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Oceans of noise - Whale and Dolphin Conservation Society

Oceans of noise - Whale and Dolphin Conservation Society

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• There was no evidence <strong>of</strong> minke whales approaching vessels travelling at survey speeds <strong>and</strong>some avoidance behaviour was noted.Ref: Tillman <strong>and</strong> Donovan 1986.Species type: Common minke whale, Balaenoptera acutorostrataLocation: Tokyo Bay, Japan.• It was suggested that postwar decreases in minke whale, Balaenoptera acutorostrata catchesin Tokyo Bay were the result <strong>of</strong> increased boat traffic <strong>and</strong> changes in the distribution <strong>of</strong> thesespecies. However, the declines may have been due to the impacts <strong>of</strong> commercial whalingcausing a decline in numbers <strong>of</strong> these whale species rather than effects <strong>of</strong> boat traffic.Ref: Nishiwaki <strong>and</strong> Sasao 1977.Bowhead whales, Balaena mysticetusLocation: Beaufort Sea• Bowhead whales avoiding boat traffic do so when receiving only relatively low levels <strong>of</strong>vessel produced <strong>noise</strong>. A 13m diesel powered boat produced an avoidance reaction in abowhead whale with a received <strong>noise</strong> level <strong>of</strong> only 84 dB re µ1Pa. This received level was c.6dB above the ambient <strong>noise</strong> levelRef: Richardson 1995.Location: Beaufort Sea• Bowhead whales, Balaena mysticetus, exhibited various reactions, including changes <strong>of</strong>observed behaviour <strong>and</strong> alteration <strong>of</strong> diving <strong>and</strong> respiratory behaviour, when approached by avariety <strong>of</strong> vessel types.• Bowhead whales 0.5km to the side or behind a vessel seemed unaffected <strong>and</strong> on occasionsapproached within 100-500m <strong>of</strong> the vessel when the vessel was not manoeuvring towards thewhales.• These whales tolerated broadb<strong>and</strong> <strong>noise</strong> levels <strong>of</strong> up to 110-115dB re µ1Pa.• It was suggested that bowhead whales actively engaged in mating/social behaviour may beless responsive to boat traffic.• One radio-tagged bowhead whale was approached by a small boat for a period <strong>of</strong> three days.Dive times were reduced when the boat approached within 500m for a period <strong>of</strong> 90-150minutes. For a period <strong>of</strong> three days after the approaches by the small boat, diving behaviourreturned to normal <strong>and</strong> the whale remained in the general area that the vessel was operatingin.Ref: Wartzok et al. 1989.153

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