New insights into the migration patterns of the scalloped hammerhead shark Sphyrna lewini
New insights into the migration patterns of the scalloped hammerhead shark Sphyrna lewini based on vertebral microchemistry
Claire Coiraton, Felipe Amezcua, James T. Ketchum
Marine Biology 167, 58 (2020)
DOI: https://doi.org/10.1007/s00227-020-3668-0
Abstract
The scalloped hammerhead shark Sphyrna lewini is a migratory species that exhibits complex patterns of spatial organization associated with the use of both coastal and oceanic habitats. Information about its movements and habitat use is fragmentary and recent study showed that elemental signatures deposited in its vertebrae served as reliable site-specific markers. Age-related movements of S. lewini in the Mexican Pacific were examined using vertebral microchemistry. Vertebrae were obtained from 48 sharks captured in 2016. Elemental signatures were quantified using laser ablation-inductively coupled plasma mass spectrometry. Spatial variability of the vertebral edge elemental signatures was first assessed to verify that microchemistry could distinguish among sharks based on recent habitat use before inferences on environmental histories could be made. Age-related movements were then assessed by quantifying changes in the Sr:Ca, Ba:Ca, Sr:Ba and Pb:Caratios along vertebral transects encompassing complete life histories. Analysis of elemental profiles suggested that S. lewini exhibits movements that are likely more plastic than previously assumed, with a stronger association to coastal habitats than expected. Females used highly variable habitats over their lifetime and males alternated between two migratory patterns, coastal or pelagic, as they either remained nearshore for their entire life or migrated offshore to later return to coastal habitats. Migratory contingents or partial migration might be a strategy of S. lewini to reduce vulnerability to stressors among regions. Scalloped hammerhead persistence in the Mexican Pacific, despite being heavily fished, may be linked to behavioral plasticity of movement rather than its life history characteristics.
Keywords: Migration, Vertebral Microchemistry, Scalloped Hammerhead