engleski

Annual characterization of sea ambient noise in the Lošinj – Cres archipelago (Croatia) and its impact on bottlenose dolphin distribution

In order to assess the extent of anthropogenic pressure, in terms of type and intensity of noise and presence of vessels, on the bottlenose dolphin distribution the Sea Ambient Noise (S.A.N.) was measured between November 2004 and October 2005. Recordings from 10 acoustic stations within Losinj-Cres archipelago (Croatia) allowed acoustical characterization of the area. The S.A.N. resulted to be a good indicator of presence of the anthropogenic noise. Boats and ships are responsible for most of the man-made noise and, in the areas with strong nautical tourism, they increase the S.A.N. in the low frequency bands mostly. Recordings of noise and data on vessel presence were compared to data on spatial distribution of bottlenose dolphins’ groups. A clear correlation between the area with high anthropogenic pressure and a strong dolphin avoidance of the same area was found, mostly during the summer months. The avoidance of this specific area can be attributed to a seasonal significant increase of the total number of boats, particularly of very fast and noisy vessels such as speed boats and motor yachts, usually with inboard or outboard engines with power of more then 100 HP.

sea ambient noise; bottlenose dolphin; Tursiops truncatus; Lošinj; Adriatic sea

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