Remote hideaways: first insights into the population sizes, habitat use and residency of manta rays at aggregation areas in Seychelles

February 2024

Lauren R. Peel, Mark G. Meekan, Ryan Daly, Clare A. Keating, Shaun P. Collin, Josep Nogués & Guy M. W. Stevens 

Keywords: Mobulid • Elasmobranch • Abundance • Conservation • Lagoon • Coral atolls • Mobula alfredi • M. birostris

Summary: This study focused on understanding population sizes, residency patterns, and habitat use of oceanic and reef manta rays in Seychelles. Through photo-identification and remote underwater camera systems from 2006 to 2018, they found infrequent sightings of oceanic manta rays, indicating possible aggregation areas beyond the study's scope. Reef manta rays however, showed frequent sightings at specific locations, with equal representation of males and females. They noted a crepuscular foraging strategy and suggested that marine protected areas in Seychelles could benefit reef manta ray conservation with proper regulations and monitoring.

Abstract

“Understanding the aggregation and habitat use patterns of a species can aid the formulation and improved design of management strategies aiming to conserve vulnerable populations. We used photo-identification techniques and a novel remote underwater camera system to examine the population sizes, patterns of residency and habitat use of oceanic (Mobula birostris) and reef (Mobula alfredi) manta rays in Seychelles (5.42°S; 53.30°E) between July 2006 and December 2018. Sightings of M. birostris were infrequent (n = 5), suggesting that if aggregation areas for this species exist, they occur outside of the boundary of our study. A total of 236 individual M. alfredi were identified across all surveys, 66.5% of which were sighted at D’Arros Island (Amirante Group) and 22.5% at St. François Atoll (Alphonse Group). Males and females were evenly represented within the identified population. M. alfredi visited a cleaning station at D’Arros Island less frequently during dawn and dusk than at midday, likely due to the adoption of a crepuscular foraging strategy. The remote and isolated nature of the Amirante and Alphonse Group aggregation areas, coupled with the lack of a targeted mobulid fishery in Seychelles, suggests that with appropriate regulations and monitoring, the marine protected areas gazetted within these two groups will benefit the conservation of M. alfredi in Seychelles”

Infographics

Author Affiliations

  • School of Biological Sciences, The University of Western Australia

  • The Australian Institute of Marine Science

  • Save Our Seas Foundation—D’Arros Research Centre

  • The Manta Trust

  • The Oceans Institute, University of Western Australia

  • Oceanographic Research Institute, South African Association for Marine Biological Research

  • South African Institute for Aquatic Biodiversity (SAIAB)

  • School of Agriculture, Biomedicine and Environment, La Trobe University

  • Island Conservation Society

  • Island Biodiversity and Conservation (IBC) Centre

  • University of Seychelles

Funded by

  • CAUL and its Member Institutions

  • Save Our Seas Foundation

  • The Manta Trust

  • Australian Institute of Marine Science

  • SOSF-D’Arros Research Centre

  • Island Conservation Society (ICS)

  • The Alphonse Foundation

  • The University of Western Australia

  • Islands Development Company

  • Blue Safari Seychelles

  • The University of Western Australia Postgraduate Student’s Association