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Abundance of Risso's dolphins (Grampus griseus) in the Algarve, Portugal, using photo-ID
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Resumo(s)
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.
Descrição
Tese de mestrado, Ecologia Marinha, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
população modelos captura-recaptura multimark foto-identificação cetáceos Teses de mestrado - 2024