4.2 Article

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

Journal

MARINE ECOLOGY PROGRESS SERIES
Volume 664, Issue -, Pages 149-163

Publisher

INTER-RESEARCH
DOI: 10.3354/meps13640

Keywords

Trophic markers; Nutritional condition; Dietary patterns; Tiger shark; Galeocerdo cuvier; Reproduction; Trophic ecology; Physiology

Funding

  1. Disney Conservation Fund
  2. International SeaKeepers Society
  3. Batchelor Foundation Inc
  4. Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP [2014/16320-7, 2017/25273-0]

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This study investigated the nutritional status and trophic dynamics of female tiger sharks across different life stages using non-lethal methods. Results showed that female tiger sharks adjusted their diet and fatty acid metabolism depending on their reproductive context, suggesting changes in their nutritional requirements associated with reproductive state. These findings provide insights into the expected changes in nutritional and trophic markers across life stages of female tiger sharks.
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 (17 beta-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.

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