Thesis: Movement patterns, trophic role and ecology of the reef manta (Manta alfredi) in the D'Arros Marine Protected Area
My PhD will examine the movement patterns, predator-prey relationships, feeding ecology and demography of reef manta rays (Manta alfredi) within the D’Arros and St Joseph Atoll Marine Protected Area (MPA). This work will build on the existing networks of sonar receiver stations and tagging efforts in order to build a 3-dimensional picture of the spatial and temporal patterns in movements of manta rays in relation to their predators, food and the boundaries of the MPA. The generality of the patterns recorded at D’Arros will then be examined by comparison with other data sets from localities across the Indian Ocean to both collate photo-identification libraries of individual mantas and search for evidence of long-distance (100-1000 km) migrations.
Why my research is important
Understanding how reef mantas are utilising the D’Arros MPA is very important to ensuring the continued survival of this species. Manta ray populations have suffered drastic declines across the past 75 years, with numbers decreasing globally by around 30% and losses of up to 80% being witnessed in some areas. As a species known to exhibit slow life history traits, reef mantas are unable to cope with the high rates of harvest and/or by catch to which they are currently subjected and this has resulted in their listing as "Vulnerable" by the International Union for the Conservation of Nature (IUCN).
Reef manta population declines are driven largely by demand from the Chinese traditional medicine market for manta gill rakers, as well as for food in smaller fishing villages, and by-catch in both fishing nets and on long lines. As majority of the fisheries around the world targeting these animals are of an artisanal, small-scale and by-catch nature, it is difficult to decrease the mortality of mantas rays using traditional approaches to fisheries management. It is in these circumstances that we turn to MPA’s as a method to manage and conserve reef manta ray populations. The overarching aim of my PhD is to investigate key aspects of reef manta biology within the D’Arros Island MPA to not only further our understanding of the movement and behavioural ecology of this species, but to assess if the MPA in this region is benefiting current conservation efforts for the reef manta and determine how future MPAs may be better designed in order to more effectively protect these charismatic elasmobranchs.