Seal scarers, also termed Acoustic Mitigation Devices, Acoustic Deterrent Devices (ADDs) or Acoustic Harassment Devices (AHDs) are used increasingly to deter marine mammals (seals, sea lions, whales, dolphins and porpoises) from approaching impulsive sounds, such as pile driving (windfarm), conductor driving (drilling) or Unexploded ordnance (UXO), especially where a soft start is not possible or effective. The Lofitech is often confused with the term ‘pinger’, which is a much lower-powered device, serving an entirely different purpose. In German waters, seal scarers must be used by law if a sound source exceeds a certain level (see www.osc.co.uk/sectors/windfarms/ for more information on this).
Seal scarers can be effective at encouraging animals (especially harbour porpoises, Phocoena phocoena) to move away from high risk operational areas by producing a loud noise that a species may find aversive. Seal scarers are used typically for 15 minutes before the impulsive sound, allowing animals enough time to clear a mitigation zone (usually 1000 m) from the sound source.
Lofitech seal scarer
One make of ADD used by Ocean Science Consulting is the Lofitech seal scarer. This robust and versatile piece of equipment has been shown to be practical and effective in a number of industrial settings. It may be deployed from a Ridged Inflatable Boat (RIB), a larger vessel, or a jacked up wind farm construction vessel, production platform, or rig.
- Device powered by a standard 12-volt auto-marine lead-acid storage battery;
- Control unit contains a pulse generator and an amplifier, which transmits random bursts of audio frequency signals to the transducer, where it is converted into intense sound;
- 5 m long (or longer, if preferred) deployment cable allows for a safe vertical deployment;
- Deployment cable terminates with a plastic encased ceramic transducer cylinder; and,
- Apparatus housed in a robust weatherproof orange box.
Lofitech sound source
The Lofitech seal scarer produces irregular tonal harmonic sounds from 18 to 15 KHz with a sound pressure between 189 and 193 dB/µP/m.
Peer-reviewed scientific evidence shows that this is extremely unpleasant for seals and porpoises. Various controlled and replicated field trials have demonstrated the Lofitech to deter harbour seals up to 1 kilometre and porpoises up to 7.5 km.