Cetacean monitoring in Northeastern Atlantic Ocean – Occurrence and distribution for cetacean species in the Canary Basin

Cetaceans are ecologically important as storers and transporters of energy in marine ecosystems. They are top-down regulators maintaining the prey-predator balance in these complex and dynamic environments. Therefore, the understanding of cetacean distribution and habitat preferences represents a priority issue in marine conservation being an important support for management plans. In the Atlantic Ocean there are, at least, 30 cetacean species, but their distribution is poorly understood. Data come from few regional ‘hot-spots’ (e.g. Azores and Madeira), where research effort limits data collection to a few miles from the coast. Therefore, the knowledge about cetacean distribution in the Atlantic has to be considered very localized and not representative of the overall Northeastern Atlantic area. Cargo ships from Transinsular Company were used as Observation Platforms of Opportunity, specifically the routes from Continental Portugal (Lisbon and Oporto) to Madeira Island (Caniçal) and vice-versa, to collect data on cetacean occurrence, from July to October, 2012. A total of 113 sightings were recorded, with an encounter rate (ER) of 0.0220 sightings/nautical mile (NM) on 5136 NM on effort. A total of 7 species were identified: Tursiops truncatus, Delphinus delphis, Balaenoptera acutorostrata, Ziphius cavirostris, Physeter catodon, Stenella frontalis and Globicephala macrorhynchus. The most spotted specie was Tursiops truncatus with 21% and an ER of 0.0047 sightings/NM. Dolphins had the highest ER (0.0136 sightings/NM) representing 62% of the sightings, followed by toothed whales with an ER of 0.0039 sightings/NM and 18% of the sightings and baleen whales (Minke whales and 3 sightings of Balaenoptera sp.) with an ER of 0.0035 sightings/NM and 16% of the sightings. There were 5 sightings of non-identified cetaceans. Cetacean monitoring can act as a strong tool and support for conservation plans. Therefore, maintaining these monitoring surveys can improve the knowledge on cetacean presence and distribution in the NE Atlantic Ocean.