MALDIVIAN OCEANIC MANTA PROJECT

Established 2018

The Maldives is home to the worlds largest population of reef manta rays (Mobula alfredi). However more recently, a large population of their larger cousins; the oceanic manta rays has (Mobula birostris) been uncovered. Worryingly, this area is in close proximity to one of the worlds largest oceanic manta fisheries in neighbouring Sri Lanka.

Working as part of the Maldivian Manta Ray Project, this study hopes to learn more about this illusive population and their connectivity throughout the northern Indian Ocean.

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PROJECT OVERVIEW

Sightings data on oceanic manta rays (Mobula birostris) has been collected in the Maldives since the beginning of the Maldivian Manta Ray Project in 2005. However, only in the last couple of years has a large population of this species been identified in the southernmost region of the archipelago attracting more in-depth studies.

By collecting in water photo identification images of the underside (ventral surface) of the manta rays, we have built up an ID database of oceanic mantas in the Maldives. We have identified nearly 700 individuals, most of which have come from Fuvahmulah Atoll. The population appears to be highly transient with individuals spending only short periods of time close to the reef, and rarely being re-sighted. Large aggregations have been recorded in a number of years, but continued observations are needed to confirm the timing and drivers of these aggregations.

Sri Lanka, which is situated 300 kilometres to the north of the Maldives, is home to one of the largest manta and devil ray fisheries in the world. Fisheries research studies conducted by the Manta Trust in Sri Lanka have estimated that thousands of these threatened rays are landed every year across the country. The relatively close distance (1,000 km) between the aggregation sites in the south of the Maldives and the extensive fishery in Sri Lanka is a cause for concern, especially as the Sri Lankan fleet fishes intensively throughout this region of the Indian Ocean. However, at present we have no knowledge of the extent, if any, of the connectivity between these populations.

 
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PROJECT GOALs

To better understand the population dynamics of oceanic manta rays throughout the Maldives Archipelago, and assess the connectivity between the population recorded in the Maldives and the population being fished in neighbouring Sri Lanka. 

Additionally, the project hopes to increase our awarness

 

Main Objectives

To achieve this goal, the Maldives Oceanic Manta Ray Project works to meet the following objectives:

(1) Continue to build upon the photo-ID database of oceanic manta rays in the Maldives.

(2) Tag a selection of oceanic manta rays with satellite tags to determine spatial and temporal movements and habitat use of this species around Maldivian waters.

(3) Collect tissue biopsy samples from a selection of oceanic manta rays in order to conduct stable isotope, fatty acid, and genetic analyses and comparisons with individuals fished in Sri Lanka.

(4) Increase education and awareness within the Maldives of oceanic manta rays and the threats they face throughout the Indian Ocean.

(5) Help advise the relevant government bodies on appropriate measures to be taken to protect oceanic mantas from unsustainable tourism.

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PROJECT LEADER - Simon Hilbourne

The underwater world has always fascinated Simon from a young age. His passion for the ocean stems from watching his parents scuba dive in Sri Lanka whilst he floated above on his body board. Simon took up scuba diving and carried that passion through to work as a scuba instructor for a time in Australia, Cyprus and Honduras.

Enrolling at the University of Southampton in the UK, Simon studied marine biology. His Masters dissertation focused on whale shark seasonality in Mexico. Upon graduating, Simon continued to work with whale sharks, this time in the Philippines, before swapping over to study manta rays in the Maldives. He has been working with the Manta Trust for three years, starting as a volunteer, then taking over as research officer for the MMRP, and is now leading the Maldives Oceanic Manta Ray Project.

Simon is also an avid underwater photographer and loves to try and convey the beauty of the natural world and the conservation issues it faces through his photography.

 
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 Key Achievements

 
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Established a photographic ID database of nearly 700 Mobula birostris individuals in the Maldives.

 

Deployed satellite tags on five individual Mobula alfredi which has provided data on patterns of habitat use as well as feeding and diving behaviour.

 
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Collected tissue biopsy samples for stable isotope analysis to provide information on the dietary preferences of Mobula alfredi in the region so to determine their trophic and movement ecology. Genetic analysis of the samples is also being conducted to identify any connectivity with nearby populations.  

 

Photos from the field

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