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

• Published in: Aquaculture 2008-03, Vol.275 (1-4), p.88-95
• Main Authors: Lambooij, E., Gerritzen, M.A., Reimert, H., Burggraaf, D., van de Vis, J.W.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal aquaculture; animal handling; Animal productions; Animal, plant and microbial ecology; Aquaculture; Biological and medical sciences; Chilling; electric field; Electric fields; Exsanguination; fish culture; fish fillets; Fishing industry; Flesh quality; food quality; Fresh water ecosystems; Freshwater; freshwater aquaculture; Freshwater ecology; freshwater fish; Fundamental and applied biological sciences. Psychology; General aspects; gills; muscle contraction; muscle tissues; Nile tilapia; Oreochromis niloticus; Protocol; Sinusoidal and pulsed electrical stunning; slaughter; Synecology; Tilapia; tilapia (common name); Welfare
• ISSN: 0044-8486; 1873-5622
• DOI: 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 μS/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 μS/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.