Abstract: The ramp-up is a standard procedure within the offshore geophysical industry for mitigating the potential impacts of seismic airgun sound on marine mammals. However, the efficiency of the ramp-up as a mitigating procedure is poorly documented. In March 2008, a pod of 15 short-finned pilot whales (Globicephala macrorhynchus) was monitored before, throughout, and following a 30-min ramp-up procedure during a 2-D seismic survey off Gabon. No change in behaviour was apparent during the initial period of the ramp-up. However, 10 min into the ramp-up procedure (at airgun volume of 940 cu3), the nearest whale subgroup turned sharply away from the airguns. Subsequent behaviour included milling, tailslapping, and a 180° change of course to travel in the opposite direction from the seismic vessel. The observation described here suggests that pilot whales did initially demonstrate an avoidance response to the ramp-up. However, the movement away from the source was limited in time and space. Recommendations are made for further research into the efficiency of the ramp-up procedure for marine mammal mitigation.

Key Words: Short-finned pilot whale, Globicephala macrorhynchus, airguns, ramp-up, Gabon, seismic survey, geophysical survey

Document Type: Research article

DOI: 10.1578/AM.34.3.2008.349

Page Numbers: 349-354