Assessing effectiveness of electrical stunning and chilling in ice water of farmed yellowtail kingfish, common sole and pike-perch

Animals should be rendered unconscious before slaughter in order to avoid suffering or pain. The objective of this study was to evaluate an electrical stunning after dewatering to induce instantaneous unconsciousness and insensibility in yellowtail kingfish (Seriola lalandi), common sole (Solea solea) and pike-perch (Stizostedion lucioperca). To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 10 min. Loss of consciousness and sensibility were assessed by neural (EEG), physiological (ECG) and behavioural parameters. An epileptiform insult was observed in all yellowtail kingfish (n = 27), common sole (n = 25) and pike-perch (n = 25) after administering a current of 0.54 ± 0.12 Arms (124 V dc and 11 Vrms ac; 100 Hz), 0.65 ± 0.23 Arms (98 V dc and 8.4 Vrms ac; 100 Hz) and 0.75 ± 0.24 Arms (144 V dc and 13 Vrms ac; 100 Hz) during 1 s through the head of individual fish, respectively.When yellowtail kingfish (n = 11) was submitted to a 5 s electrical stun followed by chilling in ice water, this resulted in passing 0.72 ± 0.13 Arms for 5 s and no recovery during chilling. In the case of common sole (n = 10) and pike-perch (n = 12), passing 1.4 ± 0.64 and 0.75 ± 0.24 Arms during 5 s followed by chilling in ice water for 10 min resulted in an irrecoverable stun in 9 out 10 fish and 11 out 12 fish, respectively. We conclude that for yellowtail kingfish the investigated combination of electrical stunning and chilling is suitable for humane slaughter, whereas for common sole and pike-perch this procedure needs to be optimised.

► We evaluate the technical requirements of a dry electrical stunning in farmed fish.
► One-second dry electrical stunning induces tonic clonic seizure in all fish.
► Stunning for 5 s and chilling is suitable for humane slaughter in yellowtail kingfish.
► In common sole and pike-perch this procedure needs to be optimised.