Movements and habitat use of satellite-tagged whale sharks off western Madagascar
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Abstract
Whale sharks Rhincodon typus, the world’s largest fish, are routinely sighted off the northwest coast of Madagascar, particularly off the island of Nosy Be. Dedicated whale shark tourism has been developing in the area since 2011. During our first dedicated survey, from September-December 2016, we photo-identified 85 individual whale sharks, ranging from 3.5–8 m in total length (all juveniles). None had been previously identified from other known whale shark aggregations. We tagged eight sharks with tethered SPOT5 tags in October 2016, with tracking durations of 9–199 days. Kernel density plots showed that the main activity hotspot for tagged sharks was around the Nosy Be area. Three individuals were resighted back at Nosy Be in late 2017, after having lost their tags. A secondary hotspot was identified off Pointe d’Analalava, 180 km southeast of Nosy Be. Five sharks swam off the shelf into the northeastern Mozambique Channel, between Madagascar and Mayotte, and one of these continued to near the Comoros islands. Two sharks swam to southern Madagascar, with minimum track distances of 3414 km and 4275 km. The species is presently unprotected in Madagascar, although a small proportion of the high-use area we identified in this study is encompassed within two marine protected areas adjacent to Nosy Be. Whale sharks are globally endangered, and valuable to the local economy, so there is a clear rationale to identify and mitigate impacts on the sharks within the two hotspots identified here.
Cite this as
2018. Movements and habitat use of satellite-tagged whale sharks off western Madagascar. PeerJ Preprints 6:e3508v1 https://doi.org/10.7287/peerj.preprints.3508v1Author comment
This is a preprint submission to PeerJ Preprints. It will shortly be submitted for publication with Endangered Species Research.
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Additional Information
Competing Interests
Stella Diamant is the Project Leader at the Madagascar Whale Shark Project. Christoph A Rohner and Simon J Pierce are both Principal Scientists at the Marine Megafauna Foundation. Jeremy J Kiszka is a Research Assistant Professor at Florida International University. Arthur Guillemain d’Echon and Tanguy Guillemain d’Echon own Les Baleines Rand’eau in Nosy Be, Madagascar. Elina Sourisseau is the Coordinator of Mada Megafauna.
Author Contributions
Stella Diamant conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Christoph A Rohner conceived and designed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Jeremy J Kiszka conceived and designed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, reviewed drafts of the paper.
Arthur Guillemain d’Echon conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, reviewed drafts of the paper.
Tanguy Guillemain d’Echon conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, reviewed drafts of the paper.
Elina Sourisseau conceived and designed the experiments, contributed reagents/materials/analysis tools, reviewed drafts of the paper.
Simon J Pierce conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, reviewed drafts of the paper.
Animal Ethics
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
Authorisation to deploy satellite tags on whale sharks was delivered by the Centre National de Recherches Océanographiques in July 2016 under the number N°16-12-CNRO-N.
Field Study Permissions
The following information was supplied relating to field study approvals (i.e., approving body and any reference numbers):
Authorisation to deploy satellite tags on whale sharks was delivered by the Centre National de Recherches Océanographiques in July 2016 under the number N°16-12-CNRO-N.
Data Deposition
The following information was supplied regarding data availability:
Wildbook for Whale Sharks photo-identification database.
Funding
This study was supported by donations to SJP and CAR from two private trusts, Aqua-Firma, Shark Foundation, and Waterlust. Field costs for SD were covered by the PADI Foundation, and camera equipment was donated by IdeaWild. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.