Since sound from Atlantic cod (Gadus morhua) plays a significant role during their spawning activities, it is imperative to gain insights into their sound pressure levels. This knowledge is particularly valuable for understanding how cod responds to anthropogenic sounds, such as the intense sound from seismic air guns. In field experiments within sea cages using multiple instruments, including underwater cameras, a hydrophone, and an underwater acoustic vector sensor (AVS), the source level of cod grunts was scientifically measured. The measurements yielded an estimated median source level of 123.1 dB re 1 µPa at 1 m (121.8–124.2 dB, 95% confidence interval). The compact AVS measured collocated acoustic pressure and acoustic particle motions in three dimensions, providing valuable information regarding acoustic directionality in addition to sound pressure. This directional information assists in detecting the grunt bearing, estimating probable grunt propagation ranges, and subsequently reducing uncertainties associated with the estimation of the grunt source level. These experiments have demonstrated the AVS measured the cod vocalisations with directional information and can be potentially broadly used in other marine bioacoustics monitoring and tracking research.
Atlantic cod, grunt, source level, underwater acoustic vector sensor, acoustic bearing