- Population Size and Structure
- Stable Isotope Analysis
- Population Genetics
- Determine Habitat Utilisation
- Foraging Behviour
- MPA Effectiveness
Project Start Date:
Like many of the other Manta Trust projects, a photo identification database of all encountered reef manta rays (Manta alfredi) will be created, documenting population size, information on sex, reproduction, age class, observed behaviour and physical condition of the individuals, allowing us insight into the demographics and fecundity of the population. Tissue samples will be taken from a sub-sample of the populations and will be analysed to investigate the genetic relatedness of the Chagos population with other manta populations throughout the Indian Ocean. Tissue samples will also be taken for use in stable isotope analysis. Reef manta rays will be tagged with acoustic and GPS satellite tags to provide a wealth of information on the broad and fine-scale movements of the mantas spatially and temporally. This data will then be used to determine the key areas of habitat use for this manta population within one of the world’s largest marine protected areas (MPA).
To conduct this pioneering research in the Chagos Archipelago and to achieve all of these goals, the Manta Trust will be working with partner organisations; the Chagos Conservation Trust and the Zoological Society of London.
Why this is important:
The Chagos Archipelago is the world’s second largest Marine Protected Area (MPA) and by extracting information on manta ray movements we will be able to asses the extent to which manta rays remain inside the MPA boundaries and as such test the effectiveness of the established MPA. The Manta Trust also has a sister project in Sri Lanka whose project staff collect tissue samples and data on the mantas which are landed at the fish markets in this country. It is known that Sri Lankan fishermen venture into the Chagos archipelago to carry out illegal fishing. By collecting and comparing genetic samples and photo-IDs of the manta rays encountered at both locations, we hope to monitor any potential illegal fishing of the Chagos mantas which may be occurring.
The Chagos Archipelago comprises a group of seven atolls, located 500km south of the Maldives in the Indian Ocean, officially part of the British Indian Ocean Territory. The archipelago has been uninhabited since 1970 (except for military personnel on Diego Garcia Atoll) when the UK allowed the USA to build a military base on the largest of the Chagos islands. In April 2010, the British government established the entire archipelago as the world’s largest Marine Protected Area spanning an area of 640,000 km2 (In 2012 a new MPA created in the South Pacific overtook Chagos as the world’s largest MPA). Due to the lack of human presence and human activity throughout the archipelago, the Chagos MPA contains one of the healthiest reef systems and unpolluted waters in the entire world.
This lack of human touch offers a fantastic opportunity to study manta rays in a protected and pristine environment without heavy anthropogenic impacts such as tourism and large-scale fishing pressures. The large amount of shallow coral atoll habitat contained within the archipelago is ideal for reef mantas. Our tagging studies allow us to track the mantas movements and foraging behaviour as they travel around these reefs and atolls, between feeding and cleaning sites. Our genetic sampling will be used in a global population genetics study which is important in assessing if and how global populations of manta rays are linked and how the species dispersed.
- Create a photo-identification database of the reef manta rays to study the overall population demographics, size and fecundity.
- Tag reef mantas with acoustic and satellite tags to gain insight into their foraging strategies and movements within and between the reef systems.
- Collect tissue samples from both species of manta rays for genetic and stable isotope analysis in order to assist these large-scale initiatives being undertaken by other Manta Trust projects.
- Use all of the above to assess the effectiveness of the Chagos MPA at protecting both species of manta rays.
Partners & Sponsors:
Without the support of our partners and the generous sponsorship received we would not be able to achieve our work in the Chagos Archipelago (BIOT). We are therefore very grateful to these organisations: