Electromagnetic pulses show promise in shark deterrence for aquaculture.
Norwegian researchers have identified potential solutions to reduce shark attacks on salmon farming operations, particularly in southern and western Norway, where the spiny dogfish (Squalus acanthias) has become a recurring issue during autumn and winter months.
The study, conducted by the Norwegian Research Centre (NORCE), tested electromagnetic pulses (EM) and chemical extracts from shark skin as methods to deter sharks from entering fish pens.
Sharks Attracted by Dead Fish
Spiny dogfish are drawn to dead fish in salmon pens, causing damage to nets and attacking live fish. Despite preventive measures such as regular removal of dead fish and net inspections, current efforts have proven insufficient.
“Today, there is no effective method to prevent shark attacks on aquaculture facilities. Our project aimed to test active and passive methods that interact with sharks’ sensory systems,” said Pradeep Lal, a senior researcher at NORCE.The study involved controlled experiments in laboratory conditions at the University of Bergen and field trials in collaboration with Salarsafe AS, which has developed an electromagnetic shark protection system.
In laboratory trials, spiny dogfish measuring 60-85 cm were exposed to various stimuli, including EM pulses, orca sounds, and chemical extracts from shark skin and mackerel. While orca sounds had little effect, EM pulses and shark skin extracts triggered avoidance behavior.
Field trials reinforced these findings, with EM pulses proving effective at repelling sharks. However, orca sounds again failed to elicit a deterrent response.
Impact on Farmed Salmon
The research also assessed the effects of EM pulses on farmed salmon, with results indicating no long-term stress. “EM pulses caused temporary increases in cortisol, glucose, and lactate levels, suggesting a stress response. However, no chronic stress indicators were observed, and growth parameters remained stable,” Lal noted.
The findings suggest EM pulses and chemical extracts could provide effective shark deterrence while minimally impacting farmed salmon. Further research will focus on optimizing EM pulses for different shark sizes and hunger states and assessing long-term effectiveness in real-world aquaculture settings.
The project represents a step forward in addressing the economic and operational challenges posed by shark interactions in the aquaculture sector.
