To be able to develop effective protection strategies for reef manta rays throughout the world, it is essential that we understand the functioning of a natural marine ecosystem. Under overwhelming human pressures such as tourism, large-scale fisheries and habitat degrading activities which may distort natural ecosystem functioning, few such marine environments exist making the establishment of a natural baseline challenging.
The Chagos Archipelago British Indian Ocean Territory (BIOT) comprises a group of seven atolls, located 500 km south of the Maldives in the Indian Ocean. The region has been uninhabited since 1970 (except for military personnel on Diego Garcia Atoll), and in April 2010, the British government established the entire archipelago as a Marine Protected Area (MPA). Spanning an area of 640,000 km2, it is the second largest MPA in the world. In the absence of human pressures, the area is host to one of the world’s most pristine marine environments where ecosystem functioning is in a near-natural state. This makes the little know population of reef manta ray in the region unique as they are protected from some of the most threatening human stressors.
As a remote, virtually uninhabited and strictly protected location it is not possible to have a local field base, so since the establishment of the Manta Trust’s Chagos Manta Ray Project, research has been conducted in carefully planned stages. Various successful techniques have been employed including photographic identification and satellite tagging to gather data on the population’s size, demographics, movement ecology and feeding behaviour.
Recent tagging studies have delivered great news; the tagged manta rays never left the safe haven of the MPA. The study also identified an aggregation hotspot at Egmont Atoll. The project now aims to identify the biological and physical drivers of these aggregations in the absence of human pressures to assist in identifying crucial reef manta ray habitats throughout the world.
The Chagos Manta Ray project will continue to develop their photo identification database of all encountered reef manta rays so to establish population size and demographics and to gather information on the behaviour and physical condition of the individuals. Through the integration of acoustic tag data, in situ environmental measurements, stable isotope and genetic analysis the project also aims to elucidate their movement patterns, degree of connectivity between populations, dietary preferences and trophodynamics which will improve ecological understanding of the species. It will also assist in identifying the environmental influences of their movement behaviour. Furthermore, understanding the environmental drivers of their movement ecology in an environment that is almost completely devoid on anthropogenic stressors will assist in identifying regions that are conservation concern throughout the world.
To achieve their goals, Chagos Manta Ray Project works to meet the following objectives:
1. Continue to build the photo-identification database of the reef manta rays to establish the overall population size, demographics and fecundity.
2. Clarify the dynamic association between manta rays and the physical environment with a particular focus on identified hotspots using acoustic tags and environmental measurements to intensively assess the drivers of visitation patterns and behaviour.
3. Collect tissue samples for stable isotope and genetic analysis to elucidate their movement patterns, degree of connectivity between populations, dietary preferences and trophodynamics which will improve ecological understanding of the species
4. Assess the effectiveness of the MPA through long term monitoring of the species using the above methods.
PROJECT LEADER - JOANNA HARRIS
Joanna began snorkelling at just three years old and fell in love with the ocean. Spending every moment possible in the water earnt her the childhood nick name ‘water baby’. After spending many years travelling the world to snorkel and SCUBA dive she naturally developed a passion for marine conservation. Joanna studied for a degree in marine conservation at Cornwall College, Newquay where she became an advocate for the urgent need for reef manta ray protection and began volunteering for the Manta Trust. She then progressed to an honour’s degree in marine zoology where her research focused on the movement ecology of the reef manta ray in the Maldives. Joanna’s passion for manta ray conservation and research then led her to a master’s in marine science where she began to study the reef manta ray of the Chagos Archipelago; British Indian Ocean Territory (BIOT). Now embarking on a PhD at the University of Plymouth, Joanna will be continuing this work. As one of the most pristine marine environments on Earth, Joanna aims to understand the dynamic relationship between reef manta rays and the natural environment which will assist in identifying crucial habitats and conservation requirement throughout the world.
Established a photographic ID database which, so far, has documented more than 125 of the regions Mobula alfredi population.
Deployed satellite tags on five individual Mobula alfredi which has provided data on patterns of habitat use as well as feeding and diving behaviour.
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
Sponsors & Partners
University of Plymouth, UK
The Bertarelli Foundation
Garfield Weston Foundation
Zoological Society of London