Electrical stunning and killing of Atlantic salmon

Abstract

Atlantic salmon (Salmo salar) at various size 226-1938 g were placed in electric dry stunning either tailor head- first and then exposed to 50 Hz, 240 V AC for 0.5 and thereafter 9.5 s of electricity. This to verify whether the animal is rendered unconscious prior to killing by immersing the animal into cold brine (-14 to -18 °C) or hypoxic water, supersaturated with CO2. In addition, salmon from 2000 to 5000 g were exposed to head stunning only. Behaviour, heart (ECG) and brain (EEG) activity were monitored until animal was classed as dead. Post the treatment, the internal temperature of the animal was measured placing loggers into the neuro and heart cavity. The electric potential across the brain was also measured. A preliminary evaluation of the EEG and ECG registrations in the individual fish showed that loss of consciousness can be induced within 0.5 second and consciousness can be prolonged without recovery when the cold brine or seawater saturated with carbon dioxide is applied as killing method. Our results also suggest that the current can be applied head to tail, which facilitates immediate stunning of Atlantic salmon in a commercial setting. We conclude that electrical stunning in combination with cold brine is effective for humane stunning and killing Atlantic salmon.