Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea
KAUST DepartmentBiological and Environmental Sciences and Engineering (BESE) Division
Red Sea Research Center (RSRC)
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AbstractBackground Despite being frequently landed in fish markets along the Saudi Arabian Red Sea coast, information regarding fundamental biology of the Scalloped hammerhead shark (Sphyrna lewini) in this region is scarce. Satellite telemetry studies can generate important data on life history, describe critical habitats, and ultimately redefine management strategies for sharks. To better understand the horizontal and vertical habitat use of S. lewini in the Red Sea and to aid with potential future development of zoning and management plans for key habitats, we deployed a pop-up satellite archival transmitting tag to track a single female specimen (240 cm total length) for a tracking period of 182 days. Results The tag was physically recovered after a deployment period of 6 months, thus providing the complete archived dataset of more than one million depth and temperature records. Based on a reconstructed, most probable track, the shark travelled a circular distance of approximately 1000 km from the central Saudi Arabian Red Sea southeastward into Sudanese waters, returning to the tagging location toward the end of the tracking period. Mesopelagic excursions to depths between 650 and 971 m occurred on 174 of the 182 days of the tracking period. Intervals between such excursions were characterized by constant oscillatory diving in the upper 100 m of the water column. Conclusions This study provides evidence that mesopelagic habitats might be more commonly used by S. lewini than previously suggested. We identified deep diving behavior throughout the 24-h cycle over the entire 6-month tracking period. In addition to expected nightly vertical habitat use, the shark exhibited frequent mesopelagic excursions during daytime. Deep diving throughout the diel cycle has not been reported before and, while dive functionality remains unconfirmed, our study suggests that mesopelagic excursions may represent foraging events within and below deep scattering layers. Additional research aimed at resolving potential ecological, physiological and behavioral mechanisms underpinning vertical movement patterns of S. lewini will help to determine if the single individual reported here is representative of S. lewini populations in the Red Sea.
CitationSpaet JLY, Lam CH, Braun CD, Berumen ML (2017) Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea. Animal Biotelemetry 5. Available: http://dx.doi.org/10.1186/s40317-017-0135-x.
SponsorsWe would like to thank Abdullh A. Aljahdali, Esam S. Aljahdali, Gazzi J. Aljahdai, Abdulmohsen H. Aljahdali and the King Abdullah University of Science and Technology Coastal and Marine Resources Core Lab for facilitating the fieldwork of this study; Pedro R. de la Torre and Lloyd Smith for assistance with tag retrieval and Gregory B. Skomal for facilitating the tag data transfer. We are grateful to Stein Kaartvedt, Burton Jones, and Anders Røstad for helpful discussions of the data. We would also like to thank Austin Gallagher and one anonymous reviewer for helpful feedback on the manuscript. Funding for the research was provided by the King Abdullah University of Science and Technology (baseline research funds to MLB).
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