Spatial connectivity of reef manta rays across the Raja Ampat archipelago, Indonesia

Area of Science:

• Marine Biology
• Conservation Science
• Population Genetics

Background:

• The reef manta ray (Mobula alfredi) is protected across Indonesia's Raja Ampat archipelago.
• Current management assumes a single, homogeneous population, lacking evidence on spatial connectivity.
• Understanding population structure is crucial for effective conservation of this species.

Purpose of the Study:

• To investigate the spatial connectivity and population structure of Mobula alfredi within Raja Ampat.
• To identify critical habitats and movement corridors for reef manta rays.
• To inform the management of Mobula alfredi populations in Raja Ampat.

Main Methods:

• Acoustic telemetry using 34 receivers deployed across Raja Ampat (February 2016 - September 2021).
• Tracking of 72 tagged subadult and adult Mobula alfredi.
• Network analysis and community detection algorithms to analyze movement patterns.

Main Results:

• 1094 Mobula alfredi movements were recorded, primarily showing local movements within regions.
• Limited long-distance movements were observed between regional acoustic receiver arrays.
• Network analysis identified key 'hub' sites and revealed three distinct population clusters.

Conclusions:

• Evidence suggests Mobula alfredi in Raja Ampat form a metapopulation with three subpopulations.
• Eagle Rock is identified as a critical node in the manta ray movement network.
• Urgent inclusion of Eagle Rock into the Raja Ampat marine protected area network is recommended.