Cetaceans occurrence off the west central Portugal coast: a compilation of data from whaling, observations of opportunity and boat-based surveys

Throughout the years some researchers have dedicated their efforts to the study of cetaceans’ occurrence off Mainland Portugal. However, it is still missing a systemic scientific methodology for studying the presence of coastal dolphins and whales. This work intends to be a first approach on the occurrence of cetaceans off the west central coast of Portugal. Our objective was to contribute towards the compilation of relevant “forgotten science” such as whaling data and observations of opportunity, together with two years of boat-based surveys. We found 1313 occurrences of great whales captured off Setúbal and Sesimbra (1925-1927 and 1944-1951) and a total of 45 cetaceans in non-directed captures between 1976 and 1978. We accounted 45 dolphins and whales in sea-sightings as a result of observations of opportunity, from 2002 to 2008. In 2007 and 2008 a total of 63 boat-based visual surveys were conducted from three different geographic locations, Nazaré, Peniche and Sesimbra, and as a result 45 independent sightings of cetaceans were recorded. The most frequent small dolphin off the Portuguese mainland coast is the common dolphin (Delphinus delphis) as shown by the three distinct approaches used in this study. Regarding whales the most common species is the fin whale (Balaenoptera physalus) as shown by whaling records. Overall, the small delphinid community along the central coast of Portugal is similar to the one that can be found along the Iberia shore.