Over the past three decades, Bill Acker has established Yap as a world-renowned manta ray dive destination. During this time, the dive community in this region has accumulated a wealth of information about their manta ray population. The goal of this project is to work closely with the dive community of Yap, and throughout the Federated States of Micronesia (FSM), to compile this information into a life history database that will facilitate and improve our understanding of vital components of this population. This newly compiled database combined with new research will provide a strong baseline of information to allow effective monitoring and management of the FSM’s reef-associated manta ray population.
Julie Hartup & Mark Deakos
- Develop a life history database
- Characterise the manta population
- Quantify reproductive success
- Measure growth rates
- Determine age and size at sexual maturity
- Describe habitats used for cleaning and feeding
- Describe feeding patterns
- Contrast Yap’s mantas with other island associated populations
Project Start Date:
Why this is important:
Twenty-seven years ago Yap was one of the first tourist scuba destinations that featured and promoted diving with manta rays. Having observed and photo-identified individuals for nearly three decades, local dive guides have a wealth of information that can advance our long-term understanding of manta ray ecology. Compiling this exceptionally rare and historically rich knowledge base will ultimately provide new insights on a species that we know very little about. Analysis of these findings will also be critical in refining conservation and management policies for this region.
Yap is one of the four states of the Federated States of Micronesia (FSM) and is made up of four continental islands. Located in the Western Pacific Ocean, the thriving coral reefs of these islands not only support a host of marine species, they provide vital cultural and economic benefits to local communities. Over the past three decades, guides have been taking people to dive with the manta rays. During this time, these guides have acquired valuable behavioral and long-term photographic records of the manta rays.
By developing a life history database incorporating long-term historical information and photographic records, we can begin to describe the size, status, and movements of this population, habitat preferences, and quantify the growth and reproductive success of individuals in this population. The database will be further developed to enable the local dive community to easily report new photo-identification and sighting information each day.
Very little work has examined feeding behaviour in manta rays. Recent findings in the Maldives and in Guam suggest that methods of feeding by manta rays will change depending on sites, food source and the number of individual mantas feeding on that source. The location of feeding areas and their proximity to cleaning stations will also be examined.
Evaluating decades of historical data will help us understand long-term trends in island-associated manta ray population. For most researchers studying manta rays in other parts of the world, this historical data is non-existent or difficult to access. New information with systematic reporting by dive guides and guests will greatly improve our understanding of the characteristics of this population and how individual manta rays are using waters around Yap and its neighbouring islands.
- Develop a life history database integrating three decades of observations and photo-identifications.
- Provide the FSM dive industry with the ability to add manta ray sighting information into a user-friendly online database.
- Describe inter-island movements and site fidelity of individual manta rays.
- Determine the reproductive success of females.
- Measure the growth rates of individuals.
- Contrast feeding patterns with those from a Mariana Island (Guam) population.
- Conduct habitat surveys in areas used by manta rays for cleaning and feeding and contrast these with habitats in Guam and Hawaii.
Partners & Sponsors:
Without the generous support and sponsorship we receive we would not be able to achieve our work in the Federated States of Micronesia. We are very grateful to these organisations for their support: