Commercial slaughter methods used on Atlantis salmon: determination of theonset of brain failure by electroencephalography

This study investigated the effect of exsanguination without prior stunning , or carbon dioxide narcosis followed by exsanguination, or percussive stun ning or spiking the brain, on the time taken to abolish the visual evoked r esponses (VERS) Of farmed Atlantic salmon. Only percussive stunning and spi king killed the fish immediately and the other two methods resulted in aver sive reactions by the fish. The VERs were lost between 148 and 440 seconds after exsanguination without stunning, and between 300 and 554 seconds afte r carbon dioxide narcosis followed by exsanguination. During both these pro cedures the fish showed strong aversive behaviour. In contrast, percussive stunning and spiking the brain could result in the immediate loss of VERS a nd no aversive reactions from the fish if the stun was applied correctly.