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

Abstract

Throughout the life cycle, the animals deal with changes in nutritional status associated with changes in the diet, growth, reproduction and migration. Given the diversity in life-history, elasmobranchs become interesting models for the study of relationship between physiology and ecological interactions in the marine environment. Despite recent studies on ecological patterns and physiological differences in elasmobranchs, related to habitat use and phylogeny, very little is known about the effects of seasonal variations, reproduction and ontogeny in trophic interactions. Alternative methods, non-lethal, using trophic markers, as the fatty acids (FA) and stable isotope (SI), are well established to investigate trophic and metabolic aspects in consumers, enabling the integration of temporal information. This project will characterize the FA profile, associated with the isotopic signature and the sex steroid hormones in elasmobranchs from different life history strategies, in two regions of biological importance: (1) nursery area, in the coastal region of Bertioga, SP, Brazil, and (2) feeding area, on the southern coast of Florida, USA. Due to the scarcity of some species and the logistic difficulties, part of the samples will be incorporated into the monitoring and marking program of the University of Miami. The composition of FA and SI signature of nitrogen (´15N) and carbon (´13C) will be analyzed in tissue and plasma, checking individual and interspecific nutritional status. We intend, with these biomarkers, to identify resource partitioning among sympatric species over time, relating with the biological traits of each species (reproduction and habitat use), providing information of mesopredator and top predators for monitoring studies and evaluation of potential anthropic impacts. (AU)