Trophic resources and mercury exposure of two silvertip shark populations in the northeast Pacific Ocean

Type Article
Date 2020-08
Language English
Author(s) Le Croizier Gaël1, 2, Lorrain Anne2, Schaal Gauthier2, Ketchum James3, 4, Hoyos-Padilla Mauricio3, 4, 5, Besnard Lucien2, Munaron Jean-Marie2, Le Loch Francois2, Point David1
Affiliation(s) 1 : Géosciences Environnement Toulouse (GET), Observatoire Midi Pyrénées (OMP), UMR 5563 CNRS/IRD/Université Paul Sabatier, 14 Avenue Edouard Belin, 31400, Toulouse, France
2 : Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280, Plouzané, France
3 : Pelagios Kakunjá A.C., Sinaloa 1540, Las Garzas, 23070, La Paz, Baja California Sur, Mexico
4 : Centro de Investigaciones Biológicas del Noroeste (CIBNOR), La Paz, Baja California Sur, 23096, Mexico
5 : Fins Attached Marine Conservation, Colorado Springs, USA
Source Chemosphere (0045-6535) (Elsevier BV), 2020-08 , Vol. 253 , P. 126645 (10p.)
DOI 10.1016/j.chemosphere.2020.126645
WOS© Times Cited 1
Keyword(s) Top-predators, Mercury transfer, Food webs, Foraging habitat, Stable isotopes, MPAs
Abstract

Worldwide shark populations have experienced rapid declines over the last decades, mainly due to overfishing. Marine protected areas (MPAs) have thus become an indispensable tool for the protection of these marine predators. Two recently-created MPAs in the Northeast Pacific Ocean, the Revillagigedo National Park and Clipperton atoll, are characterized by different trophic structures potentially influencing trophic niche and contaminant exposure for resident sharks in these two sites. In this context, we used carbon (δ13C) and nitrogen (δ15N) stable isotope analyzes as well as total mercury concentrations ([THg]) to assess the role of foraging site on the trophic niche and Hg levels of juvenile ST sharks Carcharhinus albimarginatus. Analyzing fin clip samples from both Revillagigedo and Clipperton, we found that shark δ15N varied spatially in relation to δ15N baselines, suggesting similar trophic position in both MPAs. Moreover, δ13C values indicated that ST sharks from Revillagigedo would feed on different food webs (i.e. both benthic and pelagic) while individuals from Clipperton would only rely on benthic food webs. These differences between MPAs led to a weak overlap of isotopic niche between the two populations, highlighting site residency for juvenile ST sharks. Within populations, [THg] was not correlated to trophic tracers (δ15N and δ13C) and was also similar between populations. This study revealed no influence of site or food web in [THg] and raises the question of the origin of Hg exposure for reef shark populations in the Northeast Pacific Ocean.

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Le Croizier Gaël, Lorrain Anne, Schaal Gauthier, Ketchum James, Hoyos-Padilla Mauricio, Besnard Lucien, Munaron Jean-Marie, Le Loch Francois, Point David (2020). Trophic resources and mercury exposure of two silvertip shark populations in the northeast Pacific Ocean. Chemosphere, 253, 126645 (10p.). Publisher's official version : https://doi.org/10.1016/j.chemosphere.2020.126645 , Open Access version : https://archimer.ifremer.fr/doc/00619/73114/