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Marine Ecology Progress Series

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MEPS 664:149-163 (2021)  -  DOI:

Dietary and reproductive biomarkers in a generalist apex predator reveal differences in nutritional ecology across life stages

Bianca de Sousa Rangel1,*, Neil Hammerschlag2,3, James A. Sulikowski4, Renata Guimarães Moreira1

1Laboratório de Metabolismo e Reprodução de Organismos Aquáticos, Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, travessa 14, 321, Cidade Universitária CEP 05508-090, São Paulo, SP, Brazil
2Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA
3Leonard and Jayne Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL 33146, USA
4School of Mathematical and Natural Sciences, Arizona State University, Glendale, AZ 85306, USA
*Corresponding authors:

ABSTRACT: Knowledge of the nutritional requirements of apex predators is key for determining ecological interactions. However, an understanding of how diet is influenced by reproduction, and the consequences of foraging variation on the nutritional status of a predator, is limited. Here, we used short-term dietary markers (plasma and whole-blood fatty acids) integrated with reproductive hormones (17β-estradiol and testosterone) and ultrasonography as a non-lethal approach to investigate the effect of life stage on nutritional status and trophic dynamics of female tiger sharks Galeocerdo cuvier. Despite their generalist feeding behavior, female tiger sharks fed on different food sources and/or modulated their fatty acid metabolism depending on the reproductive context. This suggests some adjustment in their nutritional requirements associated with changes in their reproductive state. Plasma and whole-blood fatty acids indicated distinct dietary sources across life stages, with a high dependence on coastal/benthic food resources during juvenile life stages, and on pelagic/oceanic and reef-associated food resources during adult life stages. Higher percentages of highly unsaturated omega-3 fatty acids found in females during their reproductive cycles suggest the dependency on these fatty acids as a source of metabolic energy during reproduction. A high percentage of arachidonic acid (ARA) found in plasma of gravid females suggests the possibility of a selective diet of ARA-rich prey species and/or selective mobilization of ARA from stored energy during gestation. Based on our findings, we propose a conceptual model of expected changes in nutritional and trophic markers across life stages of female tiger sharks.

KEY WORDS: Trophic markers · Nutritional condition · Dietary patterns · Tiger shark · Galeocerdo cuvier · Reproduction · Trophic ecology · Physiology

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Cite this article as: Rangel BS, Hammerschlag N, Sulikowski JA, Moreira RG (2021) Dietary and reproductive biomarkers in a generalist apex predator reveal differences in nutritional ecology across life stages. Mar Ecol Prog Ser 664:149-163.

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