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From DNA to MPA: developing genetic techniques to improve the management and protection of threatened manta ray populations
Accurate information on population size and structure is necessary in order to understand the conservation requirements of a species, develop management strategies, and to assess and monitor population health over time. My PhD project focuses on fine-scale population genetics of reef manta rays, Manta alfredi, in two separate locations – Southern Mozambique and Raja Ampat, Indonesia. I will use genetic markers to estimate effective population size, investigate spatial connectivity and generational relatedness in order to gain insight into the structure of these populations. I am also interested in the relatedness of individuals sighted in regular social groupings, as well as the occurrence and expression of melanism (black colour morphs) in my two focal populations.
Manta rays are iconic marine animals and focal species for marine tourism industries across the globe. Despite their iconic status, localised population declines have been documented in several regions, with some reductions as high as 86% of baseline numbers. Global manta ray populations are under increasing pressure from target and by-catch fisheries, driven by the demand for their branchial filter plates, which are highly prized for use in Chinese health tonics. Due to their conservative life history traits manta rays are considered highly unsustainable as a fishery resource as populations have a reduced ability to recover numbers once depleted. Accordingly, both Manta birostris and Manta alfredi are classified as ‘vulnerable to extinction’ on the IUCN Red List of Threatened Species and the development of effective management and conservation strategies is of critical importance to adequately protect global populations.
Manta ray research is still in its infancy and substantially more information is needed to determine the best strategies to guide effective management initiatives on a regional and global scale. The development of such programs requires accurate information on population size and structure to assess population health and provide baseline data for long-term monitoring. Such ecological abundance estimates can take years to complete, yet declining populations may require rapid assessments in order to develop effective management and conservation strategies. Population genetic assessments can provide this information in a relatively short timeframe compared to long-term photo-ID studies.
My research will complement long-term photo-ID, movement and feeding ecology studies previously conducted in Mozambique and Indonesia, providing valuable insight into the size and structure of focal populations that can be used to improve regional management and protection. It will also facilitate the refinement of genetic techniques for application on a global scale, for use in rapid, yet efficient population assessments when time does not permit for long-term photo-ID studies