Unveiling the Past: Assessment of Historical Ecology and Baseline Shifts of Mediterranean Angel Sharks

The Mediterranean Sea hosts to three angel shark species (Squatina) listed as Critically Endangered by IUCN. Their slow growth, late maturity, and low reproductive rates make them highly vulnerable, impeding population recovery. As benthic predators, play a vital role in maintaining marine ecosystem balance. The recent decline of these species highlights the urgent need to understand the factors driving their decrease and its conservation implications. In this study, we used museum specimens and a multidisciplinary approach to assess the historical species and ecological diversity of Mediterranean angel sharks. We drew on historical osteological and wet specimens from the 19th to 21st centuries, sourced from over 30 museums and private collections across the Mediterranean region. We employed traditional and geometric morphometry species identification techniques, complemented by ancient DNA and multi-element stable isotope analyses. Preliminary data allowed us to distinguish 53 specimens of Squatina sp., through morphometric analysis. New extraction techniques enabled us to obtain DNA from formalin-preserved samples, allowing species-level identification for individuals unsuitable for morphometric analysis. We also create a comprehensive Mediterranean stable isotope database using historical elasmobranch remains. This database provides a robust framework for future stable isotope analysis, offering insights into the dietary habits and ecological roles of angel sharks and other elasmobranchs over time. Moreover, this research aims to make the collection accessible to researchers and highlight the significant contribution of natural history museum collections to the knowledge and conservation of elasmobranchs. It also seeks to strengthen the commitment to marine biodiversity protection and environmental education.