Marjorie Lyssikatos, chair of ICES Working Group on Bycatch of Protected Species (WGBYC).
'A pinger is an acoustic deterrent device (ADD) primarily used on gillnet fishing gear as a tool for 'alerting' and thereby deterring marine mammals away from entangling gear. Pingers have generally become accepted around the world as a means of reducing accidental bycatch mortality of harbor porpoise in gillnets.
The way it works is a sound or 'ping' is emitted from the device at various frequencies and time intervals (depending on member country policies and regulations) considered optimal for altering and deterring animals away from the entangling gear.
Current research is looking, amongst other things, at the effectiveness of pingers on other species and on habituation (animals becoming desensitized over time to the sound emitted from pingers).'