Indicators 4.1.3.2–4.1.3.5

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Indicators 4.1.3.2–4.1.3.5

by Contact on 8 October 2026

Requirement

The UoC shall ensure all fish, including fish not destined for human consumption, are stunned prior to killing according to the methods and transition periods outlined in Appendix 12 (12.4, Table 5).

The UoC shall ensure that at least 95% of the fish lose consciousness immediately after stunning, and any remaining conscious fish are re-stunned. Unconsciousness shall persist until the fish are killed

The UoC shall ensure that stunning and killing are effective by verifying the absence of all of the following: a) opercular movements; and b) eye movements; and c) body movements (except for involuntary muscular spasms); and d) reaction to a painful stimulus.

The UoC shall have measures in place to immediately respond to ineffective stunning or killing, including the presence of a back-up system, and shall implement appropriate corrective actions to prevent recurrence.

How Do I Interpret This Requirement?

  • Slaughter is generally a two-stage process:

    • The animal is first stunned to make it insensible to pain.

    • Killing is then carried out.

    • Stunning methods are required to induce immediate or rapid (less than one second) unconsciousness.

      • Ice-slurry is not an approved stunning method but can be used as a killing method after immediate or rapid (less than one second) unconsciousness.

      • Brain perforation techniques such as ‘spiking’ or ‘ikijime’, involve instruments that physically perforate the brain, causing severe and irreversible damage and leading to almost immediate stunning and death.

    • An effective stun is determined by the loss of consciousness using an electroencephalogram (EEG) measured in a laboratory, which is not practicable at a site level.

  • To ensure that at least 95% of the fish are stunned before killing, the sample size should accurately reflect the scale of the harvest operations. Variable sample sizes per harvest day may be accepted, provided that justification is given based on the specific scenarios. Stunning effectiveness should be assessed by confirming signs of unconsciousness:

    • Loss of balance or coordination.

    • Reduced or absent reflex responses.

    • Cessation of opercular movements (in succession and with rhythm).

    • Absence of eye roll.

    • The use of body movement as an indicator for the effectiveness of stunning or killing can be misleading as muscular spasms often occur in unconscious or dead fish.

  • Body movements indicating struggling, a swimming activity or efforts to remain upright or regain equilibrium are relevant movements to watch out for and that indicate consciousness. Visual assessment comparing stunned and non-stunned fish:

    • Body movements indicating struggling, a swimming activity or efforts to remain upright or regain equilibrium are relevant movements to watch out for and that indicate consciousness.

    • A back up stunning system e.g. a priest, must be available.

| | Stunned | Non-stunned |

| Movements | Muscle twitches | Flapping |

| Breathing | Gasping, | Regular opercula movements |

| | | |

| | Absent regular opercula movements | |

| Eye roll | Absent | Eye movement when rolled |

| Reactions to handling | None | Reactive |

| Reaction to tail pinch | None | Reactive |

| Swim response | Absent | Evident |

| Equilibrium | Absent | Evident |

  • The requirement to stun the fish before the killing also applies to fish not destined for human consumption e.g. wild species, cleaner fish.

  • Ensure there is no chance of recovery of consciousness before fish death:

    • Minimise the stun to kill time to less than one second.

    • Consider that stun and kill can occur together, for example, pneumatic stunning with automatic gill cutting, but they are distinct operations.

    • If there is uncertainty about whether a fish is unconscious, the stunning should be repeated or the harvest shall stop to verify stun parameters before proceeding, e.g. more than 5 fish in 10 seconds requiring backup stun.

      • Or use an alternative backup method, e.g. a priest or secondary stunner.

        • For electrical stunning, machines must adhere to manufacturers recommendations for that species, or if not available, to documented electric stunning parameters from research.

Table 10: Electrical stunning methods which have been validated in the laboratory by EEG to prove that unconsciousness was reached within 1 second.

| Species | Method | Parameters | Followed by killing method | Reference |

| Rainbow trout | In water electric stun | 30-60 seconds of 0.84 A~RMS~dm^- 2^and 10.2 V~RMS~ cm | Not detailed in report | Hjelmstedt et al (2022) |

| | | | | |

| | (two submerged stainless steel electrodes) | Stun to maintain unconsciousness: ≥30 s, the electrical field strength (10.2 VRMS cm^-1^) and the current density (0.84 ARMS dm^-1^respectively). ^-1^ | | |

| European sea bass | In water electric stun | 3.3 Arms/dm2 (sinusoidal 50 Hz or pulsed square wave AC,133 Hz, 43% duty cycle) for 10 seconds | Ice slurry | Lambooij et al (2008) |

| | | | | |

| | (electric plate) | | | |

| Turbot | Electric dry stunner with hanging electrodes | 2.3 ± 0.91 A~rms~ by applying 122.6 ± 8.0 V~rms~ for 1 second | Ice slurry | Daskalova et al (2016) |

| | | | | |

| | | Or | | |

| | | | | |

| | | 1.3 ± 0.4 A~rms~ for 1 s and 0.6 ± 0.3 A~rms~ for 19 seconds | | |

| Atlantic salmon | Electric dry stunner with hanging electrodes | A combined AC and DC supply minimum 0.5s recommended using currents of 668 mArms and ≈107 Vrms | Gill cutting* | Lambooij et al (2010) |

| Atlantic salmon | In water electric stun | high voltage stunning, using 200 V/m for 1 second | Gill cutting* | Robb & Roth (2003) |

| | | | | |

| | | or | | |

| | | | | |

| | | low voltage stunning at 50–25 V/m for 3 and 12 seconds | | |

| Nile tilapia | In water electric stun | t ~14 VRMS cm− 1 and a current density ~1.1 ARMS dm− 2 for 30 s | Gill cutting and ice slurry | Sundell, E. et al (2024) |

* Adapted killing method from reference article.

Evidence of Implementation

  • Employees should demonstrate knowledge confirming the stun and kill monitoring.

  • Records:

    • Employee training (see Appendix 12)

    • Slaughter monitoring, e.g.:

      • Verification and registration of stunning and killing.

      • Observation of signs of unconsciousness.

      • Records of the use of a backup method.

Auditors Should Confirm

  • Monitoring of stunning and slaughter in conformance to the requirements.

  • Records, employee interviews and observations of stunning and slaughter operations during the audit should demonstrate the implementation of the requirements.

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