Global tilapia production is estimated at 6 million tonnes (14.5 billion individuals) annually (Mood et al., 2023) . The slaughter process commonly comprises live transport, chilling followed by bleeding, descaling and evisceration. Here we report on trials investigating in-water electric stunning as a humane stunning method for tilapia. Laboratory trials were followed by a commercial trial in which an in-water electric stunner was installed in parallel with an existing live-chilling line.
Laboratory trials first focused on establishing successful stunning parameters for tilapia. This was done by establishing whether insensibility was achieved immediately at the onset of a stun using clinical and EEG assessments. Analysis of the EEG power spectrum showed a significant drop in power after the stun, similar to that observed in the same fish under terminal anesthesia. A similar drop in power has been considered indicative of unconsciousness in other species (Beyssen et al., 2004 ). The second aim of these trials was to determine an exposure duration that ensured unconsciousness persisted long enough for death to occur through bleeding.
Commercial trials were performed using the stunning parameters established in the lab. To this end, a purp ose-built stunner was installed in-line in a plant capable of processing 12 tonnes /hr. Fish were assessed for clinical signs of consciousness following the stun, and as they progressed through the processing line. There was no indication of inadequate stunning or returning consciousness. In-house quality assessment s showed no negative effects of in-water electric stunning for tilapia.
Conclusions
Tilapia are a hardy species and known for being difficult to kill. Here we have demonstrated that improved welfare through in-water electric stunning is not only possible in a small scale laboratory context, but is commercially feasible as well.
References
Mood, A., Lara, E., Boyland, N. K., & Brooke, P. (2023). Estimating global numbers of farmed fishes killed for food annually from 1990 to 2019. Animal welfare (South Mimms, England) , 32, e12. https://doi.org/10.1017/awf.2023.4
Beyssen , C., Babile , R., & Fernandez, X. (2004). Electrocorticogram spectral analysis and somatosensory evoked potentials as tools to assess electrical stunning efficiency in ducks. British Poultry Science , 45(3), 409–415. https://doi.org/10.1080/0007166041000173092