Behavioural effects of exposure to underwater explosions in humpback whales (Megaptera novaeangliae)

Abstract

Humpback whale (Megaptera novaeangliae) entrapment in nets is a common phenomenon in Newfoundland. In 1991 – 1992, unusually high entrapment rates were recorded in Trinity Bay on the northeast coast of Newfoundland. The majority of cases occurred in the southern portion of the bay close to Mosquito Cove, a site associated with construction operations (including explosions and drilling) that presumably modified the underwater acoustic environment of lower Trinity Bay. This study reports the findings of the resulting assessment conducted in June 1992 on the impact of the industrial activity on humpback whales foraging in the area. Although explosions were characterized by high-energy signatures with principal energies under 1 kHz, humpback whales showed little behavioural reaction to the detonations in terms of decreased residency, overall movements, or general behaviour. However, it appears that the increased entrapment rate may have been influenced by the long-term effects of exposure to deleterious levels of sound.