Settings of demersal longlines reveal acoustic cues that can inform toothed whales where and when to depredate

Fishing boats produce acoustic cues while hauling longlines. These acoustic signals are known to be used by odontocetes to detect the fishing activity and to depredate. However, very little is known about potential interactions before hauling. This article describes the acoustic signature of the setting activity. Using passive acoustic recorders attached to the buoys of longlines, this work demonstrates an increase in the ambient sound of ~6dB re 1 µPa² /Hz within 2–7 kHz during the setting activity. This could also be used as an acoustic cue by depredating species, suggesting that predators can detect longlines as soon as they are set.