Comparision of two slaugthering procedures in rainbow trout (Oncorhynchus mykiss)

Jorge Diaz-Villanueva, Hugo Robotham


The traditional slaughter procedure of rainbow trout (Onconrhynchus mykiss) by automatic stunning followed by bleeding by cutting gills was compared with an alternative slaughter procedures which involves rapid decreasing temperature (-3.5°C) by immersion in flow-ice without gill bleeding. Muscle pH was measured as an indicator of stress achieved during confinement and sacrifice phases. The capacity of blood retention in the gut and head is proposed as potential sources to assess biosecurity. The average weight of gut and head per fish with the alternative method was 24.4 g higher than the traditional method, equivalent to 1.04% of the body weight of an average specimen. The alternative method accumulated 5.3% more weight in gut per fish than the traditional method and 4.9% more in the head weight than the traditional method. The amount of blood retained in the gut and head with the alternative method represented 44.6% of total shed by the traditional method. For a forecast of 900,000 ton of salmonids in 2014, the blood retained in gut and head was estimated in at least 9,630 ton. No significant differences in muscle pH between the two methods were observed. The pH of the fish in the confinement point was equal to 7.06 decreasing approximately to 6.5 in the sacrifice phase independent of the method employed. The alternative method does not produce instant death of the fish; however, it has more capacity than the traditional method to retained blood in gut and head to be used in increasing biosecurity and if combined with more efficient methods to achieve rapid unconsciousness, e.g. electrical stunning, we would have a combined sacrifice method useful to improve current methods. The proposal for more efficient and effective slaughter methods of fish is an open issue that requires further investigations.

Diaz-Villanueva J, Robotham H. Comparision of two slaugthering procedures in rainbow trout (Oncorhynchus mykiss). Lat. Am. J. Aquat. Res.. 2017;43(2): 287-294. Available from: doi:10.3856/vol43-issue2-fulltext-3 [Accessed 28 Jan. 2023].
Diaz-Villanueva, J., & Robotham, H. (2017). Comparision of two slaugthering procedures in rainbow trout (Oncorhynchus mykiss). Latin American Journal of Aquatic Research, 43(2), 287-294. doi: