Seal scarers as a tool to deter harbour porpoises from offshore construction sites

Published source details Brandt M.J., Höschle C., Diederichs A., Betke K., Matuscheck R. & Nehls G. (2013) Seal scarers as a tool to deter harbour porpoises from offshore construction sites. Marine Ecology Progress Series, 475, 291-302.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices to deter marine and freshwater mammals from an area to reduce noise exposure Action Link

Use acoustic devices to deter marine and freshwater mammals from an area to reduce noise exposure

A randomized, controlled study in 2010–2011 of a pelagic site in the Great Belt, Denmark (Brandt et al. 2013) found that when an active acoustic device was deployed, fewer harbour porpoises Phocoena phocoena were sighted within 1 km of the device. The average number of porpoise sightings was lower with the acoustic device turned on than turned off at distances of 0–150 m (0 vs 2 sightings/4h respectively), 151–450 m (0 vs 8 sightings/h) and 451–1,000 m (0.3 vs 20 sightings/h) from the device. Six porpoises also avoided the active device at distances of 1.1–2.4 km, and six porpoises had no obvious reaction at distances of 2.1–3.3 km (see original paper for details). In May–August 2010, an acoustic device (Lofitech Seal Scarer) was tested by deploying it from an anchored boat 150 m offshore, 4 m below the surface in water 2–15 m deep. The device was randomly turned on (emitting 0.6 second pulses at 14.5 kHz with random pauses of <1–90 seconds) or off (silent) during a total of seven and four days respectively. Porpoises within 1 km were observed and tracked with a theodolite from a cliff. Additional observations were made during three days in September 2010 and one day in August 2011, in which the device was deployed 1.1–3.3 km offshore and activated for 15 x 5-minute intervals.

(Summarised by: Anna Berthinussen)