Shipping noise in whale habitat: characteristics, sources, budget, and impact on belugas in Saguenay-St. Lawrence Marine Park hub.

A continuous car ferry line crossing the Saguenay Fjord mouth and traffic from the local whale-watching fleet introduce high levels of shipping noise in the heart of the Saguenay-St. Lawrence Marine Park. To characterize this noise and examine its potential impact on belugas, a 4-hydrophone array was deployed in the area and continuously recorded for five weeks in May-June 2009. The source levels of the different vessel types showed little dependence on vessel size or speed increase. Their spectral range covered 33 dB. Lowest noise levels occurred at night, when ferry crossing pace was reduced, and daytime noise peaked during whale-watching tour departures and arrivals. Natural ambient noise prevailed 9.4% of the time. Ferry traffic added 30-35 dB to ambient levels above 1 kHz during crossings, which contributed 8 to 14 dB to hourly averages. The whale-watching fleet added up to 5.6 dB during peak hours. Assuming no behavioral or auditory compensation, half of the time, beluga potential communication range was reduced to less than ~30% of its expected value under natural noise conditions, and to less than ~15% for one quarter of the time, with little dependence on call frequency. The echolocation band for this population of belugas was also affected by the shipping noise.