elasmobranch cartilage, to advance knowledge of life history and to support the management and conservation of vulnerable species.
Few methods exist to study the complete life histories of elasmobranchs. Elemental investigations of mineralised chronological cartilage show promise, but laboratory validation is needed to advance this technique in order to promote the conservation of vulnerable species.
The life histories of elasmobranchs are mysterious. Advances in electronic tagging technology have increased our understanding of detailed movement patterns, both horizontally and vertically. This information is essential for defining population structure, assessing connectivity and developing management strategies for conservation. While biotelemetry does provide useful information, it is limited to data post-tagging and only for time frames of months to years. Alternative approaches to studying the life history of elasmobranchs is needed, such as the application of natural chemical tags.
Natural chemical tagging might overcome some of the limitations of electronic tags. First, every individual in a population is naturally marked as they behave normally, so capture and handling is not required. Natural tags include calcified structures that grow incrementally, such as mineralised vertebral cartilage in all elasmobranchs, external spines in dogfish and exterior thorns in skates. All these calcified structures record time and vertebrae uniquely and contain a maternal region that accretes while an embryo is in utero. Thus, natural tags provide a complete life history of an individual.
As natural tags grow, the calcified structures assimilate elements and isotopes from the surrounding water via respiration or through digestive pathways and dietary uptake. Ultimately, dissolved elements in the blood are then transferred to mineralised cartilage as structures grow. Gaining a better understanding of this biochemical process can be achieved using stable isotope ratio spiking experiments. We will also test the usefulness of non-lethal samples (spines and thorns) in model elasmobranch species.
The aim of this project is to confirm the incorporation of elements in the mineralised cartilage of model elasmobranch species, spiny dogfish and thorny skate. The objectives are:
Outside the USA, The Bahamas is the only place where Critically Endangered smalltooth sawfish can reliably be found. Tristan wants to ensure that protection measures in The Bahamas are understood and enforced as far as sawfish are concerned to close the current gap between policy and the people. He’ll be using aerial surveys, sonar and BRUVs, combined with interviews that draw on local knowledge, to identify essential sawfish habitats that need protection. Engaging with the community through workshops and by training students and meeting with government, Tristan intends to advocate for smalltooth sawfish protection throughout The Bahamas’ territorial waters.
Steven and Kevin are using genetic techniques to understand how Caribbean reef shark populations are connected across the extent of their range. Populations of this Endangered shark are in decline generally, but where they are managed and there is effective protection, their numbers are stable. With the integration of the correct information, Steven and Kevin are convinced that we can give Caribbean reef sharks a better shot at recovery and population stabilisation. They will also explore any barriers to connectivity, looking to the future recruitment and recovery of these sharks.
With very little information available about Endangered sicklefin devil rays, their seasonal aggregations at sea mounts in the Azores give Sophie an opportunity to learn more about their lives. She will be collecting satellite-tracking data that show how they move in the Azores’ exclusive economic zone. The information she collects will be used to develop maps of how the rays are using the zone and to identify essential areas that multiple species use. With this information at hand, Sophie hopes her work can contribute to a network of marine protected areas.