Vast assembly of vocal marine mammals from diverse species on fish spawning ground

This published paper utilizes data from an acoustic low frequency system to collect information on prey distribution and abundance as well as distribution and activity of their top predators. The system transmits broadband signals from 700 - 1500 Hz and a towed array receives the returned echoes used in the assessment of prey abundance and distribution. Periodically, only the receiver array was operated to listen to whale vocalization. The vocalization identifies the animals and the long array enables precise positioning. This quasi simultaneous predator-prey coverage produce new information about species interactions both intraspecific predator relations as well as interaction between predators and prey. The Ocean Acoustic Waveguide Remote Sensing (OAWR) system is at present tailored to swimbladdered fish and exploits their resonance frequency for sizing and identification purposes. To become suitable for krill and whale interaction we might need to increase the frequency range. However, the methodology offer coverage of 10s of km and may thus inform about variability issues now causing troubles in the assessment of krill using conventional acoustic methods.