Controlled exposure experiments with operational marine vibrators and very-low frequency whales

Marine geophysical surveys use acoustic imaging sources including airguns that generate intense impulsive broad-band noise, though only <200 Hz is practically useful. Marine vibrators (MV) have been developed as reduced-impact alternatives to concentrate energy in this band with lower rise time and peak pressure. These parameters presumably reduce impacts on species that use higher frequencies but key questions remain for species that utilize very low frequencies, including large whales. We conducted controlled exposure experiments (CEE) to obtain novel baseline and experimental behavioral response data for very low-frequency whales to a full-scale, realistic, operational MV. We focused on blue and fin whales off Californiausing multi-scale tags, including longer duration (weeks) dart-attached and shorter (days) suction-cup attached high-resolution depth, movement, and acoustic tags. The MV source produced repeated 5-s, 5–100 Hz linear sweeps at 50% duty cycle and 190 dB re:1mPa (broadband RMS). 33 tags yielded ∼2500 h of data in eight 90-min CEEs (6 MV; 2 no-noise “control"). Pilot CEEs with simulated MVs indicated mild, temporary avoidance responses by traveling whales or those feeding in lower prey densities. Initial data from operational MVs did not indicate broad-scale avoidance or strong behavioral changes for blue whales feeding intensely on concentrated prey.