Erbe, C. 2002. Underwater Noise Of Whale-Watching Boats and Potential
Effects on Killer Whales (Orcinus orca), Based on an Acoustic Impact
Model. Marine Mammal Science: Vol. 18, No. 2, pp. 394-418.
Fisheries & Oceans Canada, Institute of Ocean Sciences, 9860 W Saanich
Road, Sidney, British Columbia V8L 4B2, Canada E-mail: email@example.com
Underwater noise of whale-watching boats was recorded in the popular
killer whale-watching region of southern British Columbia and
northwestern Washington State. A software sound propagation and impact
assessment model was applied to estimate zones around whale-watching
boats where boat noise was audible to killer whales, where it
interfered with their communication, where it caused behavioral
avoidance, and where it possibly caused hearing loss. Boat source
levels ranged from 145 to 169 dB re 1 Pa @ 1 m, increasing with speed.
The noise of fast boats was modeled to be audible to killer whales
over 16 km, to mask killer whale calls over 14 km, to elicit a
behavioral response over 200 m, and to cause a temporary threshold
shift (TTS) in hearing of 5 dB after 30-50 min within 450 m. For boats
cruising at slow speeds, the predicted ranges were 1 km for audibility
and masking, 50 m for behavioral responses, and 20 m for TTS.
Superposed noise levels of a number of boats circulating around or
following the whales were close to the critical level assumed to cause
a permanent hearing loss over prolonged exposure. These data should
be useful in developing whale-watching regulations. This study also
gave lower estimates of killer whale call source levels of 105-124 dB
re 1 Pa.