Assessing the effectiveness of an electrical stunning and chilling protocol for the slaughter of Atlantic mackerel (Scomber scombrus)

Abstract

Inducing unconsciousness in fish using electrical stunning prior to slaughter may improve fish welfare and fillet quality if such practises can be disseminated into wild capture fisheries. The objectives of this study were to: 1) evaluate if an established slaughter protocol consisting of dry electrical stunning (using a coupled AC/DC current at ≈ 110 V rms ) followed by chilling could be used to stun the wild captured species Atlantic mackerel ( Scomber scombrus ) unconscious within 0.5 s; 2) determine if death could be induced without consciousness recovery by longer duration stunning (5 s) combined with chilling in an ice/water slurry for 6 min; and 3) examine the extent of quality defects arising from the applied slaughter protocol. We determined consciousness by examination of behavioural responses in a standardised vitality assessment. Out of a sample of 10 mackerel, 9 were assumed to be rendered unconscious by the 0.5 s stun, as determined by the presence of tonic and/or clonic muscle cramping consistent with a general epileptic insult. Assumed unconsciousness was maintained throughout chilling treatment in all fish (n = 25) following a full stun of 5 s. All fish were assumed to have died as a result of the protocol. There was no evidence of spinal damage or haematoma quality defects post filleting. These results suggest that the examined protocol is effective at slaughtering mackerel in a manner consistent with good welfare and without inducing quality defects, but further research is required to verify the unconscious condition via electroencephalogram (EEG) and before the procedure can be applied in wild capture fisheries.

A Multi-Site Assessment of Anesthetic Overdose, Hypothermic Shock, and Electrical Stunning as Methods of Euthanasia for Zebrafish (Danio rerio) Embryos and Larvae

“…While electrical stunning is a euthanasia method approved by the Directive 2010/63/ EU [1] and is used for the euthanasia of larger fish [16][17][18][19][20], it is not commonly used in zebrafish laboratories [3,9]. This is the opposite to hypothermic shock, a method used by many facilities for the euthanasia of zebrafish [3,9], but not mentioned in the European Directive.…”

The effects of electrical stunning on the nervous activity and physiological stress response of a commercially important decapod crustacean, the brown crab Cancer pagurus L.

“…This will entail a re-design of single in-air/dry stunners such as the Crustastun™ to ones based on continuous flow or conveyer belt systems. Such systems exist for fish [ 25 , 26 ], but are still at the prototype stage for crustaceans [ 33 ].…”

“…These include an initial effective anaesthetisation before killing [ 19 – 21 ] or a rapid stunning, either mechanical or electrical, that induces immediate insensibility by inactivating the nervous system [ 16 , 22 , 23 ]. Electrical stunning is used widely in the slaughter of domesticated farm animals [ 24 ], and can also be effective on aquatic animals such as fish [ 25 , 26 ]. It therefore seems to offer potential for humane killing of decapod crustaceans, and indeed a number of stunning devices have been developed for this purpose: LAVES (adapted from a fish stunner) [ 27 ], STANSTAS [ 28 ] and CRUSTASTUN™ [ 16 , 27 , 29 ].…”

Effect of different stunning methods on rigor mortis, shape, energetic status and physical characteristics of Salmo carpio fillets

“…Previous studies evidenced vertebral fractures and consequent blood spots in fillets of fishes exposed to electrical stunning, which negatively affect fillet quality. 19,51 Conversely, other authors did not evidence spinal damage or haematomas as post-filleting quality imperfections, 11,52,53 indicating that this method was properly applied in terms of voltage and exposure time. In the present study, 55% of ES fillets showed haematomas at 0 h, in line with what was observed in Chinook salmon (24-71%) 51 and Atlantic herring (60%), 19 hence highlighting the need to set specific electrical stunning parameters for S. carpio.…”