New insights into the trophic ecology of young white sharks (Carcharodon carcharias) in Baja California
New insights into the trophic ecology of young white sharks (Carcharodon carcharias) in waters off the Baja California Peninsula, Mexico
Elena Tamburin, Fernando R. Elorriaga‑Verplancken, Colombo Estupiñan‑Montaño, Daniel J. Madigan, Alberto Sánchez‑González, Mauricio Hoyos Padilla, Michelle Wcisel, Felipe Galván‑Magaña
Marine Biology 167, 55 (2020)
DOI: https://doi.org/10.1007/s00227-020-3660-8
Abstract
White sharks (Carcharodon carcharias) are described as generalist predators, with a demonstrated ontogenetic dietary shift which occurs between subadult and adult life stages. Trophic ecology studies on white shark have been focused mainly on large and mature individuals, necessitating studies of young white shark trophic ecology to better understand their resource use. This study provides new insights into young white shark diet in the North eastern Pacific Ocean using stable isotope analysis in muscle tissues. We analyzed δ13C and δ15N values of young white shark muscle (n = 21) from Sebastián Vizcaino Bay (SBV) during 2015–2018. We found changes in prey composition across early [neonates, young-of-the-years (YOYs), juveniles] white shark life stages, with significant changes in isotopic composition throughout early ontogeny. Mixing model results indicate a high use of coastal areas for foraging, mainly for juvenile stages and the substantial contribution of pelagic preys (e.g., S. japonicus, Prionotus spp., Cynoscion spp., S. sagax, etc.) in YOYs, white shark diet also indicates an important role of offshore foraging. This change in isotopic composition likely represents the shift from the embryo’s typical maternally derived isotopic signature, incorporated in offshore foraging regions, to the postpartum isotopic composition incorporated by foraging neonates in inshore nursery habitats. This study provides relevant information regarding young white shark feeding preferences, reinforces the importance of coastal areas as critical habitat for the development and the successful foraging of this species, and also provides indirect insights on the feeding habits of the adult female of white sharks, which constitutes a baseline for further research.
Keywords: Ontogenic shift, life stages, nursery areas