How do we learn about marine food chains when the animals are so difficult to observe? Stable isotope analysis (SIA) shows us what animals eat. Diana will use a new method that combines SIA and amino acids and analyze tissue samples of captive sharks and rays to get a more accurate picture of how this method can be used with wild populations.
If you ask anyone who knew me as a child, they will probably tell you that I talked incessantly about becoming a marine biologist. I was fortunate to grow up in California and spent much of my childhood exploring tidal pools, marvelling at the diversity of species in them and poking at various creatures to see how they would respond. The rocky intertidal zone along the central coast of California is one of the most diverse marine habitats in the world and I had this practically in my backyard. A BSc in marine biology, and later a PhD, made my...
To use feeding records and blood/diet samples from 3 captive elasmobranch species held in public aquariums to generate robust Trophic Enrichment Factors for these species and to compare how TEFs differ between species and animal size. Also, to engage the public about how aquarium animals can benefit ecological research.
While AA-CSIA is poised to strengthen contributions of isotope analysis to elasmobranch conservation more than ever, robust estimates of how amino acids enrich in elasmobranch tissues are lacking. This paucity of information limits the ability of shark researchers to reliably use this powerful new tool on the wide-ranging predators for which traditional SIA is so difficult. Samples from elasmobranchs with known diets are needed to make these estimates. By working with captive animals in public aquaria, we can generate the needed enrichment factors which will be able to be used not only on the vulnerable focal species (C. taurus/C. plumbeus), but on shark and ray species worldwide. Thus, this project focuses on an indirect conservation challenge: improving the tools available to elasmobranch conservation researchers, particularly those focused on trophic and movement ecology. We believe use of this method will grow quickly, necessitating the need for empirical validation now.
Understanding the role elasmobranch predators play in their food webs is critical to conservation and management. Stable isotope analysis (SIA) has become an important tool in studies of trophic interactions, but is hampered by the need for spatiotemporally contemporary baseline samples. For highly mobile predators like large sharks, collecting baseline samples throughout the animal’s range can be impossible – limiting the utility of SIA to study the feeding ecology of these animals.
Many of the limitations of SIA can be circumvented by using compound specific stable isotope analysis of amino acids (AACSIA). AA-CSIA works by separating the constituent amino acids in a tissue sample and analyzing each individually. This new method takes advantage of the fact that “source” amino acids (AAs) do not become 15N-enriched in a consumer’s tissues, while “trophic” AAs become enriched in 15N with each trophic transfer. As a result, source AAs can be used as an internal baseline and by comparing source AAs with trophic AAs, ecologists can calculate the absolute trophic position of a consumer with only a single tissue sample. Making this comparison, however, requires calculation of a Tropic Enrichment Factor (TEF)- the degree to which “trophic” AAs enrich with each transfer. TEF estimates for sharks suffer from extremely low sample sizes and do not exist for rays. Calculating TEFs for a taxa requires sampling animals with known diets, making aquarium-held elasmobranchs ideal focal animals for this research. By gathering samples from multiple elasmobranch species in aquariums around the USA, we will be able to generate robust TEFs with reasonable sample sizes, allowing AA-CSIA to be used to study wild elasmobranchs worldwide.
Did you know that sea turtles can get cancer? Sometimes tumours become so large that they inhibit the turtles swimming, feeding or vision. At the Sea Turtle Hospital, David is using genetics to learn which human anti-cancer drugs can be used to treat turtles.
Australia’s Great Barrier Reef is famous for its coral reef systems, but 1/3 of the reserve consists of largely unknown deep water habitat. These areas are increasingly being fished and deep dwelling sharks and rays are often caught as bycatch. Sam uses stable isotope analysis to better understand these vulnerable species and the threats they face.