Louse deterrent could affect marine mammals

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Pål Mugaas Jensen 

Ultrasound has been shown to have an effect on different biofouling organisms, and studies on barnacles indicate that it may also be efficient against the attachment of salmon louse copepodids on host fish. Indeed, the system has been trialled, with some success, by the Norwegian salmon producer Salaks on a commercial scale for the last two years.

However, according to a new report by Nofima: "The use of ultrasound to combat sea lice may conflict with regulations for Aquaculture Stewardship Council (ASC) certification of salmon farms...There are reasons to believe that ultrasound will have the same effect on seals and other marine mammals as traditional seal deterrents".

"Different types of seal can detect ultrasound to about 100 kHz (Turl, 1982), while some whales can hear ultrasound up to 280 kHz (Wood & Evans, 1980). There is no doubt that seals and whales can hear ultrasound at around 20 kHz, which is what is most appropriate for combating sea lice".

The environmental organisation Naturvernforbundet wants more research before they conclude whether this is acceptable.

"We might assume that ultrasound could be better than the huge and unacceptable use of chemicals against sea lice, which leads to resistance and pollution in our ecosystems. But other adverse aspects of the use of ultrasound is little known to us, and therefore we believe much more research is needed before concluding," the organisation's Technical Supervisor for biodiversity in Naturvernforbundet, Arnodd Håpnes (pictured), told www.kyst.no

"It is known that marine mammals in particular are sensitive to sound, but that fish and other marine organisms may be sensitive, - for example in connection with seismic activities. Research shows that sound energy from seismic activities can kill larvae and do damage to the hearing, kidneys, heart and swim bladders of adult fish," he said.