Virtual library - Master's dissertations
- Master's dissertation title: Monitoring of marine mammals during seismic surveys off the Northeastern Brazil
- Institution: Federal University of Pernambuco
- Supervisor: Maria Elisabeth de Araújo
- Year of defense: 2005
Marine seismic surveys involve the use of high energy noise sources operating in the water column to probe below the seafloor. The high energy levels involved in seismic surveys have raised special concern in regards to marine mammals. A monitoring program to verify the occurrence of marine mammals was carried out during five seismic surveys in four areas of the Northeastern region of Brazil. Seismic surveys occurred between June, 2002 and August, 2003. The method used to monitor these marine mammals was visual observation from the source vessel (Gunboat), cable lay-out boats and dedicated observation vessel during day and night time. It was analyzed the effectiveness of the marine mammal observations to answer about impacts of airguns activity. Eighty-three sightings of marine mammals were recorded as follow: Tursiops truncatus (14), Stenella frontalis (11), Megaptera novaeangliae (10), Sotalia fluviatilis (6), Stenella sp. (2), Steno bredanensis (2), and Trichechus manatus (4). Thirty-four cetaceans were identified just as Odontoceti. The sightings varied in depths between 2-50m and at distances of 2-5000m from the sources. The observations were influenced by day time, visibility, observer experience and methodology. The methodology was not effective to answer about airguns activity over marine mammals. It is recommended some procedures to improve the marine mammals monitoring activity.
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