Abstract
The whale‐watching activity has been growing in the Azores during the last 15 years. To contribute to the sustainability and management of the activity it is crucial to monitor its influence on cetacean populations. This work aimed to determine the sound produced by whale‐watching boats, in terms of frequencies and sound pressure levels (SPLs). Different types of boats were recorded between May and Sept. 2007 around the islands of Faial, Pico, and S. Miguel. Recordings were made with a hydrophone from a drifting platform. The whale‐watching boats carried out several tracks with different speeds and changed gear (forward/reverse). SPL values varied between 74 and 116 dB re 1 μPa (1/3 octave band level) for both outboard and inboard engines, without any obvious difference between the two. One inboard catamaran produced 106 dB re 1 μPa at 50 kHz (18 knots, 50 m distance), which is higher than all the other SPLs, at the same frequency. Forward/reverse maneuvers in inboard engines had lower frequencies but a l...
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