Sea Turtle Census addresses issues related to fishing impacts on marine ecosystems by identifying source populations for sea turtles taken incidentally (bycatch) in fisheries around the world, and particularly those close to the USA. To identify which populations are being affected the most (or disproportionately) we need to be able to assign a source population for each individual captured. Some turtle populations have had numbers of breeding turtles decimated in recent decades by fisheries interactions, nesting beach take and egg collection/ poaching. Turtles are not always killed through fisheries interactions, although some species are more vulnerable than others - loggerheads swallow hooks more frequently than leatherbacks that get foul-hooked in the body, neck, or flippers. Individual turtles from nesting populations (or stocks) face threats during migration or at the foraging grounds and it is critical to understand threat levels that these endangered and threatened species experience throughout their life history.
The project's primary research tool is genetic fingerprinting. Using this method, each animal is uniquely identified through a genetic signature using an array of genetic markers (microsatellites and mitochondrial DNA). They currently have baseline data for nesting populations throughout the world for several species and they will use assignment testing and mixed stock analysis to match individuals to their nesting stock source and estimate stock proportions that comprise specific fisheries bycatch. Assignment testing compares an individual’s genetic fingerprint to genetic signatures from all candidate nesting populations. Each incidentally caught turtle is then given a probability of belonging to a particular source stock. For any fishery, the proportion of individuals being caught from vulnerable nesting populations may then be identified.
This project is funded by the Lenfest Ocean Program.