February 1st to 5th 2016
Olhão, Portugal
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Occurrence patterns of individual Bottlenose dolphins (Tursiops truncatus) in coastal waters of SW Portugal

Scientific Exhibition
Habitat Loss and Ocean Noise
Thursday, February 4, 2016 -
17:30 to 19:30

Magalhães, S.M. 1

1Mar Ilimitado, Tourism & Research

The presence of common bottlenose dolphins (Tursiops truncatus) is documented in Portugal mainland, but studies of the species focus mainly on a well known resident population in Sado estuary and only very recently also on animals occurring in the adjacent coastal area. This species is one of the best known and widespread of the small cetaceans, occurring throughout the world’s tropical and temperate seas and oceans. Coastal bottlenose dolphins tend to form resident, transient or temporary migrant populations across their distribution range. This study aims to analyse for the first time the occurrence patterns of individual dolphins of this species in the coastal area of SW Portugal mainland. Data available (geographic location, group size, composition and images of individual animals) was collected by one qualified observer onboard of platforms of opportunity (dolphin watching) between 2007 and 2015 in the coastal area between Sagres and Lagos, and covered all seasons of the year. The identification of individual animals using photographs of natural markings (photo-identification) was the key method used. A total of 288 individual dolphins were identified so far, of which 38.9% were sighted in more than one occasion. Few of the animals re-sighted more than once occurred in different years and seasons, showing some degree of residency and site fidelity. Results also indicate that we are in the presence of an open population, as new individuals are constantly being identified. This information has implications for conservation, as Bottlenose dolphins are listed in Annex II of the European Union’s Habitats Directive and EU governments are required to consider the areas where this species occurs for the establishment of Special Areas of Conservation (SACs). This study also contributes to the knowledge of the ecology of bottlenose dolphin populations occurring in coastal waters of Portugal mainland.

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