Ecophysiology and trophic relationships of elasmobranchs: biomarkers as tools for conservation

Author(s)

Bianca de Sousa Rangel

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2023-02-03

Examining board members

Renata Guimarães Moreira Whitton; Carolina Arruda de Oliveira Freire; Domingos Garrone Neto; Aline Dal Olio Gomes

• Advisor: Renata Guimarães Moreira Whitton; Neil Hammerschlag

Abstract

Given the high diversity in life-history strategies, elasmobranchs (sharks and rays) become interesting models for the study of relationships between physiology and ecological interactions in the marine environment. Although efforts to conserve elasmobranchs, which are currently the second most endangered group among vertebrates on the planet, have stimulated an increase in the number of studies on ecological patterns and anthropic impacts, little is known about their physiology. Thus, in this Ph.D. thesis, seasonal and spatial physiological variations associated with the life-stage and behavior of sharks from different life histories were investigated. It was used multiple non-lethal tools to provide a better understanding of energetic and reproductive patterns, as well as a physiological basis that helps predict the effects of environmental disturbances on sharks. The chapter 1 addresses inter- and intraspecific variations in the nutritional ecology of sharks with different life-history strategies within a protected oceanic island system, the Fernando de Noronha Archipelago. Variations in dietary patterns and nutritional and metabolic status related to reproduction of female tiger sharks Galeocerdo cuvier (chapter 2) and males of nurse sharks Ginglymostoma cirratum and blacktip sharks Carcharhinus limbatus (chapter 3) were also addressed. Chapters 4, 5 and 6 address the effects of urban living on the nutritional status and diet patterns of sharks with different lifestyles, the nurse, blacktip and tiger shark, respectively. The results showed that the influence of urbanization on the quality of the sharks\' diet seems to be more pronounced in sedentary species, such as the nurse shark, when compared to more active species. Finally, chapter 7 brought a new approach to shark research, combining multiple physiological markers with information obtained through ultrasound and passive acoustic telemetry to understand relationships between the physiological aspects and behavior of tiger sharks exposed to food provisioning tourism. The results showed that life-stage, endocrine regulation, and nutritional condition influence and/or are influenced by the time that sharks spend interacting with provisioning tourism. Taken together, the results showed that the nutritional, reproductive and metabolic biomarkers used in this thesis provide a powerful tool to describe complex ecological patterns in sharks, especially when combined with other technologies for tracking movement and identifying the reproductive stage of sharks. (AU)

• FAPESP's process: 17/25273-0 - Ecophysiology and trophic relationships of elasmobranchs: biomarkers as tools for conservation
• Grantee: Bianca de Sousa Rangel
• Support Opportunities: Scholarships in Brazil - Doctorate