A humane protocol for electro-stunning and killing of Nile tilapia in fresh water

• Published in: Aquaculture
• Main Authors: Lambooij, E., Gerritzen, M.A., Reimert, H.G.M., Burggraaf, D., van de Vis, J.W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: anguilla-anguilla l; catfish clarias-gariepinus; consciousness; fish; pain; quality; slaughter; Slaughter; Anguilla anguilla
• Online Access: https://research.wur.nl/en/publications/a-humane-protocol-for-electro-stunning-and-killing-of-nile-tilapi; https://doi.org/10.1016/j.aquaculture.2008.01.026

Behavioural, neural and physiological parameters were scored after electro-stunning of Nile tilapia (Oreochromis niloticus) in three positions to an electric field in fresh water. An overall current density, 1.0 Arms/dm2, 50 Hz sinusoidal, applied for 1 s top-to-bottom in water (700 ¿S/cm), induced a general epileptiform insult on the EEG for 26 ± 10 s (n = 24). The ECG revealed fibrillation for 9 ± 4 s in 15 out of 24 fish. To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 15 min. Killing of the stunned fish by gill-cutting instead of chilling is not recommended, as 2 out 4 tilapias responded 10 min post stun. When electricity was applied head-to-tail on tilapia (n = 8), the overall current density could be reduced to 0.4 Arms/dm2, 50 Hz sinusoidal, to induce a general epileptiform insult, which lasted 27 ± 10 s. A pulsed square wave alternating current (overall density of 0.6 Arms/dm2, 133 Hz and 43% duty cycle) was applied for 1 s side-to-side on tilapia in water (650 ¿S/cm). This induced a general epileptiform insult for 51 ± 37 s (n = 14). Fibrillation occurred for 16 ± 7 s (n = 10). Free-swimming fish righted between 68 and 95 s (n = 5) and between 438 and 1139 s (n = 5) after 1 and 5 s electro-stunning, respectively. Our results show that protection of welfare of tilapia at slaughter can be obtained with electro-stunning followed by killing the stunned fish in ice water.