Abstract
Carcharodon carcharias is a protected species occupying the apex of most marine foodwebs where they are present. Aggregation areas, such as Guadalupe Island, México, that have been related to feeding events, are of special interest for this species conservation. The aim of this study was to describe the fatty acid profile of C. carcharias' muscle for the first time on Guadalupe Island, using non-lethal biopsy methods to determine ontogenetic and sex differences in relation to diet and habitat use. Fatty acid profiles and biomarkers from different individuals are explored as a source of integrated information of their diet. Analysis of the fatty acid composition of individuals with varying total lengths (2.3-5.0 m) suggested a dietary shift between juveniles and adults occurring at aproximately 3 m. Fatty acid biomarkers indicated a higher degree of carnivorism in adults than in juveniles. Additionally, these ecological tracers suggested that juveniles feed in shallow waters close to the coast, while adults feed in deep waters along inshore and offshore areas. This study represents a first step towards using fatty acid composition as a relevant tool for further understanding dietary shifts and habitat use throughout the ontogeny of C. carcharias. However, to corroborate this, further studies with larger sample sizes are required.
Highlights
Carcharodon carcharias (Linnaeus, 1758) occupies the apex of most marine foodwebs where present (Bonfil et al 2005)
Total saturated fatty acids (SFA) accounted for 35.2 ± 5.3%, polyunsaturated fatty acids accounted for 21.8 ± 6.3% and monounsaturated fatty acids accounted for 19.5 ± 3.9%
The results of this study suggest intraspecific differences in FA composition of the muscle of Carcharodon carcharias, which might be related to factors such as diet, habitat use, and to selective conservation of FAs necessary for physiological processes such as reproduction (Bell et al 1985, 1992; Pethybridge et al 2010, Rodriguez-Barreto et al 2012, Beckmann et al 2013, Couturier et al 2013b, Davidson et al 2014, Pethybridge et al 2014, Meyer et al 2017, 2019)
Summary
Carcharodon carcharias (Linnaeus, 1758) occupies the apex of most marine foodwebs where present (Bonfil et al 2005). Several studies have suggested elasmobranchs cannot synthesize long chain polyunsaturated fatty acids (LC-PUFA) considered as essential nutrients for several physiological processes (Brett & Müller-Navarra 1997, Tocher 2010, Sardenne et al 2017) Instead, these FAs must be transferred across food webs through diet (Dalsgaard et al 2003, Iverson et al 2004), likely influencing trophodynamics (Caraveo-Patiño et al 2009, Sardenne et al 2017) and can be used to track dietary items (e.g., diatoms and/or dinoflagellate origin) the predator is feeding on (Couturier et al 2013a)
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