Whale observations and acoustic noise measurements around Kahoolawe Island, Hawaii

Abstract

Seven SSQ-57A sonobuoys were monitored for seven hours from a P-3 aircraft during a surface gunfire operation north of Kahoolawe Island, Hawaii, in February 1980. Whale location and activity were also monitored from the aircraft and from Maul Island during the exercise. Humpback whale (Megaptera novaeangliae) phonations dominated the ambient noise field during the exercise. The phonations' fundamental component was near 500 Hz. The gunfire source level was approximately 10 dB below the whales' phonation level; the gunshots' peak energy was near 70 Hz. We saw whales swimming, lying still, diving, surfacing and, in two isolated instances, breeching and lob-tailing. No standards exist to evaluate the effects of the noise on marine mammals. We cannot relate the movements and activities of whales observed during the exercise to any obvious airborne, surface, or subsurface causes. [Work supported by the Naval Surface Weapons Center.]