Attempts to develop acoustic methods of keeping cape fur seals Arctocephalus pusillus from fishing nets

• Published in: Biological conservation 1981-01, Vol.21 (2), p.141-158
• Main Authors: Shaughnessy, P.D., Semmelink, A., Cooper, J., Frost, P.G.H.
• Format: Article
• Language: English
• Subjects: Arctocephalus pusillus; Marine
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/0006-3207(81)90076-8

Cape fur seals Arctocephalus pusillus cause losses to catches of pelagic shoaling fish made by purse-seine vessels off southern Africa. The seals disturb fish shoals and fish within nets, and damage nets. Weighted firecrackers, ‘Thunderflashes’, ‘Belugas’ and ‘Seal Deterrents’, that exploded underwater were used to scare seals in nets. Seals responded to playback of killer whale Orcinus orca vacalisations and sweep frequency pulses, but did not flee. Seals moved away from 0·303 in calibre rifle bullets fired into the water in their vicinity, but were unaffected by bullets fired over their heads. An arc-discharge transducer was developed to produce the underwater compression and sound levels similar to those caused by firecrackers and by 0·303 in bullets. Most seals at the cod-end of a trawl net moved away from the arc-discharger stimulus, but seals did not leave a purse-seine net. It is concluded that deterrents developed in this study were ineffective in reducing disturbances by seals at purse-seine nets.