Testing the effectiveness of an acoustic deterrent device for excluding seals from Atlantic salmon rivers in Scotland

Published source details Graham I.M., Harris R.N., Denny B., Fowden D. & Pullan D. (2009) Testing the effectiveness of an acoustic deterrent device for excluding seals from Atlantic salmon rivers in Scotland. ICES Journal of Marine Science, 66, 860-864.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices on moorings Action Link

Use acoustic devices on moorings

A replicated, controlled study in 2006–2008 at two sites in the Rivers Conon and North Esk, northeast Scotland, UK (Graham et al. 2009) found that using acoustic devices reduced the number of grey seals Halichoerus grypus and harbour seals Phoca vitulina upstream of the device but did not reduce the number of seals overall. Grey and harbour seals were observed upstream of the acoustic device during fewer surveys with the device turned on (North Esk: 5 surveys; Conon: 14 surveys) than turned off (North Esk: 9 surveys; Conon: 22 surveys). However, the overall number of seals did not differ significantly with the device turned on or off (data not reported). An acoustic device (Lofitech Seal Scarer) was deployed at each of the two rivers, 2–3 m from the bank at a depth of 2 m. The devices were turned on (emitting 500 ms pulses at 15kHz) or off (silent) for alternating periods of 1–30 days in January–May 2006 at one river and October–February 2007/2008 at the other. Both rivers (38–45 m wide) supported Atlantic salmon Salmo salar stocks. Seals were observed from the riverbank with binoculars during surveys (each lasting 1–1.5 h) with the device turned on (26–28 surveys) and off (29–36 surveys).

(Summarised by: Anna Berthinussen)