To assess the status of populations, it is essential to obtain detailed data on the population under study, including its distribution. Such information is vital for implementing conservation strategies tailored to the specific needs of the species or population. However, determining these parameters poses challenges, as cetaceans spend the most of their life underwater.. The aim of this study is to assess demographic parameters, such as population size, recruitment, survival rates, and capture rates of Risso’s dolphins, Grampus griseus (Cuvier, 1812), along the southern coast of Portugal. Data was collected between 2010 and 2022, during various months. The study area included the coastal waters of Albufeira and Sagres, where significant environmental features, such as submarine canyons and Mediterranean eddies, influence the dolphins’ presence. For obtaining estimates of the demographic parameters, photo-identification is a widely used method. This non-invasive, cost-efficient technique is particularly valuable for studying endangered species. For dolphins, the method involves photographing their dorsal fin to register identifying features such as scars and notches, which aid in the identification of individual animals. The resulting data is the used in capture-recapture models to estimate key demographic parameters. These models are divided into categories: closed population models, which assume no demographic changes occur, and open population models, which account for processes such as birth, death, immigration and emigration. According to Red List of Endangered Animals of the International Union for Conservation of Nature (IUCN), the Risso’s dolphin, is classified as Least Concern. Nonetheless the species is under international protection by Annex IV of the European Union Habitats Directive. Globally, this species is distributed in tropical to temperate waters in both hemispheres. In Portugal there have been records of sightings in the Azores archipelago mostly, with additional occurrences along the southern Portugal coast – which requires further research to better understand the population’s trends.

Tese de mestrado, Ecologia Marinha, 2024, Universidade de Lisboa, Faculdade de Ciências