Historical ecology of the Mediterranean population of the Great White Shark, Carharodon Carcharias, from museum collection

The Great White Shark, Carcharodon carcharias, is Critically Endangered in the Mediterranean due to its low population density and the absence of conventional aggregation sites, hampering data collection and reconstruction of the population behavioral ecology. Historical collections, being a repository of past biodiversity, can overcome these issues for a better understanding of fundamental processes such as paleo-ecological changes. In this perspective, this work deals with the historical ecology of the Mediterranean white shark population through a multi-element analysis of stable isotopes (carbon, nitrogen, zinc, and strontium) of 5 historical remains archived in Italian museums and private collections. Using individual vertebrae (N = 4), we provide information about the ontogenetic shifts and the trophic ecology by the estimate of the isotopic composition of carbon, nitrogen, and zinc from the vertebral collagen, and date back one fossil tooth using strontium isotope composition. The main results show that: 1) isotopic values of nitrogen confirmed the white shark as a top predator, 2) the diet is based on dolphins and fishes, 3) the zinc analyses revealed a strong difference between the pre-birth and post-birth isotopic composition 4) the dating of the fossil tooth confirmed the Miocene-Pliocene presence in the Mediterranean. Overall, these multi-element isotope approaches have the potential to obtain important information on developmental physiology, ecology, and behavior of the poorly studied Mediterranean white shark, highlighting the fundamental role of historical remains for an overall knowledge of shark life-history, avoiding invasive sampling and analysis.